Dublin Theoretical Physics Colloquia

Colloquium:  12/04/23 - Andrea Shindler (Michigan State U.)

Title: Unravelling matter-antimatter asymmetry in the universe

Abstract: The observed baryon asymmetry in the universe cannot be reconciled with the current form of the Standard Model (SM) of particle physics. The amount of CP-violation stemming from the Cabibbo-Kobayashi-Maskawa matrix is not sufficient to explain the observed matter-antimatter asymmetry. Historically, one of the first systems to be studied in the search for CP-violation is the electric dipole moment (EDM) of the neutron. The contribution to the neutron EDM coming from the SM is several order of magnitudes smaller than the current experimental bound, thus providing a unique background-free window for potential discovery of physics Beyond the Standard Model (BSM). After a brief summary of the current status for experimental searches of a neutron EDM, I describe the different CP-violating sources and the challenges that present a calculation of the corresponding hadronic matrix elements. I then proceed detailing recent results obtained, with my collaborators, on the neutron EDM with a specific focus on the the main theoretical and numerical tool used: the gradient flow. I conclude with near-term goals, challenges and an optimistic view into the future.

If not stated otherwise, colloquia are in SALMON Lecture Theatre (Hamilton building, groud floor) at 4pm.

The webpage of the season 2021-22 can still be reached here: 

https://sites.google.com/view/tcd-colloquiums-and-seminars/home

Organizers:  Patrick Fritzsch & Fabrizio Nieri

PAST EVENTS:

Colloquium:  05/04/23 - Alba Grassi (Geneve U.)

Title: Seiberg-Witten theory and black holes

Abstract: In recent decades, the field of physical mathematics has undergone remarkable developments, yielding to numerous powerful results. Among them is the discovery of connections between quantum spectral problems on the one hand, and supersymmetric gauge theory or topological string theory on the other. In this talk I will review some aspects of this correspondence and present an intriguing new connection between such framework and black holes.

Colloquium:  29/03/23 (ZOOM) - Antonio Rago (CERN/Plymouth U.)

Title: Multi-particle observables from pure Yang-Mills

Abstract: The building blocks of QCD, quarks and gluons, and their interactions lead to a rich variety of observed phenomena. A particularly intriguing aspect of QCD physics is the nature and behaviour of resonances: short-lived states that decay via the strong force. In this talk, I will discuss progress in studying these states, by calculating multi-particle observables in the simplified framework of pure Yang-Mills. In particular, I will focus on the idea of using finite volume as a tool to extract dynamical observables such as the couplings of the states.

Colloquium:  22/03/23 - Julian Sonner (Geneva U.)

Title: What is a chaotic CFT?

Abstract: In this talk I will define a notion of approximate CFT and explain how to construct suitable ensembles of CFT data that allow us to construct averaged CFTs. Such theories are natural generalisations of ensembles of random matrices describing the ergodic phases of quantum chaotic many-body systems. I will then specialise to the case of two dimensions and demonstrate that the ensemble of CFT data takes the form of a random tensor model of the Virasoro 6j symbol. Models of this type have been considered previously as discrete lattice actions of 3D gravity.

Colloquium:  22/02/23 - Victoria Martin (Edinburgh U.)

Title: The Higgs Era - 10 years of Higgs boson physics

Abstract: Last year, 2022, marked 10 years since the announcement of the discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider at CERN, and the start of the Run 3 of the LHC. In this colloquium, I will review what ATLAS measurements of the Higgs boson with LHC Runs 1 & 2, and the prospects for Higgs boson physics with Run 3 and beyond.

Colloquium:  15/02/23 - Yolanda Lozano (Oviedo U.)

Title: Prospects of AdS/CFT in low dimensions 

Abstract: We will review recent developments in the study of the AdS/CFT correspondence for low dimensional conformal field theories, and its applications to the description of defects and black holes.

Colloquium:  08/02/23 (ZOOM) - Pilar Hernández (Valencia U.)

