THEP Seminars

Invited external speakers tell us about recent hot topics in particle physics and cosmology.

This series started from the fall semester in 2013.  More than 100 seminars and colloquia have been already presented in CAU for the last years.

The purpose of the THEP seminars is to provide a general introduction to students and researchers and leave an ample time of discussion between speaker and participants. Anyone can download talk files from the previous seminars in the webpage. Please be aware of etiquette and responsibility in taking the content of talk files for personal uses.

Seminar takes place in 104-212 or 310-B113-1 on Thursdays at 4pm, (except the colloquium which takes place in 102-106 on Mondays at 4:30pm). 

The most beautiful experience we can have is the mysterious. 

It is the fundamental emotion that stands at the cradle of true art 

and true science. Whoever does not know it and can no longer

wonder, no longer marvel, is as good as dead. 

                                                                -  A. Einstein

Some statistics

- How many seminars in which field of particle physics and cosmology?

Beyond SM 

Dark matter

Inflation

Cosmic Microwave Background

Baryogenesis & Phase transition

Axion

Composite Higgs

Collider physics & Excesses

Strings & Gravity

Field theories & EFT

Extra dimensions

Gravitational waves

Neutrinos

Leptogenesis

= = = = = = =

Seminars in fall 2025

186. Dec 11, TBA

185. Dec 4, TBA

184. Sept 29, 30, Oct 2, TBA

Seminars in summer 2025

183. Aug 13 (2pm, 102-110), Hiroki Takahashi (Tokyo Univ), Exploring chirality structure in nucleon decay.  talk file.

Abstract:

The search for baryon number violation offers a promising path to uncovering new physics. In this talk, we examine how measurements of different nucleon decay channels can shed light on the underlying theory. We first investigate the chirality structure of baryon-number-violating interactions through lifetime measurements of strangeness-conserving nucleon decay modes. Using an effective field theory framework, we show that the ratio of partial decay widths—specifically, Γ(p→ηℓ+)/Γ(p→π0ℓ+), where ℓ+ denotes a positron or anti-muon—is sensitive to this chirality structure. Moreover, we find that in certain new physics scenarios, decay channels involving both anti-leptons and anti-neutrinos can provide complementary insights into their structures. These results underscore the importance of searching for various decay modes in future nucleon decay experiments. If time permits, we also discuss how the ratios of branching fractions can be useful to determine an unknown unitary matrix in the flipped SU(5) grand unification.

Seminars in spring 2025

182. June 5 (4pm, 102-110), Prof. Jeong Han Kim (Chungbuk National Univ), Echoes of Self-Interacting Dark Matter from Binary Black Hole Mergers.  talk file.

Abstract:

The idea that dark matter (DM) can self-scatter over cosmological timescales – altering the structure of DM halos – has been widely studied as a potential solution to observational challenges such as the diversity problem in dwarf galaxies. While self-interacting dark matter models have been explored across scales ranging from dwarf galaxies (∼pc) to galaxy clusters (∼Mpc), there has been little exploration of self-interaction effects at even smaller scales using higher-resolution probes. In this work, we investigate a system composed of a DM spike surrounding an intermediate-mass black hole, accompanied by a lighter black hole (e.g., a solar-mass black hole) captured into an inspiral. We show that DM self-interactions can modify the spike profile in a way that alters the gravitational wave (GW) signal–a change potentially detectable by LISA. This opens a new window for probing DM self-interaction properties at extremely short distances, starting from the spike radius (at ∼ pc) down to the size of binary black hole systems (at ∼ 10^(−8) pc).

181. May 29 (4pm, 310-B113-1), Dr. Minxi He (IBS CTPU-PTC), Geometry of target space and unitarity of Higgs inflation.  talk file.

Abstract: 

The Higgs inflation is well-motivated by particle physics and gives predictions on cosmic microwave background favored by the Planck experiment. However, the validity of this model as an effective field theory is jeopardized by its low UV cutoff and the preheating dynamics. Due to the multi-field nature of this model, the UV cutoff is determined by the geometry of the target space (given the self-coupling is small) as in the non-linear sigma model, which is independent of field redefinition. However, this uniqueness is obscured by the freedom of redefinition of the spacetime metric in the presence of gravity. To unambiguously calculate the cutoff scale, we propose an extended target space whose geometry is independent of the conformal transformation of the spacetime metric. I will discuss the application of this new method to the Higgs inflation in the metric and the Einstein-Cartan formalism. I may also briefly discuss the preheating process. 

180. May 7 (4:30pm, 102-110), Prof. Seung J. Lee (KIAS), Cosmological quasiparticles and the cosmological collider, HEP center seminar.  talk file.

Abstract:

In this talk, I will introduce the intriguing interplay between cosmology and strongly coupled dynamics, showing how temporary spectral features can leave lasting, observable imprints on the primordial fluctuation spectrum. Focusing on nearly conformal extensions of the Standard Model and employing AdS/CFT reasoning, I will demonstrate the emergence of gapped structures and distinct particle-like peaks in the scalar operator's spectral density within an inflationary setting. I will then estimate their contribution to cosmological observables, emphasizing unique, potentially detectable phenomena for future experiments, such as displaced oscillations in the squeezed bi-spectrum, originating from both fundamental and composite particles, and briefly touch upon the link between conformal symmetry breaking stabilization and these spectral signatures.

179. April 3 (4pm, zoom), Prof. Valerie Domcke (CERN), Hunting for stochastic gravitational wave backgrounds.  talk file.

Abstract:

Due to their extremely weak interactions, gravitational waves are a very promising, but also challenging, probe of the early Universe.  In this talk I will review the status of gravitational wave searches across different frequency bands, including the growing evidence for a stochastic gravitational wave background at pulsar timing arrays and data analysis challenges in next-generation interferometers. I will also discuss new ideas to search for gravitational waves at MHz and GHz frequencies. 

Seminars in winter 2024-2025

178. Feb 13 (2pm, 104-212), Prof. Kang Sin Choi (Ewha Womans University), Renormalization, decoupling and the hierarchy problem.  talk file.

Abstract:

We present a detailed renormalization of scalar mass loop corrections, faithfully taking into account the counterterms. Our work shows that top quark contributions exhibit power-law running. Furthermore, we demonstrate that heavy fields in loops naturally give suppressed contributions to renormalized masses, consistent with the decoupling theorem.

177. Jan 20 (2pm, 104-212), Dr. Reginald Christian Bernado (APCTP), Gravitational wave science with pulsar timing arrays, and what lies ahead.  talk file.  

Abstract:

I will highlight recent progress on pulsar timing arrays (PTAs) and the potential of PTAs to constrain gravitational physics in the nanohertz regime. Specifically, I will discuss my contributions to modeling the gravitational wave background signal, testing its Gaussianity, understanding the cosmic variance in PTA observations, and developing software to maximize the scientific output of PTAs, especially in light of forthcoming Square Kilometer Array observations.

Seminars in fall 2024

176. Dec 12 (4pm, 104-212), Prof. Joern Kersten (Bergen/Yonsei), Dark Matter at the End of 2024.  talk file.

Abstract:

I will review the current status of Dark Matter candidates, searches, and open issues. Afterwards I will present a particular scenario in more detail where sterile neutrino Dark Matter is produced in scattering processes with Standard Model neutrinos, which lead to a period of exponential growth in the Dark Matter abundance.

175. Dec 5 (4pm, 104-212), Prof. Eung Jin Chun (KIAS), Spontaneous leptogenesis by majoron dark matter.  talk file.

Abstract:

In this talk, we will briefly review the problem of baryon asymmetry of the Universe and the idea of the standard leptogenesis linked to the seesaw mechanism explaining tiny masses of neutrinos.  Then,  we will discuss the mechanism of spontaneous leptogenesis which can work successfully with a light majoron whose coherent oscillation constitutes dark matter of the Universe.

174. Nov 14 (4pm), Dr. Yohei Ema (Minnesota/CERN), Cutting rule for in-in correlators and cosmological collider, zoom seminar.  talk file.

Abstract:

We derive a cutting rule for equal-time in-in correlators including cosmological correlators based on Keldysh r/a basis, which decomposes diagrams into fully retarded functions and cut-propagators consisting of Wightman functions. Our derivation relies only on basic assumptions such as unitarity, locality, and the causal structure of the in-in formalism, and therefore holds for theories with arbitrary particle contents and local interactions at any loop order. As an application, we show that non-local cosmological collider signals arise solely from cut-propagators under the assumption of microcausality. Since the cut-propagators do not contain (anti-)time-ordering theta functions, the conformal time integrals are factorized, simplifying practical calculations.

173. Oct 31 (4pm, 104-212), Dr. Jong-Hyun Yoon (Chungnam National Univ), Modern Computational Approaches to Early Universe Modeling.  talk file.

Abstract:

In physics, while analytical calculations remain appealing, there are situations where the use of computers becomes indispensable. A straightforward example is the three-body problem, where even the interactions of just three bodies are challenging to solve analytically. This necessity is similarly evident in studies of the early universe. Understanding the dynamics of the inflaton requires numerical analysis through lattice simulations in this context. Accessing high-performance computing (HPC) used to be difficult, but it is now widely available and significantly more powerful. We apply numerical results obtained through HPC to various physical problems, including the dark matter problem. However, practical constraints still hinder our ability to fully simulate the early universe, so we are exploring machine learning as a means to overcome these challenges.

172. Oct 16 (4pm, 103-305), Dr. Liliana Kersten (Sogang Univ), The dawn of Gravitational Waves from particle physics processes, HEP center seminar & snail lecture.  talk file.

Abstract:

The first ever direct detection of a gravitational wave (GW) signal in 2015 opened the era of gravitational wave astronomy and revived interests in GW of stochastic origin. Among the stochastic signals are those corresponding to particle physics processes of cosmological origin, that is the early universe. In this seminar, in the first part, I will introduce stochastic GW of the early universe, ranging from First Order Phase Transitions, topological defects and GW from the Standard Model plasma.

In the second part of the seminar, I will talk about how the GW from the Standard Model plasma is a very useful way to constrain the reheating temperature of the universe but only in extended theories of gravity. I will also mention prospects of detection of this kind of GW and in general of detection of GW of stochastic origin.

Time table:

4:00-4:50pm  Introduction to GWs in the early cosmology

4:50-5:10pm  Break

5:10pm-6:00pm Gauss-Bonnet models and GWs

6:20pm-8:00pm Dinner

171. Oct 14 (4:30pm, 102-805), Prof. Kiwoon Choi (IBS CTPU), Exploring Fundamental Physics with Axions,  department colloquium.

Abstract:

Axion is a hypothetical very light and very weakly interacting spin-0 particle which has been postulated to solve the several important issues in fundamental physics, including the strong CP problem of the Standard Model of particle physics and the origin of the dark matter in our Universe. Its theoretical origin may also shed light on fundamental theories incorporating quantum gravity, such as string theory. In this talk, I first describe the current status of fundamental physics and motivate axions from various perspectives. I then present some of the on-going or planned experimental efforts to discover axions and measure their physical properties, including the experimental activity at the Institute for Basic Science (IBS). Finally I discuss what can be learned about the underlying theory of axions from the experimentally measured properties of axions.​ 

170. Sept 28 (1:30pm, KIAS), Dr. Tae Hyun Jeong (IBS CTPU),  Phase transitions in the early universe

169. Sept 19 (4pm, 104-212), Dr. Shuntaro Aoki (IBS CTPU), Cosmological collider from multiple scalars and $R^2$ gravity. talk file.

Abstract:  Cosmological collider signals of primordial non-Gaussianity arise at tree level when an extra scalar has Hubble mass during inflation. We critically review the formalism finding that a large class 

of inflationary theories, based on Planck-scale physics, predict a scalar bi-spectrum around the gravitational floor level. This mild signal arises for example in $R^2$ gravity, in the regime where its gravitational scalar has Hubble-scale mass. Signals much above the gravitational floor  arise in theories where scalars undergo multiple turns during inflation, thanks to sub-Planckian physics.

References: arXiv:2408.07069

Seminars in summer 2024

168. Aug 23 (2pm in 102-206), Dr. Kuldeep Deka (New York Univ Abu Dhabi), Thermal Dark Matter and the impact of low temperature reheating.

