### Talks

General information:

1. RIKEN Lunch Seminar starts at 12:30 PM on Thursday, Room 2-160 or 2-95.

2. To order Japanese lunch box, send a message to the organizer or stop by his office.
For lunch menu, going to the left sidebar Lunch.
Note: you need to place the order by 6:00 PM on Wednesday.

3. Click the title of the talk, you could download the slides of the talk.
For a full list of all future talks, going to the left sidebar List.

Organizers: Daniel Pitonyak (Room 2-52), Hiroshi Oki (Room 2-44), Chris Kelly (Room 2-44)

8/4/2016

Photon-jet Ridge at RHIC and the LHC

Amir Rezaeian (Federico Santa Maria Technical University)

I will talk about inclusive prompt photon and photon-jet production in p+A collisions at RHIC and the LHC. In particular, I show that photon-jet correlations in the Color Glass Condensate (CGC) picture exhibit long-range azimuthal collimation at near-side for low transverse momenta of the produced photon and jet in high-multiplicity events. These ridge-like features are strikingly similar to the observed ridge effect for di-hadron correlations at RHIC and the LHC.  I show that correlations in the relative rapidity and the relative azimuthal angle between pairs of prompt photon and jet strongly depend on the gluon saturation dynamics at small-x kinematics and such measurements can help to understand the true origin of the observed di-hadron ridge in p+A collisions, and address whether the ridge is a universal phenomenon for all two particle correlations at high energy and high multiplicity events.

6/16/2016

Static and dynamic screening effect on the resonant $\alpha-\alpha$ scattering in a QED plasma

Xiaojun Yao (Duke University)

The plasma screening effect on the low-energy $\alpha-\alpha$ ($^4$He-$^4$He) scattering is studied by using the pionless effective field theory and thermal field theory. It is known that in vacuum a resonance lies at the center-of-mass energy 91.84 keV with a width 5.57 eV, identified as $^8$Be. It is found that the static (Debye) screening decreases the resonance energy and width. A bound state starts to form when $m_D>0.3$ MeV. However, when the dynamic screening effect is included, which results in an imaginary potential (damping rate), both the resonance energy and width increase with the plasma temperature. Then the screening effect on the thermal nuclear reaction rate is studied and found to suppress the rate by more than 100 times when the temperature is 10 keV around. It is speculated that these may have implications on other nuclear reaction rates that are of great interest in cosmology and astrophysics.

5/26/2016

Lefschetz-thimble path integral for studying the sign problem and Silver Blaze phenomenon

Yuya Tanizaki (RBRC)

Recently, Picard-Lefschetz theory gets much attention in the context of the sign problem, because it enables us to study the system with the complex classical action nonperturbatively by employing the semiclassical analysis. In this seminar, after its brief introduction, I will apply it to the one-site Hubbard model. This model has a severe sign problem, which looks quite similar to that of the finite-density QCD at low temperatures. By solving this model using the Lefschetz-thimble path integral, we are trying to understand the structure of the sign problem of finite-density QCD. Especially, I give a qualitative picture (or speculation) about the early-onset problem of the baryon number density, called the baryon Silver Blaze problem. The complex Langevin method will also be discussed if time allows.

5/19/2016

Kosterlitz-Thouless transition and chiral rotation in external electromagnetic field

Gaoqing Cao (Fudan University)

In 2+1 dimensional system, the most important phase transition should be of the Kosterlitz-Thouless (KT) type. We determined the KT transition temperature T_KT as well as the mass melting temperature T^* as a function of the magnetic field. It is found that the pseudogap domain T_KT < T < T^* is enlarged with increasing strength of the magnetic field. The influence of a chiral imbalanceμ_5 was also studied. We found that even a constant axial chemical potential μ_5 can lead to inverse magnetic catalysis of the KT transition temperature in 2+1 dimensions. This is actually the de Haas-van Alphen oscillation. Furthermore, we studied the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant I_2=E·B. We showed that the presence of I_2 can induce neutral pion (π_0) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu-Jona-Lasinio model at leading 1/Nc expansion, a universal dependence of the π_0 condensate on I_2 was found. The stability of the π_0-condensed vacuum is also discussed.