Title: The imprint of the baryon asymmetry in neutrino physic

Abstract: The origin of neutrino masses remains a mystery but most extensions of the Standard Model that can explain neutrino masses also provide a new mechanism to explain the asymmetry between matter and antimatter that we observe in the Universe today. In this talk I will give an overview of the recent progress in neutrino physics and its connections to baryogenesis.

Colloquium:  01/02/23 - Henrik Johansson (Uppsal U.)

Title: Scattering amplitudes for Kerr black holes and higher-spin gauge symmetry

Abstract: In a series of recent works it has become clear that quantum scattering amplitudes can be used to gain surprisingly useful insights to the dynamics of Kerr black holes. A simple infinite family of three-point amplitudes have been found, which describes the primary gravitational interaction of a black hole with quantum spin s. However, the corresponding Compton four-point amplitudes are not known except for a few low-spin examples. These amplitudes are needed for post-Newtonian and post-Minkowskian calculations of inspiraling binary black-hole systems. In this talk, I will show that all known Kerr amplitudes can be uniquely predicted from the principle of gauge symmetry. In particular, I will discuss the construction of a family of EFTs with Stuckelberg higher-spin fields that describe the expected dynamics of Kerr black holes. The EFTs enjoys massive higher-spin gauge symmetry, which is used as a selection principle for the non-minimal interactions. I will briefly discuss a possible interpretation of this symmetry, and give an outlook towards future work.  

Colloquium:  25/01/23 - Hartmut Wittig (Mainz U.)

Title: Precision Tests of the Standard Model and the Role of Lattice QCD

Abstract: While the Standard Model of particle physics provides a quantitative description of the properties of the known constituents of visible matter, it fails to explain the existence of dark matter or the baryon asymmetry in the uninverse. An increasingly important strategy to search for "new physics" is based on confronting highly precise experimental data with theoretical predictions. The sensitivity of such precision tests of the Standard Model is often limited by the effects of the strong interaction. In this talk I will discuss recent calculations of hadronic contributions to precision observables in lattice QCD. Quantities include the anomalous magnetic moment, as well as the electromagnetic and electroweak couplings. Particular attention will be given to comparisons with traditional "data-driven" evaluations of these quantities and the consistency with constraints from global electroweak fits.

Colloquium:  30/11/22 - Massimo Taronna (Naples U.)

Title: Inflation as a hologram

Abstract: Looking for a consistent description of quantum mechanical and gravitational phenomena, we are inevitably led to define observables living at infinity. This is the common mantra that there are no local observables in quantum gravity and provides a tantalising motivation for a purely boundary--or holographic--description of physics in the interior.  The AdS/CFT correspondence provides an important working example of these ideas, where the boundary description of quantum gravity in anti-de Sitter (AdS) space is an ordinary quantum mechanical system — a Lorentzian Conformal Field Theory (CFT). It would be desirable to have a similar level of understanding for the universe we actually live in. In this talk I will explain some recent efforts that aim to understand the rules of the game for observables on the future boundary of de Sitter (dS) space. Unlike in AdS, the boundaries of dS space are purely spatial with no standard notion of locality and time. This obscures how the boundary observables capture a consistent picture of unitary time evolution in the interior of dS space. I will explain how, despite this difference, the structural similarities between dS and AdS spaces allow to forge relations between boundary correlators in these two space-times. These can be used to import techniques, results and understanding from AdS to dS at any order in perturbation theory and beyond.

Colloquium:  23/11/22 - Martin Lüscher (CERN/Bern U.)

Title: Chiral symmetry, the topological charge and the Yang-Mills gradient flow

Abstract: This talk is about an old issue that arose after the instantons were discovered and numerical lattice gauge theory became a popular subject. The question is whether the division of the field space in topological sectors is a property of QCD at the fully non-perturbative level or merely an emergent asymptotic feature of the theory in the semi-classical limit. Exactly how the topological susceptibility and the higher moments of the topological charge distribution are defined beyond the semi-classical level is in fact not obvious, since the formal expressions for the moments are manifestly ultraviolet-divergent. Important conceptual developments in lattice QCD (formulations preserving chiral symmetry and the proof of the finiteness of the Yang-Mills gradient flow) eventually permitted the question to be answered and moreover led to expressions for the moments, which are finite, regularization-independent and consistent with the chiral Ward identities.