Abstract: Despite decades of experimental efforts, the nature of dark matter (DM) remains elusive. The hypothesis that DM consists of weakly interacting massive particles (WIMPs) in thermal equilibrium with the standard model (SM) has been a major focus, yet no definitive evidence supports WIMP DM. This has spurred interest in other thermal production mechanisms, such as strongly interacting massive particles (SIMPs), elastically decoupling relics (ELDERs), and cannibals, where DM self-interactions are crucial. We examine the production of these thermal DM candidates during cosmic reheating, using a general parametrization for the scaling of inflaton energy density and SM temperature. We analyze the requirements for kinetic and chemical DM freeze-out in a model-independent manner. For each mechanism, we identify up to two solutions that match the observed DM relic density for a given reheating scenario and DM mass. In a simple model where DM interacts through contact interactions, we find that low-temperature reheating allows for a wider range of couplings and larger masses than in the usual instantaneous high-temperature reheating. WIMP masses can reach up to $10^{14}$ GeV, while SIMP and ELDER masses can reach up to $10^{13}$ GeV. However, cannibal solutions are still not allowed, consistent with high-temperature reheating scenarios. Current experiments already constrain this parameter space, and next-generation experiments could further probe these scenarios.

167.  Aug 21 (2pm in 310-B113-1),  Dr. Jaehoon Jeong (KIAS), Vetoing all the Higgs imposters in $H \rightarrow \ell^- \ell^+ Z$.  talk file.

Abstract:

We develop an effective and methodical algorithm for the construction of general covariant four-point $H\ell\ell Z$ vertices, accommodating leptons $\ell=e, \mu$, and designed to handle a boson $H$ of any integer spin, not merely confined to spins up to 2. While our numerical analysis assumes the $H$-boson mass to be $m_H=125\,{\rm GeV}$, the analytical framework we propose is versatile, enabling the examination of various mass as well as spin scenarios. These meticulously devised general covariant four-point $H\ell\ell Z$ vertices are pivotal in vetoing all the imposters of the Standard Model Higgs boson holding the spin-0 and even-parity quantum numbers, especially in one of its primary decay channels, the three-body decay process $H\to \ell^-\ell^+ Z$, observable at the Large Hadron Collider. Our innovative strategy encompasses the analysis of all the effectively allowed scenarios, extending beyond the limitations of previous investigations on the Higgs spin and parity determinations in the decay $H \to \ell^-\ell^+ Z$. Based on the significantly expanded scheme, we demonstrate that the Higgs boson imposter of any spin and parity can be definitively vetoed by leveraging threshold effects and angular correlations, even though achieving such conclusive results in practical and exhaustive analyses necessitates high event rates.

Seminars in spring 2024

166. May 30 (4pm in 310-B113-1), Prof. Wan-Il Park (Jeonbuk National Univ), The minimal cosmological standard model with the axi-majoron.  talk file. 

Abstract: 

I will introduce the minimal cosmological standard model which we have proposed recently.

The model combines the idea of the DFSZ axion model with the singlet Majoron model in the minimal manner, 

based on U(1)-PQ symmetry in the matter sector and the full scale invariance.

I will show that, in the presence of the non-minimal U(1)-PQ breaking term in the gravity sector, 

the model can address simultaneously most of big puzzles of particle cosmology in its minimal structure.

Some of observational imprints will also be discussed briefly.

165. May 29 (5pm in 102-108), Dr. Sungwook Hong, 거대한 우주의 구조로부터 거대한 우주의 역사를 이해하다, HEP Center seminar.

초록:

인간은 문명의 초창기부터 꾸준히 우주의 모습과 역사, 그리고 그 안에서의 인간의 위치에 관해 관심을 가져왔지만, 우주론이 체계적인 과학 연구의 대상이 된 것은 불과 100여 년 정도에 지나지 않는다.

그럼에도 불구하고, 그 짧은 기간 동안 현대 우주론은 눈부신 발전을 거듭했으며, 특히 우주에 펼쳐져 있는 수천만 광년 이상의 규모에 해당하는 소위 '우주 거대 구조'에 대한 통계 분석은 이러한 현대 우주론의 발전에 커다란 이바지를 하였다.

본 강연에서는 우주 거대 구조를 이용한 우주론 연구가 어떻게 진행되고 있는지를 간략하게 소개한다.

특히 한국 천문학계가 참여 및 수행하고 있는 관측 프로그램이나 거대 컴퓨터 시뮬레이션 등을 집중해서 소개한다.

164. May 23 (4pm), Prof. Francesco Riva (Univ Genera), Microscopic Bounds on Macroscopic Theories, on zoom.  talk file.

Abstract:

I will discuss Effective Field Theories that can originate from microscopic unitary theories, and their relation to moment theory. I will show that massive gravity, theories with isolated massive higher-spin particles, and theories with very irrelevant interactions, don’t posses healthy UV completions.

163. May 16 (4pm in 310-B113-1), Dr. Suruj Jyoti Das (IBS CTPU), Gravitational wave imprints of physics beyond the Standard Model.  talk file.

Abstract:

The origin of dark matter(DM) and the baryon asymmetry of our Universe have been two of the most long-standing puzzles of particle physics and cosmology, hinting towards some new physics beyond the Standard Model. While the quest for the conventional WIMP DM at several direct search and collider experiments has not led to any positive results so far, the high scale of asymmetry generation through leptogenesis is out of direct reach of any current experiments. In this regard, cosmological gravitational waves may provide a novel alternate window into such early Universe physics. I will discuss DM scenarios beyond the conventional WIMP paradigm, with their imprints on the cosmological gravitational wave(GW) background from inflation, topological defects and primordial black holes. The shape of such GW spectrum is dictated by the DM phenomenology and/or the scale of leptogenesis. Possible explanations and implications of the stochastic GW background signal at nano-Hz frequencies, reported recently by several pulsar timing array experiments will also be discussed.

162. April 8 (4:30pm in 102-106), Prof. Myeonghun Park (Seoultech), 입자물리학과 컴퓨터과학 (What I cannot create, I do not understand), department colloquium.

161. March 23 (1-6pm), Prof. S. M. Lee (Seoul National Univ), S-matrix and gravitational waves, Snail lecture series, Seoul National University (28-103). 

Seminars in winter 2023-2024

160. Feb 28 (6pm, zoom), Dr. Anna Tokareva (UCAS), UV-IR connections in scattering amplitudes: power of unitarity and causality, Proca seminar.  talk file.

Abstract:  

Very basic assumptions about the structure of the fundamental theory describing the nature at high energies can allow for a set of valuable constraints on the low energy EFT. This approach provides constraints that are independent of the concrete underlying fundamental theory at high energies. The low energy physics is bounded from the set of quite natural assumptions about the structure of the full theory, such as unitarity, causality and Lorentz invariance. In this talk I will consider the EFT of photons (or other U(1) gauge field) and compare different approaches to obtain bounds on its Wilson coefficients. I will present an analytic derivation of the implications of unitarity (linear and non-linear positivity bounds) and compare these constraints with the requirement of causal propagation of the photon modes around non-trivial backgrounds generated by external sources. I will show that the low energy causality condition can give complementary constraints to the positivity bounds. Applying both constraints together can significantly reduce the allowed region of the photon EFT parameters. Besides constraints on the IR theory, the analyticity and unitarity assumptions can set bounds on the UV theory. I will show this connection using the example of the graviton mediated scattering amplitudes. Surprisingly, the form of the forward limit singularities at low energies can give an insight into the of high energy limit of graviton scattering described by the unknown physics. 

159. Jan 15 (4pm, 102-110), Dr. Jongkuk Kim (KIAS), Recent B->Knunu and muon (g-2) anomalies, HEP Center seminar.

Abstract: 

Belle II collaboration recently announced that they observed B → Kνν decay process for the first time. This channel is theoretically very clean. They reported that there is 2.8σ deviation from the Standard Model expectation. Last year, Fermilab released new data on muon (g − 2) deviated from the Standard Model prediction with 5σC.L.. In this talk, I would like to focus on the simplest UV-complete U(1)Lµ−Lτ -charged Dark Matter (DM) model. Thanks to the existence of both Dark Higgs and Dark Photon in the dark sector, we can resolve DM relic density and the enhancements reported by both BelleII and Fermilab experiments simultaneously without any modification of the history of the Universe.

158. Jan 3 (2pm, 310-B113-1), Dr. Jae Hyeok Chang (Fermilab/University of Illinois Chicago), 1) Gravitational wave signatures from reheating. 2) Dark Solar Wind.  talk file.

Ref. https://arxiv.org/abs/2305.09712 ,  https://arxiv.org/abs/2205.11527

Seminars in fall 2023

157. Nov 30 (at 4:30pm), Prof. Kwang Sik Jeong (PNU), Cosmological effects of Peccei-Quinn symmetry breaking on QCD axion dark matter.  talk file.

Abstract: 

We study cosmological effects of explicit Peccei-Quinn breaking on the QCD axion dark matter. We find that the axion abundance decreases or increases significantly depending on the initial position, even for a tiny Peccei-Quinn breaking that satisfies the experimental bound of the neutron electric dipole measurements. If the axion first starts to oscillate around a wrong vacuum and if it gets trapped there until the false vacuum disappears due to non-perturbative QCD effects, its abundance increases significantly and is independent of the decay constant. Thus, the axion produced by

the trapping mechanism can explain dark matter even when the decay constant is close to the lower limit due to stellar cooling arguments. On the other hand, if the axion starts to oscillate about a potential minimum close to the low-energy vacuum, its abundance is significantly reduced because of the adiabatic suppression mechanism. This relaxes the upper limit of the axion window to large values of the decay constant.

156. Nov 17 (at 2:00pm, 310-B113-1), Prof. Deog Ki Hong (PNU), Search for axion dark matter in the laboratory and in the cosmos.  talk file.

Abstract:

I would like to present a new experimental proposal, called LACME,  to search for axion dark matter in the laboratory. If axions or axion-like particles are  the main component of dark matter, they will modify the transport property of electrons and also the atomic spectra, which will give a new way of detecting axions or axion-like particles. Finally I will discuss a topological soliton made of axions and discuss its observational consequences in the cosmos.

155. Nov 16, Prof. Jinn-Ouk Gong (Ewha Womans Univ), Recent studies on gravitational waves.  talk file.

Abstract:

I will present 3 recent studies of mine regarding non-linear aspects of cosmological gravitational waves (GWs), 1) gauge dependence of induced GWs, 2) scalar-tensor coupling due to local coordinate redefinition, and 3) tensor trispectrum in alpha-vacuum.

154. Nov 2, Prof. Sungwoo Hong (KAIST), Generalized Global Symmetries of Axion and Axion Domain Wall Problem.  talk file.

Abstract:

In the first part of the talk, I give an introductory discussion of generalized global symmetry. 

I will take the axion-Maxwell theory as an example to illustrate the points. Axion-Maxwell theory exhibits 

various generalized symmetries, including 0-form, 1-form, 2-form and non-invertible symmetries.

In the second part of the talk, I will discuss the axion domain wall problem in light of generalized symmetry.

In particular, I will show that the domain wall problem is more severe than conventionally thought 

if the global structure of the gauge group is non-trivial. Potential solutions to this "Non-invertible Axion Domain Wall Problem" will then be described. 

153. Oct 11 (Wed at 5:00pm, 102-110),  Prof. Tae Jeong Kim (Hanyang University), Top quark at the new physics frontier, CAU HEP center seminar.  talk file.

Abstract :

The Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) is the unique machine that allows us to search for new physics beyond the standard model.

The top quark is the heaviest particle in the standard model, which is still believed to play a leading role in this journey.

It has been almost 30 years since the top quark was discovered at the Fermilab Tevatron. Now more than 120 million top quark pairs were produced at the LHC only during the Run 2 period. I will present the properties of the top quark and possible new physics searches in the top quark sector.

152. Sept 18 (Mon at 4:30pm, 102-106),  Prof. Sang Min Lee (SNU), 산란진폭 - QCD부터 중력파까지, Scattering Amplitudes from QCD to gravitational wave, department colloquium.

Abstract:

산란진폭은 양자역학 및 양자장론에서 가장 기본이 되는 물리량 중 하나이다. 산란진폭 계산의 방법론으로 파인만 다이어그램이 널리 알려져 있다. 하지만, 최신 가속기 실험이 요구하는 정밀도에 도달하기 위해서는 파인만 다이어그램 이상의 다양한 기법이 필요하다. 본 강연은 산란진폭의 기본 개념을 되짚어 본 후 21세기 들어 급격히 발전한 산란진폭 관련 이론과 응용 분야를 물리학 전공 학부생 수준에서 간단히 설명하고자 한다. 입자물리학과는 동떨어져 보이는 중력파 계산에 산란진폭 연구가 어떻게 도움을 주었는지도 소개하고자 한다. ​

Seminars in spring 2023

151. June 22, Dr. Shinsuke Kawai (SKKU), Primordial black holes and gravitational waves from inflation motivated by supergravity and superstrings.  talk file. 