5/12/2016

The Functional Renormalization Group Method and Delayed Magnetic Catalysis

Stefan Rechenberger (University of Darmstadt)

This talk will start with a very general introduction to the Functional Renormalization Group method, a powerful non-perturbative tool which can be applied to various problems. The second part of the talk will demonstrate this by discussing the influence of an external magnetic field on the chiral phase transition in the theory of strong interaction. The Functional Renormalization Group analysis shows that, driven by gluon dynamics, the chiral critical temperature decreases for small values of the magnetic field. For large values of the external field, however, the phase transition temperature increases.

5/5/2016

Vorticity in heavy-ion collisions and cold atoms

Xu-Guang Huang (Fudan University)

Vorticity describes the local rotation of the fluid. I will talk about our recent study of the event-by-event generation of flow vorticity in heavy-ion collisions. Several special properties of the vorticity in heavy-ion collisions will be discussed, e.g., the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction. Vorticity can drive vector and axial current in chiral quark-gluon plasma via the chiral vortical effect. I will discuss the collective gapless mode, the chiral vortical wave, emerging from CVE and its experimental implications in heavy-ion collisions. Finally, I will consider the rotating trapped cold atomic gases and show that when there is a Weyl spin-orbit coupling such cold atomic gases provide a desktop simulator of the chiral magnetic effect and chiral separation effect.

4/28/2016

Solving QCD2

Alexei Tsvelik (BNL)

We study a (1+1)-dimensional version of the famous Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and finite chemical potential. We use non- perturbative techniques (non-Abelian bosonization and Truncated Conformal Space Approach). At zero chemical potential we describe a formation of fermion three-quark (nucleons and ∆-baryons) and boson (two-quark mesons, six-quark deuterons) bound states and also a formation of a topo- logically nontrivial phase. When the chemical potential exceeds the critical value, the model has a rich phase diagram which includes phases with density wave and superfluid quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results as a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).

4/21/2016

Color fluctuation phenomena in high energy hadron & photon-A collisions

Mark Strikman (Penn State University)

Compositeness of the bound states and the Lorentz slowing down of high energy interactions in QED and QCD lead to emergence of new coherent phenomena. We focus on the phenomena related to the fluctuations of the strength of interaction  (color fluctuations  phenomena). First we consider gross violations of the Glauber model for centrality dependence of production of the leading jets in pA scattering  predicted earlier within QCD and recent evidence for this phenomenon  from the studies of hard pA collisions at the LHC  and dAu collisions at RHIC.  Color fluctuations also explain a large suppression of the  cross section of coherent vector meson  photoproduction as compared to the Glauber model  observed recently in the ultraperipheral collisions at LHC.  We outline perspectives of future studies of the color fluctuation phenomenon in ultraperipheral heavy ion collisions at the LHC and electron - nucleus colliders.

3/31/2016

Sphalerons Far From Equilibrium and Associated Phenomena

Mark Mace (Stony Brook University)

In this talk, I will present a first computation of sphalerons in the glasma; the highly occupied, weakly coupled gluon dominated pre-equilibrium matter created at early times after an ultra-relativistic heavy ion collisions. The sphaleron transition is a well known ingredient in the generation of anomalous vector current from a strong external magnetic field, the so-called Chiral Magnetic Effect. We perform classical-statistical real-time lattice simulations to study the dynamics of these topological transitions; simplifying our description by employing SU(2) gauge fields and neglecting the longitudinal expansion for this first study. I will show that the non-equilibrium sphaleron transition rate is time dependent and non-Markovian, in addition to being dominant in comparison to the thermal equilibrium sphaleron transition rate. In addition, we can measure the scaling and separation of physical scales in analogy to those from thermal equilibrium, in order to parameterize this rate and understand the approach to equilibrium. I will then demonstrate that it is the magnetic screening length, which we extract non-perturbatively, that controls this rate. Additionally, I will briefly mention studies of related anomalous transport effects that we plan on studying using this first principles classical-statistical real-time lattice technology.