Colloquium:  16/11/22 - Joseph Minahan (Uppsala U.)

Title: Supersymmetric Yang-Mills in 7 dimensions and supergravity

Abstract: In this talk I will describe how to use localization and holography to explore different regions of maximally supersymmetric Yang-Mills on the seven-dimensional sphere.  In analogy to half-maximal super Yang-Mills in five dimensions, we argue that in seven dimensions there is a regime where the renormalized coupling squared is negative but the theory is still sensible.  In this regime there can be membranes with arbitrarily small tensions.

Colloquium:  09/11/22 - Alexander Rothkopf (Stavanger U.) 

Title & Slides: Open Quantum Systems: Thermometry at the Extremes

Abstract: The study of quantum systems coupled to an environment plays a vital role in how we measure temperatures of the coldest and hottest matter in the universe. The strategy relies on introducing impurities into the system of interest and on observing how these probe particles evolve towards or in equilibrium with their surroundings. From these observations we may in turn deduce the thermal properties of the environment. Originally studied in the context of condensed matter physics, open quantum systems nowadays provide a common language to research spanning multiple orders of magnitude in temperature, ranging from Bose Einstein condensates made of ultracold atoms to the Quark-Gluon plasma created in ultra-relativistic collisions of heavy ions. This talk builds a bridge between polaron impurities in the former to quarkonium particles in the latter as two manifestations of quantum Brownian motion, a phenomenon ideally described by open quantum systems.

Colloquium:  02/11/22 - Mari Carmen Bañuls (Munich U.)

Title & Slides: Tensor Networks: entanglement and the simulation of quantum many-body problems

Abstract: The term Tensor Network States (TNS) designates a number of ansatzes that can efficiently represent certain states of quantum many-body systems. In particular, ground states and thermal equilibrium of local Hamiltonians, and, to some extent, real time evolution can be numerically studied with TNS methods. Quantum information theory provides tools to understand why they are good ansatzes for physically relevant states, and some of the limitations connected to the simulation algorithms. These methods were originally introduced in the context of condensed matter, but they are applicable to a large variety of problems.  As an example, in the last few years it has been shown that TNS are also suitable to study lattice gauge theories and other quantum field problems. This talk will present the main ideas, as well as the possibilities and limitations of tensor network techniques, and some of their recent applications.

Colloquium:  12/10/22 - Andrea Puhm (Ecole P.)

Title: Holography and the Celestial Sphere

Abstract: I will review recent advances in Celestial Holography - the conjecture that quantum gravity in asymptotically flat spacetimes is dual to a co-dimension two conformal field theory (CFT) on the celestial sphere at null infinity. The basic observable in quantum gravity is the S-matrix which, when recast in a basis of boost eigenstates, shares properties with CFT correlation functions. Many of its universal aspects such as soft and collinear limits take a natural form in CFT language. Furthermore, harnessing the power of conformal representation theory allows us to determine the operators associated to the symmetries of celestial CFTs and understand how they encode the spacetime asymptotic symmetries. I will discuss these and more recent developments on extending celestial holography to non-trivial asymptotically flat backgrounds and to any number of dimensions.

Colloquium:  05/10/22 - Sergei Gukov (DIAS)

Title: Machine Learning in Theoretical and Mathematical Sciences

Abstract: TBA

Colloquium: 28/09/22 - Gregory Korchemsky (IPhT) - CANCELED !!!

Title: Solving AdS/CFT with the strong Szego limit theorem

Abstract: The strong Szegö limit theorem describes asymptotic behavior of determinants of large Toeplitz matrices. It has important applications in theoretical physics, ranging from two-dimensional Ising model to the theory of random matrices. In this talk, I will show how this theorem can be effectively applied to computing four-point correlation functions of infinitely heavy half-BPS operators in planar N = 4 SYM for arbitrary coupling constant.