Abstract

In relation to the successful direct detection of gravitational waves by LIGO/Virgo, the mechanism of formation of primordial black holes (PBH) and the associated gravitational waves has been actively studied. In this talk, I would like to discuss the possibility of PBH formation in inflation models motivated by supergravity and string theory, the observational constraints, and the detectability by future gravitational wave interferometers.

150. May 25 (102-110), Dr. Tae Hyun Jung (IBS CTPU), Bubble-assisted leptogenesis.  talk file.

Abstract:

The typical mass scale of the lightest right-handed neutrino (RHN), in the thermal leptogenesis paradigm, is bounded from below at about 10^{11} GeV due to a ``strong washout'' of the final asymmetry without a tuning of parameters. In this seminar, I will explore the possibility of embedding thermal leptogenesis within a first-order phase transition (FOPT) such that RHNs remain massless until a FOPT arises. Their sudden and violent mass gain allows the neutrinos to become thermally decoupled, and the lepton asymmetry generated from their decay can be, in principle, free from the strong wash-out processes that conventional leptogenesis scenarios suffer from, albeit at the cost of new washout channels. We numerically quantify to what extent such a framework can alleviate strong-washout effects and we find the lower bound on the RHN mass, M_N ~ 10^{7} GeV, below which bubble-assisted leptogenesis cannot provide an enhancement. We also study the signature possibly observable at GW terrestrial interferometers and conclude that bubble-assisted leptogenesis models with relatively light masses, M_N < 5*10^9 GeV may be probable.

149. May 24 (102-110), Dr. Pankaj Saha (Seoultech), Reheating after Inflation: Characteristics and Constraints. CAU HEP center seminar.  talk file. 

Abstract: 

Reheating is the phase after inflation when the inflaton decay to produce all the matter and radiation in the Early Universe. 

This phase is relatively unexplored due to the lack of direct observables and involved non-linearities of the system. 

In this talk, we will discuss the characteristics and constraints of the reheating phase after inflation. 

The reheating generally consists of multiple episodes. We will describe the general characteristics of the initial non-perturbative phases with the results from lattice simulation. 

We will show how we can connect the reheating phase with CMB observables considering the perturbative decay of the inflation and the production of Gravitational waves during this phase.

We will conclude with a brief review of the information theory perspectives of the reheating phase.

148. May 11, Dr. Kazuki Enomoto (KAIST), Electroweak baryogenesis in the aligned two Higgs doublet model and its extension.  talk file.

Abstract:

Although the existence of asymmetry between matter (baryons) and anti-matter (anti-baryons) in the Universe has been known for a long time, its origin is still unknown. One attractive new physics scenario explaining baryon asymmetry is electroweak baryogenesis (EWBG) strongly relating to the nature of electroweak symmetry breaking, which will be thoroughly tested in various near future experiments. In this talk, we will discuss EWBG in two new physics models with extended Higgs sectors. The first model is an aligned two Higgs doublet model, where coupling constants of the 125 GeV Higgs boson coincide with those in the SM at tree level to satisfy the current LHC data. In this model, severe constraints from EDM measurements can be avoided by the destructive interference between CP-violating phases in the Higgs potential and the Yukawa interaction. The second model is an extension of the aligned two Higgs doublet model, where new Majorana fermions and scalar bosons are introduced, which are odd under a new unbroken Z_2 parity. In this model, tiny neutrino masses are generated by quantum effects of new particles, and the lightest Z_2 odd particle can be dark matter. I will introduce a benchmark scenario where neutrino mass, dark matter and baryon asymmetry of the Universe can simultaneously be explained with satisfying current experimental data.  Phenomenological predictions of these models in future experiments will also be discussed. 

This talk is based on JHEP01(2022)104, ibid.09(2022)121 and arXiv:2212.14786. 

147. April 27, Dr. Shu-Yu Ho (KIAS), Asymmetric SIMP dark matter.  talk file.

Abstract:

In this paper, we construct the first asymmetric strongly interacting massive particles (SIMP) dark matter (DM) model, where a new vector-like fermion and a new complex scalar both having nonzero chemical potentials can be asymmetric DM particles. After the spontaneous breaking of a U(1)D dark gauge symmetry, these two particles can have accidental Z4 charges making them stable. By adding one more complex scalar as a mediator between the SIMP DM, the relic density of DM is determined by 3 → 2 and two-loop induced 2 → 2 annihilations and dark asymmetry in this model. On the other hand, the SIMP DM can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the new gauge interaction. Interestingly, this model can have a bouncing effect on DM, whereby the DM number density rises after the chemical freeze-out of DM. With this effect, the prediction of the DM self-interacting cross section in this model can be consistent with astrophysical observations, and the ratio of the DM energy density to the baryonic matter energy density can be explained by primordial asymmetries. We also predict the DM-electron elastic scattering cross section that can be used to test this model in future projected experiments.

146. April 17 (Mon at 4pm, 102-106), Prof. Youngjoon Kwon (Yonsei), A Tale of Two-Leptons, department colloquium.

Abstract:

Leptons and quarks are constituent particles of matter in the Standard Model (SM).  Unlike quarks, leptons are not involved in the strong interaction.  As weak and electromagnetic interactions are much weaker than strong interaction, very precise SM predictions are made in the processes involving leptons, thus providing great testing ground of the SM.

In this talk, we present recent highlights from the Belle and Belle II experiments on B-meson decays to final states including a pair of leptons, discuss their implications and future prospects.  The Belle II is an $e^+ e^-$ collision experiment using the SuperKEKB collider at KEK, Japan and is the successor of the Belle experiment. We discuss, with $\ell^+ \nu$, the recent issues with lepton universality violations (LUV) in $R(D^{(*)}$ and intriguing tensions in $V_{cb}$, $V_{ub}$ measurements.  With $\ell^+ \ell^-$, we explore lepton flavor violation (LFV), LUV and other hints for new physics.  We also present searches for dark photons or other neutral gauge bosons that might decay to $\ell^+ \ell^-$.  Finally with $\nu \overline{\nu}$, we talk about invisible and semi-invisible $B$ and $D$ decays.  These invisible and semi-invisible decays also have implications for dark sector search.

145. April 6 (zoom), Dr. Nicholas Rodd (CERN), Positivity and the Topography of the SMEFT.  talk slides.  recorded talk.

Abstract: 

If the UV completion of the Standard Model is unitary, local, and causal, then a rigid structure emerges in the IR description of the physics provided by the SMEFT. In this talk I will outline how these restrictions emerge, describe how they apply to the SMEFT, and detail the experimental implications, including for existing collider searches. The constraints require the positivity of various SMEFT Wilson coefficients, but also require a deep connection between effects that conserve and violate flavor and CP in the theory. While most of the results I will present are for the SMEFT at dimension eight, I will also describe the steps and additional assumptions required to unravel its structure at dimension six.

144. March 18 & April 15 (Sat at 1pm), Prof. Sungwoo Hong (KAIST), Snail lecture I on generalized symmetries, Yonsei Univ, and Snail lecture II on generalized symmetries, KIAS.

143. March 15 (Wed at 4pm, 102-110), Prof. Viatcheslav Mukhanov (Munich & KIAS), How predictive are cosmological theories?  CAU HEP center seminar.  talk file.

Abstract: 

I will review the achievements in theoretical cosmology and CMB measurements during the last 40 years.

Seminars in fall 2022

142. Dec 22 (Thu at 6pm), Prof. Seong Chan Park (Yonsei Univ), Axion quality problem and its solution, Proca seminars, zoom.  talk file.

Abstract:

No global symmetry is exact in the presence of gravity. 

The global U(1) PQ symmetry for the QCD axion is explicitly broken by non-perturbative effects of gravity such as axionic wormholes. The gravitational violation of the PQ symmetry due to wormholes is large enough to invalidate the PQ mechanism, which is entitled as the axion quality problem. We suggest a novel solution to this quality problem based on non-minimal coupling in metric and Palatini formulation of gravity. 

141.  Dec 5 (Mon at 4:30pm, 102-106), Prof. Jeong Han Kim (Chungbuk National Univ), Searching for Imprints of New Particles in Cosmology, department colloquium.

Abstract:

Cosmological observations have a great potential to glean information about new physics beyond the Standard Model. The aim of the talk is to show how best to utilize cosmological data to search for signatures from some of the earliest phenomena in the universe over a vast range of scales. First, we explore the phenomenon of heavy particle productions during inflation which can lead to new signatures on the cosmic microwave background (CMB) and large-scale structure (LSS). Second, we explore the mirror twin Higgs models in which the entire particle content and symmetries of the Standard Model are replicated. This type of models not only leaves testable imprints on both CMB and LSS, but also alleviates the H0 and Sigma8 tensions simultaneously.

140.  Dec 5 (Mon at 2:30pm, 104-217), Prof. Jeong Han Kim (Chungbuk National Univ), Imprints of Heavy Inflationary Particles on the Large Scale Structure.  talk file.

Abstract:

The early universe had such an extremely high energy density that supermassive particles could have been produced. When heavy particles are pair produced during inflation via couplings to the inflaton, the particle mass generates a non-trivial curvature perturbation in position space. Even if the heavy particles no longer exist, the modified curvature perturbations are preserved before horizon re-entry and will generate locally-enhanced dark matter clumps or galaxy densities on the large-scale structure (LSS). We explore these signatures by studying the matter power spectrum and the abundance of massive halos, and discuss the discovery potential. We will go through the details of implementing the curvature perturbations in the N-body simulations with appropriately modifying initial conditions, and talk about several subtleties that we are currently coping with. It will allow us to properly include non-linear effects, and investigate a pairwise nature of signals which is difficult to study analytically. Finally, I will briefly introduce other interesting literatures that explore early universe models with using N-body simulations, and their general aspects.

139. Dec 1 (Thu at 1pm), Prof. Jisuke Kubo (Toyama Univ), Spontaneous Generation of Masses and Hierarchy Problem, zoom.  talk file.  recorded talk.

Abstract:

There are indications in particle physics as well as in cosmology that underlying theories are scale invariant. In scale invariant theories all the masses (or mass gaps) are spontaneously generated. Consequently, the hierarchy problem (or naturalness problem) looks different. Gravitational corrections become particularly important, if the Planck mass is spontaneously generated via a non-minimal coupling to the curvature scalar. I discuss this matter using realistic models.

138. Nov 24 (Thu at 6pm), Prof. Admir Greljo (Bern Univ), Model building and phenomenology with leptoquarks, zoom. talk file.  recorded talk.

Abstract: 

Leptoquarks - hypothetical particles motivated by quark-lepton unification - have recently been under the spotlight due to anomalies in flavor physics experiments. TeV-scale leptoquarks have a rich phenomenology both at intensity and energy frontiers. However, they also pose a model-building challenge since they typically violate accidental symmetries of the Standard Model, such as the baryon number. In this talk, I will discuss several aspects of leptoquark physics based on my recent work in this direction.

137. Nov 12 (Sat at 1pm), Prof. Min-Seok Seo (Korea University of Education), snail lecture: Quantum Field Theory.

136. Nov 9 (Wed at 3pm, 102-106), Prof. Jaewon Lee (Jungwon Univ), Ultralight dark matter and mysteries of galaxies, HEP Center seminar.

Abstract : 

Cold dark matter model (CDM) is very successful in explaining the observed universe at super-galactic scales. However, it 

encounters many problems at galactic scales such as the missing satellite problem and the cusp/core problem.

As an alternative to CDM, there is a growing interest in the fuzzy dark matter model. In this model dark matter is an ultralight scalar particle with mass m=O(10^−22)eV

having de Broglie wavelength about kpc, which help us solve the aforementioned small scale problems. The dark matter particles are in Bose-Einstein condensate and behave 

as coherent waves. We suggest that this model also may explain many other mysteries of galaxies.

135. Oct 27 (Thu at 6pm), Prof. Kiwoon Choi (IBS, CTPU), Distinguishing different axion models with precision low energy axion couplings, Proca seminars, zoom.

Abstract:

I discuss the low energy couplings of the three most typical type of axions, KSVZ-type, DFSZ-type and string-theoretic axions, while focusing on the possibility to discriminate those three type of axions from each other by the measurable couplings to the photons, nucleons, and electrons.

134. Oct 26 (Wed at 4pm), Dr. Jongkuk Kim (KIAS), Dark Matter physics with dark Higgs.

Abstract: 

In this talk, I consider scalar/fermion DM models with local dark U(1)_X gauge symmetry that is spontaneously broken into its Z_2 subgroup. In this model, dark Higgs boson plays a crucial role in DM phenomenology, not only for generation of dark photon mass, but also opening new channels for DM pair annihilations into the final states involving dark Higgs boson. Especially, in the case of U(1)_X =U(1)_{L_\mu-L_\tau} model, dark Higgs boson will dissect the strong correlation M_{Z′} ∼ 2M_{DM}, and much wider mass range is allowed for U(1)_X-charged complex scalar and Dirac fermion DM, still explaining the muon (g − 2). 