3/3/2016

Investigation of anomalous dynamics and the Chiral Magnetic Effect far from equilibrium

Niklas Mueller (University of Heidelberg)

We investigate the impact of the Adler-Bell-Jackiw axial anomaly on the real-time dynamics of gauge theories in the strong field regime. By studying and comparing Abelian gauge theories, such as QED, with non-Abelian systems, we
try to clarify the role of topological properties and initial conditions relevant far from equilibrium. We show that the Abelian version of the Chiral Magnetic Effect, which has been predicted in the context of ultra-relativistic heavy ion collisions, can result in non-trivial experimental signatures,  which could possibly be observed in future high-intensity laser experiments. Further I will report on recent investigations of chiral production mechanisms in strong non-Abelian gauge fields and I will discuss the influence of topological objects such as sphalerons, far from equilibrium. Moreover I will show first results of the studies we have undertaken since my arrival here at BNL and discuss how the combination of these studies might be used to shed more light on the role played by anomalies in the early stages of a heavy ion collision.

1/14/2016

Confinement and Chiral symmetry breaking from an Interacting Instanton-dyon ensemble for 2 colors and Nf flavors

Rasmus Larsen (Stony Brook University)

I will present numerical results based on an interacting ensemble of instanton-dyons, that explains the connection between chiral symmetry breaking and confinement. The instanton-dyons have the nice properties to behave as monopoles at low temperatures, and as instantons at high temperatures. We will see how the scaling behavior of the instanton-dyons creates a Polyakov loop dependent potential, which forces the Polyakov loop to the confining value as the density of dyons increases at lower temperatures. For 2 flavors we find that the dominating configuration in the ensemble exhibit a chiral symmetry transition at the same temperature as the confinement transition, within accuracy.  The important factor in explaining confinement and chiral symmetry breaking is the density of the Instanton-dyons.

12/17/2015

Baryon interactions from Lattice QCD by Luscher's finite volume method and HAL QCD method

Takumi Iritani (Stony Brook University)

Both Luscher's finite volume method and HAL QCD method are used
to analyze the hadron-hadron interaction in lattice QCD.

However, some systematic discrepancies are reported between them.
For example, Luscher's method shows the bound states of
both deuteron and di-neutron at the heavy pion mass,
while these channels are scattering states from HAL QCD method.

In this talk, to understand the deviations between them,
we investigate the baryon interaction from both methods with the same lattice setups.
From a systematic comparison of two methods, we clarify the problems in the previous studies.
We also discuss the improvement of the analyses.

12/10/2015

Phase structure of lattice QCD with Wilson and twisted-mass fermions including isospin breaking

Derek Horkel (University of Washington)

As the precision frontier of particle physics continues to
develop, the field of lattice QCD has risen to the challenge. Modern
lattice simulations, have increasingly included light non-degenerate up and
down quark masses and electromagnetism. Previously answered questions about
the vacuum structure of QCD on the lattice must be reexamined when these
isospin breaking effects are included. If not careful, lattice
practitioners may simulate in non-physical phases which cannot be
extrapolated to the continuum limit. Using chiral perturbation theory, I
will discuss where these non-physical phases can arise for Wilson and
twisted mass fermions. I will also explain some of the complications which
arise when tuning the up and down twisted quark masses to their critical
values in the presence of electromagnetism.

12/03/2015

Sterile neutrino dark matter produced after the QCD phase transition

Louis Lello (University of Pittsburgh)

Sterile neutrinos are SU(2) singlets that mix with active neutrinos via a mass matrix, its diagonalization leads to mass eigenstates that couple via standard model vertices. We study the production of sterile neutrinos in the early universe from pion decays shortly after the QCD phase transition in the absence of a lepton asymmetry. We introduce the quantum kinetic equations that describe their production, freeze out and decay and discuss the various processes that lead to their production in a wide range of temperatures assessing their feasibility as dark matter candidates. We consider the production of heavy neutrinos in the mass range < 140MeV from pion decay shortly after the QCD crossover including finite temperature corrections to the pion form factors and mass. We consider the different decay channels that allow for the production of heavy neutrinos showing that their frozen distribution functions exhibit effects from "kinematic entanglement" and argue for their viability as mixed dark matter candidates. We discuss abundance, phase space density and stability constraints and argue that heavy neutrinos with lifetime >1/H0 freeze out of local thermal equilibrium.