133. Oct 13 (Thu at 6pm), Prof. Chang Sub Shin (Chungnam National Univ), Dark Light Boson Emission from Supernovae, Proca seminars, zoom.  talk file.  talk video.

Abstract:

Supernovae are good laboratories to investigate new physics beyond the Standard Model which contains light dark particles. This is because the additional energy leakage sources by the dark particle emission can change the star evolution significantly. We re-examined the dark light boson (axion, dark gauge boson) emission from supernovae especially focusing on the effects of local contact interactions, pion-mediated Thomson-like process, decay of dark particle outside/inside the star, and medium effects on the effective charge of the nucleon. We obtained new constraints. In this talk, I will explain the physics behind the constraints.

132. Oct 8 (Sat at 1pm, 102-109), Dr. Suro Kim (KIAS), Snail lecture: Cosmological Collider Physics. 

Lecture 1 : Introduction and Inflation in a nutshell

ref : arXiv:0907.5424 [hep-th]

Lecture 2 : Cosmological collider program

ref : arXiv:0911.3380 [hep-th],  arXiv:1109.0292 [hep-th],  arXiv:1211.1624 [hep-th]

arXiv:1503.08043 [hep-th],  arXiv:1807.03098 [hep-th]

Lecture 3 : EFT approach and (beyond) positivity bound

ref: arXiv:0709.0293 [hep-th],  arXiv:hep-th/0602178,  arXiv:1906.11840 [hep-th]

131. Oct 6 (Thu at 1pm), Dr. Yusuke Yamada (Waseda Univ), QFT description of particle scattering during preheating, zoom. talk file.  video link. 

Abstract: 

In this talk, I will discuss scattering processes of particles that couple to classical backgrounds, such as a scalar field and gravity. Such processes are important in the context of preheating, where particles coupled to inflaton condensate are produced from vacuum non-perturbatively. I will briefly review properties of quantum field theory in time dependent backgrounds and how to describe scattering processes in such backgrounds. Then, I show a simple model of dressed particle scatterings, which exhibits non-trivial behavior due to the explicit breaking of time-translation invariance by backgrounds. 

Reference: H. Taya, Y. Yamada, arXiv:2207.03831

130.  Sept 29 (Thu at 1pm, 102-105), Dr. Neil Barrie (IBS, CTPU), Type II Seesaw leptogenesis.  talk file.

Abstract:

The Type II Seesaw Mechanism provides a minimal framework to explain the neutrino masses involving the introduction of a single triplet Higgs to the Standard Model. However, this simple extension was believed to be unable to successfully explain the observed baryon asymmetry of the universe through Leptogenesis. We have demonstrated that the triplet Higgs of the Type II Seesaw Mechanism alone can simultaneously generate the observed baryon asymmetry of the universe and the neutrino masses while playing a role in setting up Inflation. This is achievable with a triplet Higgs mass as low as 800 GeV, and predicts that the neutral component obtains a small vacuum expectation value v_∆< 10 keV. I will discuss the rich phenomenology of our model which can be tested by various terrestrial experiments as well as by astronomical observations. In particular, the successful parameter region may be probed at a future 100 TeV collider, upcoming lepton flavor violation experiments such as Mu3e, and neutrinoless double beta decay experiments.

129. Sept 22 (Thu at 1pm, 102-105), Dr. Adil Jueid (KIAS), Leptoquark solutions to the dark matter problem and the R_D anomalies.  talk file. 

Abstract: 

In this talk, I will discuss how a scalar leptoquark (LQ) singlet can simultaneously solve the $R_{D^{*}}$ anomalies and the dark matter problem. This will be exemplified in a minimal simplified LQ model where the SM is extended by two additional dark-sector particles: a Majorana fermion singlet, and a coloured Dirac fermion. We estimate the constraints from collider searches, direct detection experiments and the relic abundance. The correct relic density can not only arise from the standard freeze-out mechanism but also from the conversion-driven freeze-out mechanism. I discuss the rich phenomenological implications at colliders and point to holes that are left in the previous LHC searches.

Seminars in summer 2022

128.  August 18 (at 4pm, 104-212), Dr. Dibyendu Nanda (KIAS), Imprint of high-scale non-thermal leptogenesis at cosmic microwave background.  talk file.

Abstract: We discuss the imprint of high scale non-thermal leptogenesis on cosmic microwave background experiments from the measurement of spectral index (n_s) and tensor to scalar ratio (r) which is otherwise inaccessible to the conventional laboratory experiments. We argue that non-thermal production of baryon (lepton) asymmetry from tree level inflaton decay is sensitive to the reheating dynamics of the Universe after the end of inflation. Such dependence provides a detectable imprint on the n_s-r plane which is well constrained by the Planck experiment. We investigate two separate cases, (i) inflaton decays to radiation dominantly and (ii) inflaton does not decay to radiation at tree level. We obtain the corresponding estimates for n_s and r and find the latter case to be more predictive in view of recent Planck/BICEP data. The method presented here is generic and can be implemented to various kinds of single field inflationary models given the conditions for non-thermal leptogenesis is satisfied.

127. August 17 (at 2pm, 102-110), Prof. Gabriela Barenboim (Univ Valencia), NEUTRINOS :  WHERE WE ARE ? WHERE WE ARE HEADING TO ?  indico page.  talk file.

Abstract: I will review neutrino physics oscillations, the status of the results (standard and anomalous) and the prospects for the future, mainly in the oscillation program.

References:

Pilar's review for beginners,  https://arxiv.org/abs/1708.01046

G. Barenboim, lectures for CERN, https://inspirehep.net/literature/1820389

Advanced topics, https://arxiv.org/abs/2111.07586

BSM searches, https://inspirehep.net/literature/2055710

126. July 14 (at 4:00pm-5:30pm, 104-212), Prof. Michael Trott (Niels Bohr Institute), The Geometric SMEFT description of curved Higgs Field Space(s).  Indico link.  talk file.

Abstract: In recent years, the effective field theory approach to the Standard Model, the SMEFT, has been used to study LHC data with ever increasing theoretical precision and sophistication. However, the complexity of this theory lead to several barriers  to substantial theoretical progress. In particular, the explosion in the number of parameters in the SMEFT as a function of operator mass dimension, and the technical challenge or reformulating SM predictions consistently into the SMEFT were very serious problems. This called into question the possible success and value of the SMEFT physics program over the long term. I will discuss how these challenges have been overcome. The key point leading to this advance, is the understanding that the projection of curved scalar field spaces generated by the Higgs onto a naive flat field space understanding-- implicitly embedded into the usual SMEFT  Lagrangian, and approach -- was the root cause of many problems, technical challenges and confusions. Many outstanding issues have now been addressed and immediately overcome by reformulating the SMEFT noting its curved scalar field space(s) - in the Geometric SMEFT. Some examples of the benefits of this approach will be presented, and explained.

I will also emphasise that the lessons that have been learned are more general than the SMEFT. The defining nature of field redefinitions in EFT’s, and the invariance of observables under the same, means that field theories can be profitably and generally understood as fundamentally geometric in character in many cases.

125. June 24 (at 11am, 102-110), Mr. Jong-Hyun Yoon (Helsinki), Dark matter production during preheating.  talk file.

Abstract: We discuss in detail the primordial production of dark matter by a classical inflaton field after inflation. During preheating, the oscillation of the inflaton background with a large amplitude can lead to intense particle production for a short period of time. One may apply this idea to explain the current relic abundance of dark matter within the minimal extension of the Standard Model. Based on minimalism, we study different production mechanisms of dark matter with the simplest set of renormalizable interactions. We also find that Planck-suppressed operators can lead to efficient particle production and can alone account for all the dark matter in the Universe.

Seminars in spring 2022

124. June 2 (104-212), Prof. Myeonghun Park (Seoultech), Quantum information and high energy physics.  talk file.

Abstract: In this talk, I will explain how a quantum technology, advanced computing can be a guide to searches for new physics. Here I will focus on examples of quantum computings and quantum communications.

123. May 26 (102-109), Prof. Ki-Young Choi (Sungkyunkwan Univ), Dark matter halo in the neutrino background.  talk file.

Abstract: I will talk about the impact of the dark matter interaction with neutrinos

on the formation of dark matter halos. In our recent paper, arXiv 2204.01431, we found that

the interaction can make the dark matter halo cored, which can give constraints on the dark matter-

neutrino scattering cross-section for the non-relativistic neutrino.

122. May 11 (at 4pm), Dr. Yuto Minami (Osaka), LiteBIRD: A future satellite mission on CMB polarization. CAU HEP Center seminar. recorded talk.  talk file.

Abstract:

LiteBIRD, the Lite (Light) satellite for the study of $B$-mode polarization and Inflation from cosmic background Radiation Detection, is a next-generation satellite mission aiming to measure the polarization of the Cosmic Microwave Background (CMB) radiation at unprecedented all-sky sensitivity. The main scientific target of LiteBIRD is to search for a signal from cosmic inflation imprinted in the $B$-mode polarization of CMB. The measurements of LiteBIRD will also allow us to address other new physics beyond the standard models of particle physics and cosmology. To realize the scientific target, LiteBIRD will map the microwave sky for three years at Sun-Earth Largrangian point 2 (L2) with three telescopes which have 15 frequency bands from 34 to 448 GHz to achieve a total sensitivity of 2.2$\,\mu$K-arcmin, with typical angular resolution of 0.5$^\circ$ at 100 GHz. In this talk, I will introduce the LiteBIRD mission and details of its expected scientific outcomes.

121. April 28, Dr. Sebastian Zell (EPFL Laussanne), The Ambiguities of General Relativity: Implications for Inflation and Dark Matter. recorded talk.  talk file.

Abstract

General Relativity (GR) exists in different formulations. They are equivalent in pure gravity but  lead to distinct predictions once other fields are included. First, I will give an overview of various versions of GR and highlight metric-affine gravity, which encompasses the metric, Palatini and Einstein-Cartan formulations as special cases. Generically numerous free parameters arise when matter is coupled (non-minimally) to GR. This has important implications for inflationary scenarios driven by the Higgs field. Predictions are no longer unique but they agree with observations in large parts of parameter space. Finally, I will present a new mechanism for producing fermionic dark matter in the early Universe.

Based on:

M. Shaposhnikov, A. Shkerin, I. Timiryasov, S. Zell,

    Higgs inflation in Einstein-Cartan gravity, JCAP 02 (2021), arXiv:2007.14978;

    Einstein-Cartan Portal to Dark Matter, Phys. Rev. Lett. 126 (2021) 161301, arXiv:2008.11686.

G. Karananas, M. Shaposhnikov, A. Shkerin, S. Zell,

    Matter matters in Einstein-Cartan gravity, Phys. Rev. D 104 (2021) 064036, arXiv:2106.13811.

C. Rigouzzo, S. Zell, Coupling Metric-Affine Gravity to a Higgs-Like Scalar Field, arXiv:2204.03003. 

120. April 14, Prof. Ranjan Laha (Indian Institute of Science, Bangalore), Low-mass primordial black holes as the dark matter candidate. recorded talk.  talk file.

Abstract:

Primordial black holes (PBHs), possibly formed via gravitational collapse of large density perturbations in the very early universe, are one of the earliest proposed and viable dark matter (DM) candidates. Recent studies indicate that PBHs can make up a large or even entire fraction of the present day DM density for a wide range of masses. Ultralight PBHs in the mass range of 10^{15} - 10^{17} g, emit particles through Hawking radiation, and can be probed via observations of those emitted particles in various detectors. In this talk, I will discuss how the observations of the 511 keV gamma ray line and continuum gamma-rays set some of the most stringent exclusion limits on the DM fraction of ultralight PBHs. I will also demonstrate how measurements of low-energy photons from the Galactic Center by the imminent telescopes such as AMEGO can probe the DM fraction of PBHs into a completely unexplored mass window.

119. April 7, Dr. Wenyuan Ai (Kings College London), Particle production from oscillating scalar condensates. recorded talk. talk file.

Abstract: 

In this talk, I will discuss perturbative particle production from oscillating scalar backgrounds in a spatially flat Friedmann–Lemaître–Robertson–Walker universe using non-equilibrium quantum field theory. The latter naturally captures the thermal effects and backreaction effects.  For quasi-harmonic oscillations, we adopt the multi-scale analysis to obtain analytical approximate expressions for the self-consistent evolution of the scalar background and the energy density of the produced particles in terms of the retarded self-energy and retarded proper four-vertex function, whose imaginary parts characterize different condensate decay channels and lead to dissipation. At finite temperature, there are many new condensate decay channels that would be absent at zero temperature. These new channels could play an important role in ensuring a complete reheating.