11/19/2015

Viscous Velocity Gradient Correction to Thermal Photon Emission Rate at Strong Coupling

Kiminad Mamo (University of Illinois at Chicago)

We compute the correction to the thermal photon emission rate in first order of shear components of fluid velocity gradients in near-equilibrium hydrodynamic plasma at strong coupling regime using the real-time Schwinger-Keldysh formalism in AdS/CFT correspondence. We find that the gradient correction to the thermal photon emission rate at strong coupling is about 0.3 - 0.4 times of the equilibrium rate.

11/12/2015

Gluon-fusion Higgs production: the final frontier

Elisabetta Furlan (ETH, Zurich)

The gluon-fusion Higgs production cross section has been recently computed through the next-to-next-to-next to leading order (N^3LO) in QCD. This unprecedented level of accuracy is crucial to exploit fully the LHC data in the validation of the Standard Model and in the search for potential (small) deviations due to new physics. I will give an overview of the tools that we employed to achieve this result, from the framework of heavy-quark effective theories to the analytical and mathematical machinery that we developed. I will conclude with some results and future prospects.

11/05/2015

Neural Engineering, Healing the Brain Through Electromagnetic Stimulation

Video from slides

Adam Lichtl (Delta Brain, Inc.)

Two very interesting trends have started to develop in the medical research community. First, in addition to longevity of life through cardiac health, scientists are making increasingly larger strides towards quality of life through neurological health. Second, medical devices are proving their value as complements, and sometimes alternatives, to pharmaceutical interventions. Neural engineers view the brain as an integrated system, and seek to apply engineering principles to achieve healthy brain function. This talk will discuss the history and recent advances in the area of neurostimulation (the use of electromagnetic energy deposited directly into brain tissue), where this field is going, and some of the challenges and opportunities researchers face on the road to commercializing their breakthroughs.

10/22/2015

Walking and conformal dynamics in many-flavor QCD

Hiroshi Ohki (RBRC)

We present our lattice results of SU(3) gauge theory with many flavors, in particular with Nf=8, as a model of a walking or conformal gauge theory. We study the scaling properties of various hadron spectra including the (pseudo)scalar, vector, and baryon channels. From the Nf dependence of the theory, possible signals of walking or conformal dynamics will be discussed.

10/15/2015

pQCD thermodynamics with massive quarks

Thorben Graf (Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität)

Results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential in perturbative QCD at finite temperature and chemical potential including non-vanishing quark masses are presented. These results are compared to lattice data and to higher-order optimized perturbative calculations to investigate the trend brought about by mass corrections. Furthermore, the equation of state for nonvanishing isospin density was investigated within the introduced framework and the findings are also presented.

09/03/2015

Analytic solution of the Boltzmann equation in the early universe

Jorge Noronha (University of Sao Paulo)

A general method for exactly computing the nonlinear collision term of the Boltzmann equation for a massless relativistic gas in a homogeneous and isotropic spacetime is presented. This approach is used to find an exact analytical solution of the nonlinear relativistic Boltzmann equation in a Friedmann-Robertson-Walker spacetime. This solution can be used to investigate analytically the interplay between global expansion and local thermalization in rapidly evolving systems.

08/13/2015

Discrimination of large quantum ensembles

Emilio Bagan (GIQ, Physics Dept., UAB, Spain and Hunter College of the CUNY)

Hypothesis testing is arguably the most common and elementary task in information processing (e.g., we constantly make decisions based on incomplete information).  Its quantum version, quantum state discrimination, is likewise central in quantum information processing. The talk gives an introduction to the topic, focussing on discrimination of a large amount of identically prepared systems. In this limit, a powerful bound on the error rate can be derived. In classical statistics this is know as Chernoff bound. The quantum version of the Chernoff bound will be presented and discussed.

07/30/2015

Ho-Ung Yee (University of Illinois at Chicago)

The P-odd spectral density of current correlation functions appears in several physical observables which are related to chiral anomaly, and is a sensitive probe of microscopic dynamics which is less protected by symmetry alone. We discuss two examples of their appearance: photon emission and the second order transport coefficient from chiral anomaly. We describe leading order weak coupling computations for these examples.