118. March 24,  Prof. Matthew Mccullough (CERN),  Gegenbauer Goldstones. recorded talk.  talk file.

Abstract:  I will show that, for an approximate SO(N) global symmetry spontaneously broken by the fundamental representation there is an infinite class of radiatively stable pseudo-Nambu-Goldstone (pNGB) potentials which are Gegenbauer polynomials.  This observation will be used to construct new classes of pNGB Higgs models, “Gegenbauer Higgs” and “Gegenbauer’s Twin”, which are significantly less fine-tuned than previously considered pNGB Higgs scenarios.  In particular, the latter requires no fine-tuning to be rendered consistent with LHC measurements and exhibits the smoking gun signal of large Higgs self-coupling modifications which may be discoverable at the HL-LHC.

Seminars in fall 2021

117. December 17 (at 11:30am), Dr. Sang Hui Im (IBS-CTPU), Prospect for the discovery of axions and probing their microscopic origins, CAU HEP Center seminar. recorded talk.  talk file.

Abstract:

In this talk, I will review the status and prospect for directly detecting axions in the standard parameter space, namely detection of the QCD axion, axion dark matter from the misalignment production mechanism, and string-theoretically originated axions. I will also discuss the possibility to experimentally determine the microscopic origins of axions by low energy precision measurements.

116. December 13 (at 4:30pm), Prof. Seung Joon Lee (Korea Univ), 입자물리학으로 바라본 우주 존재 이유와 새로운 물리학 탐색, department colloquium.

Abstract:

본 강연에서는 "우주는 어떻게 시작했으며 무엇으로 만들어졌는가? 왜 우리 우주의 작동 원리는 무엇이며, 왜 우리는 존재하는가?"라는 질문들을 현대 입자물리학이 어떻게 풀어나가고 있는지 소개할 것이다. 거대강입자 가속기(LHC)와 그 너머 새로운 실험들이 얼마나 흥미진진한 일인지를 이론적인 고찰을 통해 살펴볼 것이며, 우리 우주를 구성하고 있는 물질의 대략 80%를 차지하고 있는 우주 암흑물질에 대해서도 살펴볼 것이다.

115. November 24 (at 4pm), Dr. Shreya Banerjee (Friedrich Alexander University), online, Observational Constraints on Superfluid Dark Matter Models. recorded talk.  talk file. 

Abstract:

The Lambda-Cold Dark Matter (LCDM) model agrees with most of the cosmological observations, but has some hindrances from observed data at smaller scales such as galaxies. Berezhiani and Khoury proposed a new theory involving interacting superfluid dark matter with three model parameters, which explains galactic dynamics with great accuracy. In my talk,  I shall discuss the cosmological behaviour of this model in the linear regime of cosmological perturbations. In particular, I shall obtain new bounds for the model parameters which are significantly stronger than previously found. These new constraints come from the fact that structures within the superfluid dark matter framework grow quicker than in LCDM, and quite rapidly when the DM-baryon interactions are strong. 

In my talk, I shall also explain how we obtain further new bounds using the present constraint on the gravitational wave (GW) propagation speed from BNS GW170817. The speed of GW has been shown to depend upon the refractive index of the medium, which in turn, depends on the dark matter model parameters through the density profile of the  galactic halo. Through our analysis, we find new tighter bounds on the parameter space for the superfluid model.

114. November 17 (at 4pm), Prof. Takashi Toma (Kanazawa Univ), online, Direct detection of pseudo-Nambu-Goldstone dark matter with light mediator. recorded talk.  talk file.

Abstract: 

It has been found that a pseudo-Nambu-Goldstone boson dark matter

suppresses the amplitude for elastic scattering with nuclei in

non-relativistic limit, and thus can naturally evade the strong

constraint of dark matter direct detection experiments. In this talk, we

show that non-zero elastic scattering cross section can be induced if

the mediator mass is as small as momentum transfer. The predicted recoil

energy spectrum can differ from that for usual thermal dark matter.

Together with the relevant constraints such as thermal relic abundance,

indirect detection and Higgs decays, we investigate the detectability

through the current and future dark matter direct detection experiments.

113. October 27 (at 4pm), Prof. Ligong Bian (Chongqing Univ, China), online, Probing new physics with gravitational waves and magnetic fields observations. talk file.  recorded talk.

Abstract: 

In this talk, I will share with you our progresses on the study of gravitational waves and magnetic fields. 

We found that both the two can be complementary to search for new physics beyond the standard model. 

112. October 14 (at 11am), Dr. Junichiro Kawamura (IBS-CTPU), online, Complete vectorlike fourth family and new U(1)' for muon anomalies. talk file.  recorded talk.

Abstract: 

We consider the Standard Model (SM) with the addition of a U(1)′ gauge symmetry and a complete fourth family of quarks and leptons which are vectorlike with respect to the full SU(3)C×SU(2)L×U(1)Y×U(1)′ gauge symmetry. The model provides a unified explanation of experimental anomalies in (g-2)μ as well as b→sℓ+ℓ- decays. We find good fits to the deviations from the SM, while at the same time fitting all other SM observables. The model includes a new Z′ gauge boson, a U(1)′-breaking scalar, and vectorlike leptons all with mass of order a few hundred giga-electron-volts. It is consistent with all currently released high energy experimental data; however, it appears imminently testable with well-designed future searches. Also, we propose a novel possibility to detect a very distinctive signal with more than four muons originating from pair-produced vector-like leptons decaying to a muon-philic Z′ boson. This talk is based on 1906.11297, 1911.11075 and 2104.04461.

111. October 7 (at 11am), Dr. Kunio Kaneta (KIAS), online, Dark Matter Production During Reheating. talk file. recorded talk.

Abstract: 

Among the various types of dark matter candidates, the Feebly Interacting Massive Particle (FIMP) has a particularly interesting feature characterized by feeble couplings to the Standard Model particles. Such feeble interactions still allow for the FIMP dark matter to be produced by, for instance, annihilations of the Standard Model particles, whereas the backward reactions rarely occur, preventing the dark matter candidate from reaching thermal equilibrium. This non-thermal nature of FIMP implies that its relic abundance is sometimes sensitive to the epoch of the reheating and hence the inflaton dynamics (including preheating). To illustrate this point, I will discuss some simple examples of dark matter scenarios. Then, I will extend the argument to more generic cases where inflaton undergoes an anharmonic oscillation during reheating and emphasize that the dark matter production during this period significantly alters the prediction of the dark matter relic abundance. 

110. September 29 (at 4pm), Dr. Tevong You (CERN and Univ of Cambridge), online, Self-Organised Localisation. talk file. recorded talk. 

Abstract: 

We describe a new phenomenon in quantum cosmology: self-organised localisation. When the fundamental parameters of a theory are functions of a scalar field subject to large fluctuations during inflation, quantum phase transitions can act as dynamical attractors. As a result, the theory parameters are probabilistically localised around the critical value and the Universe finds itself at the edge of a phase transition. We illustrate how self-organised localisation could account for the observed near-criticality of the Higgs self-coupling, the naturalness of the Higgs mass, or the smallness of the cosmological constant.

109. September 15 (at 4pm), Dr. Liliana Kersten (Bergen Univ), online, Swampland de Sitter Conjectures in No-Scale Supergravity Models. talk file.  recorded talk.

Abstract:

Motivated by the Swampland Program, which addresses the difficulty of realizing de Sitter solutions in string compactifications, we  study a toy de Sitter No-Scale Supergravity model and show that for particular choices of parameters it can be consistent with the Refined de Sitter Conjecture and the Trans-Planckian  Censorship Conjecture. Then we add rolling dynamics and show that  the theory can become stable along the imaginary direction, where it would otherwise be unstable.  We then generalize to the case of multi-field rolling and de Sitter fields,  finding  the parameter space where they can be compatible with the Refined de Sitter Conjecture. The modified models with rolling fields can be used to construct Quintessence models to accommodate the accelerating expansion of the Universe.

Ref. https://arxiv.org/abs/2105.14501

Seminars in spring 2021

108. June 30 (ar 2pm), Dr. Takahiro Terada (IBS-CTPU), online, Minimal Supergravity Inflation and (Not) Slow Gravitino. talk file.  recorded talk.

Abstract:

In the inflationary model building in supergravity, it is desirable to

strongly stabilize fields other than the inflaton so that they are

heavy enough to decouple.  In the "Minimal Supergravity Inflation"

model, supersymmetry is realized non-linearly and various fields in

the inflation sector are decoupled due to constraints; the only

remaining degrees of freedom are the (real) inflaton, graviton, and

massive gravitino.  In this talk, we first review an issue of

anomalous or catastrophic gravitino production due to the nontrivial

propagation speed of gravitino in this model, which would lead to the

production of arbitrarily high-energy gravitinos.  Then, we utilize a

recently proposed constrained superfield to propose an alternative

realization of the Minimal Supergravity Inflation scenario.  Although

the model is plagued by the gravitino problem as in generic

supergravity models, we show that the proposed model is free from the

catastrophic production issue.

107. June 2-4 (at 3pm-6pm), Dr. Kai Schmitz (CERN), online, Lectures on Gravitational Waves.  recorded talks: Lect 1, Lect 2, Lect 3.

Abstract:

The field of gravitational-wave astronomy has seen rapid and impressive progress since the first direct detection of gravitational waves in 2015; and yet the exciting journey has just begun. In the coming decades, gravitational waves will continue to expand their role as an indispensable tool for astrophysics and cosmology and advance to a primary probe of fundamental physics in the 21st century. In light of these prospects, this lecture series will highlight some of the exciting new physics scenarios that we might be able to discover in the gravitational-wave sky, with a special focus on gravitational waves from the early Universe. After a general introduction to gravitational waves in general relativity (Lecture I) and an overview of ongoing and future gravitational-wave experiments and observations (Lecture II), we will turn to particle cosmology and possible cosmological sources of stochastic gravitational-wave backgrounds, in particular, primordial gravitational waves from cosmic inflation (Lecture III), first-order phase transitions (Lecture IV), and cosmic defects (Lecture V). To conclude, we will discuss the recently announced NANOGrav signal and its possible interpretations and give an outlook onto the future of the field (Lecture VI).

106. May 26 (at 3pm), Prof. Eric Kuflik (Hebrew Univ ), online, Super Heavy Thermal Dark Matter. talk file.  recorded talk.

Abstract:

The WIMP paradigm has been a guide towards the properties of DM for

many years. Its abundance today is determined due to its interactions

with the Standard Model, and since it is a thermal dark matter

candidate, its abundance is insensitive to initial conditions. It has

long been thought that a dark matter candidate with these properties

has its mass bounded above by around 100 TeV, according to the

so-called unitary bound. I will show that a thermal dark matter

candidate, much like the WIMP, can have mass well beyond this, all the

way up to the Planck scale. I will present three different freezeout

mechanisms--zombies, a chain, and squeeze out--that all predict dark

matter particles well above 100 TeV.

105. May 20 (at 4pm), Prof. Yann Mambrini (Universite Paris-Saclay), online, From Hot Universe to dark Matter. recorded talk.

Abstract:

In this seminar, I propose to discuss the condition of production of Dark Matter in the early phase of the Universe, i.e. the reheating period. I will especially show how a precise determination of the evolution of the temperature is important, especially in UV models of the type supergravity, Z' or spin-2 portal. We will also show the influence of the radiative inflaton decay in the process.

104. May 12 (at 4pm), Prof. Veronica Sanz (Univ of Sussex and Univ of Valencia), online, Symmetry meets AI.  recorded talk.

Abstract:

Artificial Intelligence, especially its branch of Deep Learning, is a disruptive technology whose implications we are just starting to fathom. Due to its impressive successes, AI is somehow regarded as a magical blackbox, able to surpass human ability in an inexplicable way. We, theoretical physicists, do not like blackboxes and enjoy breaking things. So in this talk I am going to start breaking one of these boxes and watch an AI learn the presence of symmetries when no information on symmetry was provided. It isn't magic, but it is the AI doing its best to perform a task and finding the smartest route to succes. Once we have learned the inner workings of the AI, we are going to use it to develop an algorithm which inspects artistic works and assigns a degree of symmetry to them. This is one step towards a much broader aim of understanding the inner workings of AI, like developing new ways of learning or controlling for the presence of unethical biases.

103. May 10 (at 5pm), Prof. Nakwoo Kim (Kyunghee Univ), online, Black hole and Quantum Mechanics : Theoretical Understanding, department colloquium. talk file.