07/02/2015

Chia Cheng Chang (University of Illinois at Urbana-Champaign)

06/25/2015

Jacobus Verbaarschot (Stony Brook University)

The chiral condensate of one-flavor QCD is continuous when the quark mass crosses zero. In the sector of fixed topological charge though, the chiral condensate becomes discontinuous at zero mass in the the thermodynamical limit. To reconcile these contradictory observations, we have evaluated the spectral density of the Dirac operator in the epsilon domain of  one-flavor QCD. In this domain,  we have obtained exact analytical expressions which show that the spectral density at $\theta = 0$  becomes a strongly oscillating  function for negative quark mass with an amplitude that increases exponentially with the volume. As is the case for QCD at nonzero chemical potential, these strong oscillations invalidate the Banks-Casher formula and result in a chiral condensate that is continuous as a function of the quark mass. An additional subtlety is the effect of the topological zero modes which will be discussed as well

We show by solving Maxwell's equations in the presence of chiral magnetic current that the chiral anomaly would induce the inverse cascade of magnetic helicity. We found at late time, the evolution of magnetic helicity spectrum is self-similar and axial charge decays as a power law in time. We visualize how a linked magnetic configuration would evolve into a knotted configuration in real space during such evolution.

06/04/2015

Antonio Vairo (Munich Technical University)

05/21/2015

Piotr Warchol (Jagiellonian University)

I will present a study of the time evolution of Ginibre matrices whose elements undergo Brownian motion. The non-Hermitian character of the Ginibre ensemble binds the dynamics of eigenvalues to the evolution of eigenvectors in a non-trivial way, leading to a system of coupled nonlinear equations resembling those for turbulent systems. We will formulate a mathematical framework allowing simultaneous description of the flow of eigenvalues and eigenvectors, and  unravel a hidden dynamics as a function of new complex variable, which in the standard description is treated as a regulator only. We shall solve the evolution equations for large matrices and demonstrate that the non-analytic behavior of the Green’s functions is associated with a shock wave stemming from a Burgers-like equation describing correlations of eigenvectors.
I will start by reviewing similar notions in a simpler, Hermitian setting.
Joint work with Zdzislaw Burda, Jacek Grela, Maciej A. Nowak and Wojtek Tarnowski (Phys.Rev.Lett. 113 (2014) 104102).

05/14/2015

Michal Praszalowicz (Jagiellonian University)

Geometrical is a consequence of a traveling wave solution of the non-linear QCD evolution equation, so called Balitski-Kovchegov equation. We shall demonstrate the existence of GS in various high energy reactions. Among different consequences of GS there is a linear rise of charged particle multiplicity (Nch) and mean transverse momentum (pT) with scattering energy. Furthermore, a correlation of meant pT and Nch is predicted to scale in a way that depends on the the way particles are produced from the volume excited in a hadron-hadron scattering. This is mostly visible in heavy ion collisions at different centralities.

05/07/2015

NLO transverse momentum broadening and QCD evolution of qhat

Hongxi Xing (LANL)

QCD factorization theorems are essential tools to probe the internal structure of nucleons and nuclei from high-energy scattering experiments. These theorems have been well established for single patron scattering framework. Formal arguments of factorization have also been given by Qiu and Sterman in the 1990s for physical processes where multiple scatterings are important. In this talk, we show you the first complete next-to-leading order (NLO) calculation of transverse momentum broadening in SIDIS e+A and DY p+A collisions. We demonstrate how QCD factorization holds for multiple parton scattering, as well as the universality of the associated quark-gluon correlation function. This further implies that properties of nuclear matter contained therein as probed by a propagating parton are independent of the hard processes that create the fast partons. Our calculation also identifies the QCD evolution equation for this quark-gluon correlation function, which determines the QCD scale and jet energy dependence of the jet transport parameter (qhat).

04/02/2015

### Spin-Orbit Coupling in an Unpolarized Heavy Nucleus

Matt Sievert (BNL)

The next-generation Electron-Ion Collider (EIC) will make high precision measurements of spin-dependent observables at high energies on nuclear targets. This unique nuclear physics laboratory will bring together access to the multitude of spin-spin and spin-orbit structures which can exist in hadronic targets, and the high color-charge densities which generate the most intense gluon fields permitted by quantum mechanics. The interplay between those two features gives rise to new physical mechanisms which translate these spin-orbit structures into the observed cross-sections, and it makes these mechanisms amenable to first-principles calculation. In this talk, I will discuss the spin-orbit structure of quarks within an unpolarized heavy nucleus in the quasi-classical approximation. The possibility of polarized nucleons with orbital motion inside the unpolarized nucleus generates nontrivial mixing between the spin-orbit structures of the nucleons, and the corresponding structures in the nucleus. This generic feature of a dense quasi-classical system leads to direct predictions testable at an EIC, and in principle allows direct access to the orbital angular momentum in the nucleus.

We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization.

01/15/2015

The axial U(1) symmetry though an anomalous symmetry is believed to affect the order of the chiral phase transition in QCD with two light quark flavours. In this talk I discuss about our study of the axial anomaly in finite temperature QCD using first principles lattice gauge theory technique. We use chiral overlap fermions to probe the underlying topology of dynamical QCD configurations with two light quark flavors generated with Highly improved staggered quarks. From the eigenvalue spectrum of the overlap operator we find no evidence of effective restoration of axial symmetry near the chiral transition temperature $T_c$. A pile up of the near--zero eigenmodes is observed to persist even at $1.5 T_c$ which is primarily responsible for its breaking. These eigenmodes are localized unlike those in the bulk, with a mobility edge similar to a Mott--Anderson like system. We find evidence of a dilute gas of instantons at the highest temperature studied, as the microscopic origin of the breaking of U(1).

12/18/2014

Hans-Peter Schadler (University of Graz)

In this talk we will explore the expansion in the fugacity parameter exp(mu beta) as a possible method for lattice QCD to extract generalized quark number susceptibilities at finite baryon chemical potential. These quantities are expected to be good probes for the phase transition in QCD and for the search of a possible critical point. In the fugacity expansion these observables take a simple form and we calculate them up to the 4th order. Furthermore, we determine their ratios and compare them to model calculations.

One of the most important issues in cosmology is about making clear about dark energy. The dark energy accelerates expansion of the universe, but it is known only about the energy has negative pressure. For this study, wide survey with Large Synoptic Survey Telescope(LSST) is being planed. The purpose of the survey is constraining the cosmological parameters including equation of state of dark energy strongly, and so it requires us to analyse with high precision. Tree ring effect is one of the many effects we need to consider for the precise analysis. This effect comes from impurity   in silicon crystal layer in CCD sensor, and changes shape of observed object images. We studied how this affects in constraining the cosmological parameters.

12/04/2014

Nils Strodthoff (Heidelberg University)

In the first part of my talk I will report on progress towards a quantitative first-principle continuum approach to QCD, focusing on recent results for quenched QCD obtained in the framework of the Functional Renormalization group. In the second part I will address more dynamical questions related to the calculation of spectral functions in this framework and discuss, as an application, the calculation of the shear viscosity in Yang-Mills theory over a large temperature range using gluonic spectral functions as only input.

11/20/2014

Jacquelyn Noronha-Hostler (Columbia University)

The interplay between shear and bulk viscosities on the flow harmonics, $v_n$'s, at RHIC is investigated using the newly developed relativistic 2+1 hydrodynamical code v-USPhydro that includes bulk and shear viscosity effects both in the hydrodynamic evolution and also at freeze-out.  While shear viscosity is known to attenuate the flow harmonics, we find that the inclusion of bulk viscosity decreases the shear viscosity-induced suppression of the flow harmonics bringing them closer to their values in ideal hydrodynamical calculations. Depending on the value of the bulk viscosity to entropy density ratio, $\zeta/s$, in the quark-gluon plasma, the bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics may require a re-evaluation of the previous estimates of the shear viscosity to entropy density ratio, $\eta/s$, of the quark-gluon plasma previously extracted by comparing hydrodynamic calculations to heavy ion data.

11/13/2014 (2-95)

Kirill Boguslavski (University of Heidelberg)

Strongly correlated quantum systems have been observed to approach non-thermal fixed-points of their real-time evolution during the thermalization process. Such fixed-points form universality classes far from equilibrium, which are insensitive to a wide range of initial conditions and may be shared by different many-body systems. In this talk, I will present theoretical evidence using classical-statistical simulations that important aspects of longitudinally expanding non-Abelian plasmas in the ultra-relativistic limit admit a dual description in terms of a Bose condensed scalar field theory. Exploring the entire momentum range of the scalar attractor, a low momentum fixed-point is identified that shares universal properties with superfluid Bose gases.