Abstract:

블랙홀은 아인슈타인 일반상대론의 자연스러운 예측이면서 우주에 실제로 무수히 존재한다. 무한대의 시간지연이 일어나는 시공의 지평선과 시공간 특이점을 내포하고 있어 여러 관측 결과에도 불구하고 이론적인 이해는 아직 현재진행형이다. 이 발표에서는 블랙홀의 기본적 성질을 설명하고 끈이론 등 최근의 이론적 발전에 기반한 블랙홀 수수께끼의 해결 방식을 소개한다.

102. April 16 (at 11:30am), Dr. Seung Joo Lee (IBS-CTPU),  online, Quantum Gravity and the Universe, CAU HEP Center seminar. talk file.

Abstract:

Quantum Field Theory is a modern framework of theoretical physics to describe the quantum dynamics of particles. However, any models of Quantum Field Theory, once coupled to gravity, necessarily break down at very high energies. This talk will address String Theory as a powerful quantum framework for both particles and gravity. While String Theory is originally defined in ten spacetime dimensions, physics in 3+1 dimensions may effectively arise at low energies via compactification, i.e., if the extra spatial dimensions are compact and small. Such effective physics is associated, via precise rules of compactification, to the geometry of a compact space satisfying the string equations of motion. We will first introduce the natural quest for constructing string-theoretical models for the Universe in terms of appropriate compactification geometries, and will discuss challenges as well as the state of the art. Next, switching gears, we will stress that the set of all consistent models of string theory form a perfect arena to study mysterious quantum nature of gravity. Upon motivating recent research activities in the community along this line, we will propose how constraints of quantum gravity are universally realized in string geometry.

101. March 25 (at 11:00am), Prof. Kwang Sik Jeong (PNU), online, Axion-driven hybrid inflation over a barrier. talk file.  recorded talk.

Abstract: We present a novel cosmological scenario that describes both inflation and dark matter. A concrete realization of our scenario is given based on a well-established particle physics model, where an axion-like field drives inflation until a potential barrier, which keeps a waterfall field at the origin, disappears to trigger a waterfall transition. Such a barrier makes the inflaton potential much flatter, improving significantly the naturalness and viability of the otherwise problematic setup adopted previously. The observed spectrum of the cosmic microwave background indicates that the inflationary Hubble scale, which is allowed to span a wide range, uniquely fixes the inflaton mass and decay constant. This raises an intriguing possibility of probing inflation via experimental searches for axion-like particles. Further, our model involves dark matter candidates including the inflaton itself. Also, for a complex waterfall field, we can determine cosmologically the Peccei-Quinn scale associated with the strong CP problem. 

Ref: https://arxiv.org/abs/2101.11173

Seminars in winter 2021

100. Feb 26 (at 2pm), Dr. Shuntaro Aoki (Waseda Univ), online, Disentangling mass spectra of multiple fields in cosmological collider. talk file.

Abstract:

It has been recently claimed that cosmological higher order correlation functions of the primordial curvature perturbations play important roles not only for restricting inflation models, but for exploring a new massive particle (isocurvaton) with mass up to the Hubble scale H. This approach known as the cosmological collider has attracted much attention so far, because the energy scale H is typically much higher than that of terrestrial experiments. In this talk, I discuss effects of multiple scalar fields (scalar isocurvatons) with the Hubble scale masses on the inflationary bispectrum in the squeezed limit, particularly paying attention to the question how to disentangle mass spectra of such fields. A characteristic feature associated with nearly degenerate masses in the oscillating part of the bispectrum is investigated in detail.

Ref: https://arxiv.org/abs/2012.13667

ZOOM link:  https://cau.zoom.us/j/4611373590

99. Jan 21, 22 (10am-4pm): Prof. Hyun Min Lee (Cosmology), Dr. Bin Zhu (Direct detection), and Dr. Yang-Hwan Ahn (Axion), online, lectures at CAU Winter School on Particle Physics and Cosmology.

98. Jan 14, 15 (10am-4pm): Prof. Hyun Min Lee (SM), Prof. Myeonghun Park (Machine Learning), online, lectures at CAU Winter School on Particle Physics and Cosmology.

Seminars in fall 2020

97. Dec 18 (at 2pm), Prof. Joern Kersten (Bergen Univ, Norway), online, Neutrino Physics: Theory and Latest Experimental News. talk file.

Abstract:

I will review the theory of neutrino oscillations, including some details regarding the equal-momentum assumption and the wave packet formalism that are usually omitted.  Afterwards I will discuss current experiments and what we have learned from them, before concluding with an outlook on what news we can expect in the future.

A few papers and book on theoretical aspects:

Giunti & Kim, arXiv:hep-ph/0011074

Beuthe, arXiv:hep-ph/0109119

Kersten & Smirnov, arXiv:1512.09068

Akhmedov, arXiv:0706.1216

Giunti & Kim, Fundamentals of Neutrino Physics and Astrophysics.

Recent experimental results:

Esteban et al., arXiv:2007.14792, with updates at http://www.nu-fit.org/.

Fairly recent reviews of sterile neutrinos:

Giunti et al., arXiv:1906.01739

Diaz et al., arXiv:1906.00045

ZOOM link: https://cau.zoom.us/j/89402085027

96. Dec 10 (at 10am), Dr. Yu-Dai Tsai (Fermilab), online, New Models, Experiments, and Neutrino Searches at the High-Energy Intensity Frontier – Resonant SIDM, FORMOSA, LongQuest, and Forward Neutrino Campus. recorded talk.

Abstract:

In this talk, I will give a general overview of experimental facilities with both high energies and high intensities, and how they can help explore dark matter models, complementary to astrophysical and cosmological searches. I will then talk about my new experimental proposals (FORMOSA, LongQuest, & Forward-DUNE) utilizing these facilities to study dark-sector models, including millicharged particles and portals to the dark sector, and neutrino physics. 

I will then discuss the possibility of constructing a TeV "Forward Neutrino Campus" at the LHC forward physics region, using Forward Proto-DUNE and FORMOSA as examples. Forward Proto-DUNE can help fill in the gap between low-energy and high-energy neutrino cross-section measurements, and FORMOSA can study tau neutrino electric dipole moment.

Finally, I will discuss a new model, Resonant Self-Interacting Dark Meson, and tie it to the accelerator searches at the high energy-intensity frontier. I will also discuss how observations on the galactic scales can help distinguish different models.

This talk is based on arXiv:2008.08608, arXiv:1908.07525, arXiv:2010.07941, arXiv:1812.03998, and ongoing works.

ZOOM link: https://cau.zoom.us/j/89402085027

95. Dec 7 (at 4:30pm), Prof. Jihun Kim (SNU), Solving the Mysteries of Supermassive Black Holes in the Era of High-resolution Numerical Simulations, department colloquium.

 Abstract:

Supermassive black holes (SMBHs) lurking at the centers of most galaxies are intriguing objects that are yet to be fully understood.  When experimenting with stars, galaxies, or black holes is humanly impossible, numerical simulations are often the only means to test our theory of Universe's structure formation.  Fortunately, the community of numerical structure formation has benefited greatly from the ever-improving computing technology over the past decades.  In this talk, I will discuss the new possibilities in the upcoming era of high-resolution numerical simulations, and highlight efforts to overcome the accompanying challenges.  As one example, I will describe a state-of-the-art simulation of a SMBH-host galaxy (quasar) in the early Universe, and demonstrate that previously undiscussed types of interplay between galactic components may hold important clues about the growth of SMBHs. 

ZOOM link: https://cau.zoom.us/j/4611373590

94. Dec 3 (at 5pm), Dr. Chang Sub Shin (IBS CTPU), online, Exploring the Universe with Dark Light Scalars. talk file.

Abstract:

We study the cosmology of a dark sector consisting of (ultra) light scalars. Since the scalar mass is radiatively unstable, a proper explanation is required to make it much smaller than the UV scale. The scalar can be identified as a pseudo-Goldstone boson, whose shift symmetry is explicitly broken by non-perturbative corrections, like the axion. Alternatively, it can be identified as a composite particle like the glueball, whose mass is limited by the confinement scale of the theory. In both cases, the scalar can be naturally light, but interaction behavior is quite different. The lighter the axion (glueball), the weaker (stronger) the interaction is. We consider the dark axion whose shift symmetry is anomalously broken by the hidden non-abelian gauge symmetry. After the confinement of the gauge group, the dark axion and the dark glueball get masses and both form multi-component dark matter. We carefully consider the effects of energy flow from the dark gluons to the dark axions and derive the full equations of motion for the background and the perturbed variables. The effect of the dark axion-dark gluon coupling on the evolution of the entropy and the isocurvature perturbations is also clarified. Finally, we discuss the gravo-thermal collapse of the glueball subcomponent dark matter after the halos form, in order to explore the potential to contribute to the formation of seeds for the supermassive black holes observed at high redshifts. With simplified assumptions, the glueball subcomponent dark matter with the mass of O(0.01−1MeV), and the axion dark matter with the GUT scale decay constant (the mass of O(10^-14 to 10−18)eV) can provide the hint on the origin of the supermassive black holes at high redshifts.

ZOOM link: https://cau.zoom.us/j/4611373590

93. Nov 12 (at 10am), Dr. Kimiko Yamashita (IHEP), online, Higgs Inflation, Vacuum Stability, and Leptogenesis. talk file.

 Abstract:

We consider the introduction of a complex scalar field carrying a global lepton number charge to the Standard Model and the Higgs inflation framework. The conditions are investigated under which this model can simultaneously ensure Higgs vacuum stability up to the Planck scale, successful inflation, non-thermal Leptogenesis via the pendulum mechanism, and light neutrino masses. These can be simultaneously achieved when the scalar lepton is minimally coupled to gravity, that is, when standard Higgs inflation and reheating proceed without the interference of the additional scalar degrees of freedom. If the scalar lepton also has a non-minimal coupling to gravity, a multi-field inflation scenario is induced, with interesting interplay between the successful inflation constraints and those from vacuum stability and Leptogenesis. The parameter region that can simultaneously achieve the above goals is explored.

Reference: JHEP 08 (2020) 072. Also see Phys. Lett. B 785, 184-190 (2018) and Mod. Phys. Lett. A 33, no. 17, 1850097 (2018).

ZOOM link: https://cau.zoom.us/j/84945057375

92. Oct 29 (at 5pm), Dr. Javier Rubio (Instituto Superior Técnico, Lisbon), online, Higgs inflation and the nature of gravity. talk file.

 Abstract:

Higgs inflation is an appealing inflationary model based on the inclusion of a non-minimal coupling between the Higgs field and gravity. Although the scenario was initially formulated as a metric theory in which the connection determining the Ricci scalar was identified with the Levi-Civita connection, this need not be the case. In particular, one could consider a Palatini formulation of gravity in which the metric and the connection are taken to be independent geometrodynamical variables. In this talk, I will discuss the pros and cons of these two alternative scenarios and their implications for the large hierarchy between the electroweak and the Planck scale.

ZOOM link: https://cau.zoom.us/j/89645635002

91. Oct 15 (at 5pm), Dr. Bibhushan Shakya (CERN), online, Light Extended Neutrino Sectors: Foundations and Phenomenology.  talk file.

 Abstract: 

Beyond the Standard Model extensions of the neutrino sector are an active area of research, primarily in the context of explaining neutrino masses, dark matter, and various anomalies. In this talk, we will discuss theoretical frameworks for light extended neutrino sectors - consisting of sub-GeV sterile neutrinos charged under exotic symmetries - and their diverse phenomenology in terms of dark matter possibilities, cosmology, and direct searches.

ZOOM link: https://cau.zoom.us/j/86274484829

90. Oct 8 (at 5pm), Dr. Yohei Ema (DESY), online, Higgs Inflation, Unitarity, and Emergence of Scalaron.  talk file.

 Abstract:

The Higgs inflation introduces a large non-minimal coupling between the Ricci scalar and Higgs that causes tree-level unitarity violation well below the Planck scale. After reviewing the unitarity issue during and after inflation, we show that the unitarity can be restored by summing over vacuum polarization-type diagrams that is justified in the large-N limit. The scattering amplitude develops a pole after the resummation, which we identify as the scalar component of the metric, or the scalaron. We also show that this phenomenon can be understood in the language of the non-linear sigma model (NLSM), with the scalaron identified as the sigma-meson that linearizes the NLSM.

ZOOM link: https://cau.zoom.us/j/89336852278

89. Sept 28 (at 4:30pm), Prof. Hyun Min Lee (CAU), Peeking into the Dark World, department colloquium. 

Abstract:

미시의 아원자 세계와 거대한 우주를 동시에 이해하려는 인간의 노력을 입자물리의 관점에서 기술한다. 표준모형의 힉스 입자를 넘어서서 새로운 기본입자를 도입하려는 이론적인 동기와 실험을 설명하고, 암흑 물질을 통해서 새로운 물리를 발견하려는 최신 연구 동향을 살펴보고자 한다.