11/07/2014 (NT Seminar, Small Seminar Room)

Derivation of the Hydrodynamic Equation from the Quantum Transport Equation

Yuta Kikuchi (Kyoto University)

We have derived the causal hydrodynamic equation from the Boltzmann equation including quantum statistical effect with the renormalization group method. In this talk, I briefly explain the procedure to obtain the causal hydrodynamics with the renormalization group method and show the obtained equations. Our microscopic expressions for transport coefficients are different from ones derived with any other formalisms and take plausible forms. Furthermore, I also show the causal hydrodynamic equation in the reactive multi-component system which we recently derived.

11/06/2014 (Joint RIKEN Lunch / NT Seminar, 2-160)

Some results on Lattice QCD at the physical point: SU(2) chiral perturbation theory and some words about hadron vacuum polarization

Alfonso Sastre (Bergische Universitaet Wuppertal)

I will present results of a study of the chiral behavior of the pion mass and decay constant, based on 2+1 flavor lattice QCD simulations. Performed at four values of the lattice spacing and all the way down to the physical value of the pion mass and even below, these calculations allow a detailed comparison with the predictions of SU(2) chiral perturbation theory and a determination of some of its low energy constants. Finally, I will present an update on our strategy to compute the leading-order hadronic contribution to $g_\mu-2$

10/30/2014

In this talk we discuss the BFKL equation in the non-abelian gauge theory with the Higgs mechanism of the mass generation. We view this equation as a model for the correct large-$b$ behaviour of the scattering amplitude at high energy.  We found that the spectrum of the massive BFKL Pomeron coincides with the spectrum of the massless BFKL equation for all $\omega$'s and propose a simple approximation for the eigenfunction of the massive BFKL equation. We calculated that the slope of the trajectory is not generated in the massive BFKL equation. Hence we can state that the correct behaviour at large $b$ does not influence the main properties of the BFKL equation.

10/16/2014

Expectation values of bare operators computed using lattice techniques require renormalization before they can be compared with real world data. In today's calculations the renormalization constants are usually evaluated on the lattice, i.e. they are computed non-perturbatively. In this talk I will present a non-perturbative renormalization scheme based on correlation functions of desired operators in position space. I will discuss the cases of renormalization factors of fermion bilinears and show that this scheme can be used to calculate non-perturbatively their running.

10/2/2014

Stefan Meinel (University of Arizona/RBRC)

Baryons containing charm or bottom quarks are interesting systems in QCD because their dynamics is constrained by approximate heavy-quark symmetries. Furthermore, weak decays of heavy baryons play an increasingly important role for flavor physics at the LHC. I will give an introduction to the fascinating world of heavy baryons, and present recent lattice QCD results for their spectrum, strong decays widths, and weak decay form factors.

09/11/2014 (Large Seminar Room)

What causes the QGP to become the sQQGP?

Chris Korthals Altes (NIKHEF & Centre Physique Theorique au CNRS)

When going down from asymptotic temperatures the QGP converts into a  strongly interacting plasma. What are the excitations that cause this to happen? From the lattice we get
intriguing suggestions, but these are hard to make quantitative. Effective potentials describe accurately  bulk properties but do not answer the question.
In this talk I want to discuss the role that calorons may play. These are thermal instantons, and their contribution to the pressure and the effective potential can be computed. We show an amusing analytic result that replaces the old, partly numerical result of Gross-Pisarski-Yaffe.

08/28/2014

Shoichiro Tsutsui (Kyoto University)

In the early stage of heavy-ion collisions, strong longitudinally polarized color-electromagnetic fields are produced. We investigate parametric instabilities of classical Yang-Mills fields in a wide momentum range under a time-dependent and spatially homogeneous color-magnetic field in a non-expanding geometry. Parametric resonance in colored plasmas is firstly discussed by Berges, Scheffler, Schlichting and Sexty (BSSS). Their analysis performed by the classical statistical simulation suggests that lower momentum modes become unstable and its behavior is similar to Nielsen-Olesen instabillity.

We worked out to analyze the stability of fluctuations around BSSS configuration systematically based on the Floquet theory. We get the complete structure of instability bands on the (p_z, p_T) plane. We find that the origin of all these instabilities considered here should be regarded as the result of parametric resonance and it is completely different from Nielsen-Olesen instability.