We describe the human efforts to understand the microscopic world at subatomic level and the macroscopic world at cosmological scale. We explain theoretical motivations and experimental searches for going beyond the Higgs boson in the Standard Model and introduce the current research efforts to probe new physics through dark matter.

Seminars in fall 2019 - summer 2020

No seminar due to Sabbatical leave.

Seminars in summer 2019

88. July 3, 5 (at 11am) and July 8-10 (at 10:30am and 1pm), Prof. Hyun Min Lee (CAU) & Prof. Motoi Endo (KEK), Supersymmetry and new physics, Special lectures in CAU summer semester.

Seminars in spring 2019

87. May 30 (at 4pm), Dr. Wen Yin (KAIST), ALP inflation and inflaton hunt on the earth

Abstract:

I discuss hilltop inflation models where an axion-like particle (ALP) plays the role of the inflaton. We find that, for a broad class of potentials, the decay constant and the mass at the potential minimum satisfy the relation,

m\sim 10^{-6}f, to explain the CMB normalization. The ALP is necessarily coupled to the standard model particles for successful reheating. The ALP with the above relation can be searched at beam dump experiments, e.g., the SHiP experiment, if the inflation scale is sufficiently low. In this case, the ALP decays through the interactions that led to the reheating of the Universe. In other words, the Big Bang may be probed at ground-based experiments.

I also show that in another class of model, the inflaton can be the dark matter when the inflation scale is low enough with successful reheating. In the case, inflaton can be hunted in the IAXO experiment.

86. May 29 (at 4pm, 102-306), Prof. Ioannis Papadimitriou (KIAS), Supersymmetry anomalies

Abstract:

The Wess-Zumino consistency conditions for supersymmetric quantum field theories with an anomalous flavor or R-symmetry imply the existence of a supersymmetry anomaly, i.e. a non vanishing divergence for the supercurrent in the presence of fermionic sources for the flavor or current multiplets. I will discuss how this anomaly affects the supersymmetric partition function on backgrounds admitting rigid supersymmetry and outline other implications.

85. May 22 (at 4pm, 102-110), Dr. Kimiko Yamashita (National Tsing Hua University, Taiwan), Pendulum Leptogenesis

Abstract:

We propose a new baryogenesis scenario, which occurs during reheating after inflation.  

During reheating, the oscillation of the inflaton field breaks thermal equilibrium, providing one of the necessary conditions for baryogenesis. 

The inflaton field is assumed to couple to a complex scalar field which carries baryon number, whose self coupling breaks B, C and CP, providing 

the remaining two conditions for baryogenesis.  The dynamics of our scenario utilizes the so-called “ratchet mechanism” found in models of biological molecular motors.  

There, the driving force of the ratchet movement (of molecular motors) usually comes from the oscillatory change of temperature in the non-equilibrium state. 

In the present scenario this driving force is provided by the oscillation of the inflaton field.  

Baryon number is generated by the phase of the complex scalar field being driven in a preferred direction due to 

the oscillatory energy provided by the inflaton and the “ratchet” of the self-coupling potential. 

Our model of Baryogenesis dynamics is the same as that for a forced pendulum with many rotations. 

We apply this scenario to Leptogenesis and simultaneously provide an origin for neutrino masses via the seesaw mechanism.

References:

Mod. Phys. Lett. A 33, no. 17, 1850097 (2018) (arXiv: 1610.03268)

Phys. Lett. B 785, 184 (2018) (arXiv: 1805.04826)

84. May 15 (at 4pm, 102-805), Mr. Farid Pasha (Wolfram Research), Introduction to Mathematica

* Introduction to Mathematica: Getting started, Manipulate, Teaching Resources, Demonstrations project, Accessing Wolfram|Alpha curated data, Documentation center.

* Symbolic Computation: Computation with symbolic expressions, including polynomial operations, solving equations and functions from calculus.

* Numerical Computation: Fitting data, interpolation, integration, solving equations, differential equations, linear systems, and working with large arrays.

* Visualization and Graphics: Two- and three-dimensional plotting, plotting data, and creating dynamic and interactive graphics

* Special areas of interest: Machine Learning, Neural nets, Data Analysis, Enhanced image processing, visualizations, Statistical analysis, Wavelets and CUDA

83. April 4 (at 4pm), Dr. Ke-Pan Xie (SNU), Broad composite resonances and their signals at the LHC

Abstract: The existence of the $SU(2)_L$ triplet composite spin-1 resonances $\rho^{\pm,0}$ is a universal prediction of the strongly interacting new physics models addressing the naturalness problem. However, such resonances have never been found in the di-boson final states (i.e. $W^\pm Z/W^\pm h$, $W^+W^-/Zh$), which are expected to be the dominant decay channels of the $\rho$s. In this work we propose a new scenario that the $\rho$-resonances might be broad and mainly decay to the third generation quarks, in which the left-handed quark doublet $q_L = (t_L, b_L)$ is fully composite. In this case, The $t\bar{t}$ resonance search channel is comparable in sensitivity to the di-lepton channel. We also discuss how to use deep learning to improve the efficiency in the search for such a broad resonance.

82. March 30 (at 1:30pm), Prof. Keun Young Kim (GIST), AdS/CFT for phenomenologists (APCTP FRP), Science hall B102 at Yonsei University.

Abstract:

An esoteric word, "AdS/CFT" in the title just stands for a certain duality between quantum theory and gravity theory. Depending on the context, it may be called the AdS(Anti-de Sitter Space)/CFT(Conformal Field Theory) correspondence, gauge/gravity duality, or holographic principle(method). This lecture focuses on phenomenological aspects of "AdS/CFT". In particular, the main theme is to propose (not prove) how to describe strongly correlated quantum systems in terms of classical gravity theories. For example, some properties of quark-gluon plasma and strange metal (non-Fermi liquid) will be discussed. These belong to the research fields called AdS/QCD(Quantum Chromodynamics) and AdS/CMT(Condensed Matter Theory), which will not sound esoteric by now, hopefully.

13:30-14:30 Gravity-Field theory Dictionary

14:45-16:15 Holographic Thermodynamics: Thermodynamic variables, phase transition etc.

16:30-18:00 Holographic Transport: shear viscosity, conductivity etc.

References:

Holographic Quantum Matter, Sean A. Hartnoll et al. (https://arxiv.org/abs/1612.07324)

Gauge/String Duality, Hot QCD and Heavy Ion Collisions, Jorge Casalderrey-Solana et al. (https://arxiv.org/abs/1101.0618)

81. March 11 (at 4:30pm, 102-106), Prof. Seong Chan Park, 21세기 입자물리학자들의 고민, department colloquium.

Abstract:

표준입자물리학 모형은 현재 인류가 도달한 가장 정확한 물리이론입니다. 

하지만 입자물리학자들은 표준모형의 성공에 안주하지 않고, 그 너머의 새로운 물리학을 찾기 위해 새로운 발걸음을 이어가고 있습니다.

이번 강연에서는 어떤 이론적, 실험적 노력들이 진행되고 있는지 그 고민을 공유하려 합니다.

Seminars in winter 2019

80. Feb 21 (at 4pm), Dr. Seokhoon Yun, Photon-ALP-dark photon oscillation and its phenomenological implications

Abstract : The physics of conversion of the photon to ALP (axion-like particle) induced by the conventional ALP coupling to the photon in the presence of the background magnetic field has been well studied. This interesting phenomenological aspect can be used to probe a signal of the new physics beyond the standard model. As an example, the EDGES anomaly of the 21cm signal and the spectral irregularities of the Fermi-LAT data can be explained by the conversion of the photon to ALP. However, the corresponding ALP mass and coupling are in a severe tension with the present constraints. With this motivations, I will talk about our recent work on the photon-ALP-dark photon oscillation as an alternative possibility to resolve such difficulties.

Reference : 1806.09508

Seminars in fall 2018

79. Dec 3 (at 3pm), Prof. Matthew Buckley (Rutgers Univ), Gravitational probes of dark matter physics, The 2nd Korea Meeting.

Abstract: Gravity provides both the evidence for dark matter and all of our present knowledge about its properties. By understanding the detailed structure of gravitationally bound objects in our Universe, we can probe the particle physics of dark matter in a way that is completely orthogonal to the Earth-based high-energy physics searches for dark matter. Such efforts will require close collaboration between astronomers and particle physicists, but have a great deal of potential in the near future. I will describe a useful parameter space to make connections between the two fields, and areas of potential advance.

The 1st Korea meeting.

78. Nov 29 (at 4:30pm),  Dr. Ke-Fan Xie (SNU), Searching for the resonances of the Minimal Composite Higgs Model at the LHC, postponed to next semester.

Abstract: The composite Higgs models provide a natural solution to the Standard Model gauge hierarchy problem. In such models, the Higgs boson is a composite particle instead of an elementary one; it is identified as the pseudo Nambu-Goldstone boson of some strong dynamical new physics at scale O(TeV). In this talk, I will first review the motivations of the composite Higgs models, and then discuss their main phenomenological features, i.e. the existence of new vector and fermion resonances. I will take the Minimal Composite Higgs model as an example, to describe the strategies we use to search for the resonances at the LHC. Both current (Run II) and future (3000/fb) experimental reaches will be shown.

77. Nov 14,  Dr. Kimiko Yamashita (National Tsing Hua University, Taiwan), LHC Searches for Kaluza-Klein Graviton Decaying into SM/DM Particles. file

We study the phenomenology of a massive graviton G with universal and non-universal (top-philic) couplings to the Standard Model (SM) particles. 

Such a particle can arise as a warped Kaluza-Klein graviton from a framework of the Randall-Sundrum extra-dimension model.  We also consider simplified dark matter models where a dark matter candidate couples to the SM particles via a G mediator. We study constraints on the model parameter space from the current LHC data.

Ref: Eur. Phys. J. C 77, no. 5, 326 (2017) (arXiv: 1701.07008), JHEP 1810, 046 (2018) (arXiv1807.09643)

76. Nov 6 (at 4pm, 102-104),  Dr. Jinmian Li (KIAS), Dark Matter Showering in $U_D(1)$ dark gauge group. file

Abstract:

I will first briefly review the recent studies on dark matter showering under unbroken SU(N) gauge group. 

Special attention will be paid to the U(1) dark gauge group case. The model setup, splitting functions as well as the showering algorithm will be introduced. Results and discussion will be made based on three benchmark points of the model.

75. Oct 31,  Dr. Nicolas Bernal (Antonio Narino Univ, Colombia), The Dawn of FIMP Dark Matter file

Abstract:

We present an overview of scenarios where the observed Dark Matter (DM) abundance consists of Feebly Interacting Massive Particles (FIMPs), produced non-thermally by the so-called freeze-in mechanism. In contrast to the usual freeze-out scenario, frozen-in FIMP DM interacts very weakly with the particles in the visible sector and never attained thermal equilibrium with the baryon-photon fluid in the early Universe. Instead of being determined by its annihilation strength, the DM abundance depends on the decay and annihilation strengths of particles in equilibrium with the baryon-photon fluid, as well as couplings in the DM sector. This makes frozen-in DM very difficult but not impossible to test. In this review, we present the freeze-in mechanism and its variations considered in the literature (dark freeze-out and reannihilation), compare them to the standard DM freeze-out scenario, discuss several aspects of model building, and pay particular attention to observational properties and general testability of such feebly interacting DM.

74. Oct 10,  Dr. Chang Sub Shin (IBS-CTPU), Axionic Electroweak Baryogenesis file

Abstract : An axion can make the electroweak phase transition strongly first-order as required for electroweak baryogenesis even if it is weakly coupled to the Higgs sector. This is essentially because the axion periodicity helps to avoid an instability of the potential regardless of the value of the axion decay constant. Furthermore, the axion can serve as a CP phase relevant to electroweak baryogenesis if one introduces an effective axion coupling to the top quark Yukawa operator. Then, for an axion decay constant between about TeV and order 10 TeV, the observed baryon asymmetry can be explained while avoiding current experimental constraints. It will be possible to probe the axion window for baryogenesis in future lepton colliders and beam-dump experiments.

73. Oct 8 (at 4:30pm), Prof. Carsten Rott (Sungkyunkwan University), IceCube - A new Window to the Universe, department colloquium.

Abstract:

The IceCube Neutrino Observatory studies a wide range of phenomena including neutrino astronomy, dark matter searches, neutrino oscillations, and cosmic ray physics using a cubic kilometer of instrumented ice at the South Pole. Recently, we reported evidence for the first identified source of the high energy astrophysical neutrinos (Blazar TXS0506+056). This represents a major milestone towards understanding both the sources of high energy neutrinos and cosmic rays. I will summarize IceCube's recent results and highlight implications of the identification of the high energy neutrino source and how it fits into the broader context of the multi-messenger astroparticle physics field.

Seminars in spring 2018

72. May 31 (at 12pm & 5pm, 102-104), Prof. Koji Ishiwata (Kanazawa University), Effective field theory for direct detection of dark matter. file

Abstract:

I discuss how to construct the effective field theory for the direct detection of dark matter.   Giving some examples, matching procedure is shown in detail.

71. May 23, Dr. Eibun Senaha (IBS-CTPU),  On gauge dependence of first-order phase transitions.  file

Abstract: 

Finite-temperature effective potential is an useful tool for studying thermal phase transitions.

However, a perturbative treatment commonly used in the literature is gauge dependent,

giving rise to irreducible uncertainties in theoretical predictions. 

In this talk, after giving a short review of the gauge dependence of the effective potential, 

I will discuss an impact of the gauge-fixing parameter dependence on a critical temperature

and gravitational wave induced by the first-order phase transition in a massless U(1)_B-L gauge theory. 

Along the same line, I will also talk about the gauge dependence issue in the context of electroweak 

phase transition. After introducing a gauge-invariant calculation scheme proposed by Patel and Ramsey-Musolf, 

I will apply it to a singlet-extended standard model and show our findings.

70. May 21 (at 4:30pm), Prof. Deog-Ki Hong (Pusan National University),  중력이야기 - 추락하는 것은 질량이 있다, department colloquium.

초록 : 자연에 존재하는 기본 힘 가운데 가장 오래된  중력에 대한 우리의 이해가 어떻게 발전해 왔는지를 설명한다.  아인쉬타인의 일반상대론은 중력을 매우 정확하고 아름답게 기술한다. 그러나 다른 기본 힘과는 달리 일반상대론으로 기술되는 중력은 양자역학과 양립되지 세않는다. 이를 해결하는 것은  21세기 물리학의 가장 어려운 문제중의 하나이다. 본 콜로퀴움에서는  최근 끈이론에서 발견된 게이지-중력 이중성으로 부터 어떻게 그 문제 해결의 실마리를 찾을 수 있는지를 살펴본다.

69. May 2, Dr. Ryusuke Jinno (IBS-CTPU), Gravitational waves from first-order phase transitions: an analytic approach to reveal the spectrum structure

Abstract:

Gravitational waves (GWs) from bubble dynamics in cosmological first-order phase transitions, if detected, will give us an important clue to unknown high-energy physics. However, it is not clearly known how such bubble dynamics encodes itself in the resulting GW spectrum. In this presentation I will introduce a recently-developed analytic approach, which make clear the imprint of the bubble-like structure (both from the scalar field configuration and sound waves) in the GW spectrum. This approach will help to extract the information on the underlying particle physics which drives the transition and the bubble dynamics.

References: 

"Gravitational waves from bubble dynamics: Beyond the Envelope", R.Jinno and M.Takimoto, 1707.03111

68. April 11, Prof. Jihn E. Kim (Kyung Hee Univ), Axion rolling through QCD phase transition.

67. April 4, Dr. Kenji Nishiwaki (KIAS),  Vectorlike confinement visits B-meson flavor anomalies and more

Abstract:

Anomalies suggesting lepton flavor violation have been reported as

deviations in the ratios, namely, R_K and R_K(*) and associated variables.

Results of global fits of data tell us that a new Z'-like vector boson

(or vector leptoquark) which couples with corresponding left-handed

components of quarks and leptons is a good candidate for explanation.

On the other hand, consistency in gauge anomaly cancellation puts

a restriction on the choice of quantum number.

In this talk, we focus on the scenario where vector-boson and vector-leptoquark

candidates are naturally realized as `vector-rho mesons' of a hidden

strongly-coupled

vector-like gauge theory, where the theory is manifestly anomaly-free and

the vector particles can contain couplings with the SM fermions in

a gauge-invariant way, in the language of hidden-local symmetry.

We found parameter spaces where the deviation in R_K and R_K(*) is

explained by new physics effects consistently [based on arXiv:1706.01463].

We also introduce the possibility of addressing the deviation of

epsilon'/epsilon in the Kaon system.

Even though the updated ATLAS result on the dimuon resonance puts a severe

bound on our second scenario, we could address both of the deviations

simultaneously

in a limited part of the parameter space [work in progress].

Seminars in fall 2017

66. Nov 27 (at 4:30pm), Prof. Sunghoon Jung (SNU), Looking into the Universe: Higgs Boson and Gravitational Wave, department colloquium.

Abstract:

The Standard Model of particle physics is completed with the discovery of the Higgs boson, but it still has intriguing questions that can only be answered by new physics beyond the Standard Model. With the Large Hadron Collider operating at the highest-ever collision energy and the discovery of the Gravitational Wave, particle physics frontier is making big steps towards answering those questions.

65. Nov 15, Dr. Takashi Toma (Munich Tech Univ), Fermionic Strongly Interacting Massive Particles

Abstract:

Strongly Interacting Massive particles (SIMPs) are alternative dark matter candidates which give a solution for the small-scale structure problems in the universe. Many SIMP models have been proposed so far, and in these models a scalar or vector boson has been identified as a SIMP candidate. In this talk, we consider a fermionic SIMP whose relic abundance is determined by 4-to-2 self-annihilaton processes in dark sector itself through dark thermalization. We show that the 4-to-2 annihilation cross section for spin 1/2 Majorana SIMPs is necessarily suppressed by d-wave at non-relativistic limit due to the Pauli exclusion principle. The interactions between the dark and the visible sectors are feeble, thus the dark sector never reaches thermal equilibrium with the visible sector.

64. Nov 8, Prof. Dumitru Ghilencea (IFIN-HH, Buchrest and CERN), Scalar potential in models with quantum scale invariance

Abstract:  

Spontaneous breaking of quantum scale invariance may provide a solution to the hierarchy and cosmological constant problems.  In a scale-invariant regularization we  compute the one and two-loop corrections  to the scalar potential of the higgs field ($\phi$) in a classically scale invariant model extended by the dilaton ($\sigma$).   The two-loop potential is scale invariant since the loop calculations manifestly preserve this symmetry, with the DR subtraction scale generated dynamically by the dilaton vev.  The potential contains new, non-polynomial effective operators, showing that theories with quantum scale invariance are non-renormalizable. The Callan-Symanzik equation of the potential is verified to two-loop order. The results are compared to the case  of explicit breaking of scale symmetry ($\mu=$constant scale).  We then apply this idea to the scale invariant version of the Standard Model ($m_{higgs}=0$ at tree level) extended by the dilaton and discuss its implications.

63. Nov 1, Prof. Yann Mambrini (Oray LPT), Dark Matter and Early Universe Cosmology. file

62. Sep 20, Dr. Kenji Nishiwaki (KIAS), Vector-like compositeness meets B-physics R_K(*) anomaly. postponed.

Abstract:

Anomalies suggesting lepton flavor violation have been reported as

deviations in the ratios, namely, R_K and R_K*. Results of global fits

of associated data tell us that (a) new Z'-like vector boson which

couples with corresponding left-handed components of quarks and

leptons is a

good candidate for explanation. On the other hand, consistency in

gauge anomaly cancellation puts a restriction on the choice of U(1)'

quantum number. In this talk, we focus on the scenario where

vector-boson candidates are naturally realized as `vector-rho mesons'

of a hidden strongly-coupled vector-like gauge theory, where the

theory is manifestly anomaly-free and the vector particles can contain

couplings with the SM fermions in a gauge-invariant way, in the

language of hidden-local symmetry. We found parameter spaces where the

deviation in R_K and R_K* is explained by new physics effects

consistently. Besides, direct detection of vector rho mesons is

expected at the LHC in the future. We also address situations of

another flavor anomalies of R_D and R_D* in this scenario briefly.

Seminars in summer 2017

61. August 16 (Wednesday at 2:00pm, 102-106), Dr. Ligong Bian (Chung-Ang University), Lecture on Electroweak Baryogenesis and Gravity Waves.

[Abstract]

References:  https://arxiv.org/abs/gr-qc/0107033v1 ; https://arxiv.org/abs/1206.2942

- Schedule -

2:00-3:30pm  Finite temperature field theory and electroweak first order phase transition

4:00pm-5:30pm Gravity wave signals from electroweak phase transition

6:00pm Dinner

Seminars in spring 2017

60. May 29 (Monday at 4:30pm, 102-106), Prof. Hang Bae Kim (Hanyang University), Department Colloquium,  우주론은 어디로 가고 있는가?

[초록]

우주론은 세상이 어떻게 생겼느냐는 궁극적 호기심을 추구합니다.

이 강연에서는 과거에 우주론이 어떻게 발전되어 왔는지와 일반상대성과

입자물리학이 지배하는 시공간과 물질의 동역학인 현대 우주론에 대해 알아보고,

현재의 표준 우주론이 가진 문제점들과 우주론의 미래에 대해서 논의합니다.

59. May 18, Dr. Jaehyeon Park (KIAS),  Vacuum (meta)stability and particle phenomenology,  file

Abstract: Vacuum stability as well as false vacuum decays in quantum field theory are briefly reviewed.  Numerical methods to search for deeper minima and to find the bounce are discussed, which are then followed by a few examples of their applications to and implications for the phenomenology of elementary particles.

58. May 12 (Friday at 3pm, 102-108), Prof. Wan-Il Park (Chonbuk National University), On large lepton number asymmetries of the universe,  file

Abstract: The possibility of a very large lepton number asymmetry in the present universe will be discussed, and a full picture accommodating the large asymmetry will be provided.

57. May 2 (Tuesday at 2pm), Dr. Myeonghun Park (IBS-CTPU),  Understanding dark sector with collider experiments,  file

Abstract: In this talk, I will explain how one can understand the dark sector, including the properties of dark matter with collider, especially the LHC. As examples, I will also cover some non-conventional dark matter scenarios which can have exotic signatures at the LHC.

56. April 27, Dr. Zhaofeng Kang (KIAS),  When dark matter meets neutrino,  file

Abstract:  The existence of dark matter and nonvanishing neutrino masses are two most robust evidences for new physics beyond the particle standard model, respectively. But probably they are connected. In this talk I will demonstrate simple ways to connect them and show interesting things therein.

55. April 17 (Monday at 4pm, 102-805), Prof. Alejandro Ibarra (TUM), "Dark matter decay via the gravity portal" ,  file

Abstract: We consider the Standard Model extended with a dark matter particle in curved spacetime, motivated by the fact that the only current evidence for dark matter is through its gravitational interactions, and we investigate the impact on the dark matter stability of terms in the Lagrangian linear in the dark matter field and proportional to the Ricci scalar. We show that this "gravity portal" induces decay even if the dark matter particle only has gravitational interactions, and that the decay branching ratios into Standard Model particles only depend on one free parameter: the dark matter mass. We study in detail the case of a light singlet scalar and discuss the prospects to observe its gravitationally induced decay.

54. April 14 (Friday), Dr. Seodong Shin (Yonsei), Dark matter “collider” and a new mechanism for cosmic-ray excesses from non-minimal dark sector,  file

Abstract: I will discuss interesting phenomena in direct and indirect detections of a non-minimal dark sector. I will first talk about relativistic collisions of dark matter with targets in current and future neutrino detectors such as Super/Hyper Kamiokande and DUNE, which induces cascade signals in a scenario like inelastic boosted dark matter. Then I will suggest a new mechanism for cosmic-ray excesses: Dark Matter Transporting Mechanism.

53. April 6, Dr. Chang Sub Shin (APCTP), A map of the non-thermal WIMP,  file

Abstract:

In this talk, I will present the effect of the elastic scattering on the non-thermal WIMP, which is produced by direct decay of heavy particles at the end of reheating. The non-thermal WIMP becomes important when the reheating temperature is well below the freeze-out temperature. Usually, two limiting cases have been considered so far. One is that the produced high energetic dark matter particles are quickly thermalized due to the elastic scattering with background radiations. The corresponding relic abundance is determined by the thermally averaged annihilation cross-section at the reheating temperature. The other one is that the initial abundance is too small for the dark matter to annihilate so that the final relic is determined by the initial amount itself. The regions between these two limits are more interesting, and it is showed that the relic density depends not only on the annihilation rate, but also on the elastic scattering rate. Especially, the relic abundance of the p-wave annihilating dark matter crucially relies on the elastic scattering rate because the annihilation cross-section is sensitive to the dark