08/14/2014

I will first discuss about photon propagations in strong magnetic fields, where refractive indices deviate from unity and become complex values without any matter effect. I will then proceed to charmonium spectroscopy in magnetic fields by QCD sum rules and give some prospects in application to light and charged mesons.

08/07/2014

We study fluctuation effects on QCD phase diagram in the strong coupling lattice QCD (SC-LQCD) based on auxiliary field Monte-Carlo (AFMC) method. In the strong coupling limit, we have found that fluctuation effects alter the boundary of  chiral phase transition compared with the mean field analysis in two numerical methods, auxiliary field Monte-Carlo (AFMC) method [1] and monomer-dimer-polymer simulation [2]. The strong coupling limit, however, is the opposite limit in comparison with the continuum limit, so evaluating finite coupling effects with fluctuations is required to obtain the insight into continuum QCD phase diagram [3].

In my presentation, I will construct an effective action in the strong coupling limit and show resultant QCD phase diagram.
Next, I will give a method to include both fluctuation and finite coupling effects via sequential bosonization procedure in AFMC
and show new results. I will also discuss the origin of the sign problem in AFMC.

[1] T. Ichihara, A. Ohnishi, T. Z. Nakano, arXiv:1401.4647 [hep-lat]. [2] W. Unger, P. de Forcrand, J. Phys. G38 (2011) 124190. [3] K. Miura, T. Z. Nakano, A. Ohnishi and N. Kawamoto, Phys. Rev. D 80, 074034 (2009) [arXiv:0907.4245 [heplat]].

07/03/2014

I will show the derivation, of an effective Polyakov loop theory with heavy quarks on the lattice for two-color QCD. I compare the model to a simpler Polyakov loop theory and with data from full two-color QCD simulations around and above the critical Temperature. I then apply the effective theory at finite temperature and density to extract quantities like Polyakov loop correlators, effective Polyakov loop potentials, and baryon density. In the cold and dense regime, the theory shows the Silverblaze property and signs of a  possible Bose-Einstein condensation of diquarks.

06/05/2014

05/29/2014

Proton structure functions are currently described with excellent accuracy in terms of parton distribution functions,   defined in terms of  collinear factorization and DGLAP evolution. With decreasing  x however, parton densities increase  and are ultimately expected to saturate. In this regime DGLAP evolution is expected to break  down  and non-linear evolution equations will take over.  In this talk I will  present recent result on an implementation of physical DGLAP  evolution. Unlike the conventional description in terms of parton distribution functions, the former describes directly the Q dependence of the  measured structure functions and is therefore insensitive to factorization scheme and scale ambiguities. As a consequence it provides a more stringent test of DGLAP evolution and eases the manifestation of (non-linear) small x  effects.

05/15/2014

The axial charge dynamics is an interesting subject in both electroweak theory and QCD. In electroweak theory, it is closely related to baryon number violation. In QCD, it is a key component in anomaly induced phenomena such as chiral magnetic effect and chiral vortical effect. In this talk, I will begin by reviewing the status of axial charge dynamics at weakly coupled gauge theory, and discussing the subtlety in the operator relation of anomaly. Then I will consider a holographic model at strong coupling, which enables us to access directly the correlators of axial charge and topological charge density. Finally I will show the full dynamics of axial charge in the model.

I will show that the acoustic scaling patterns of anisotropic flow for different event shapes at a fixed collision centrality (shape-engineered events), provide robust constraints for the event-by-event fluctuations in the initial-state density distribution from ultrarelativistic heavy ion collisions. The empirical scaling parameters also provide a dual-path method for studying the the temperature and baryon chemical potential (T, \mu_B) dependence of the specific shear viscosity (eta/s) of the quark-gluon plasma (QGP) produced in these collisions.  An initial calibration of the scaling parameters via detailed viscous hydrodynamical model calculations, gives robust eta/s estimates for the plasma produced in Au+Au  and Pb+Pb collisions at RHIC (Root_s =0.2 TeV) and the LHC (Root_s = 2.76 TeV) (respectively) which are insensitive to the initial-state geometry models considered.

I will discuss how multi-particle flow cumulants can help to distinguish between various models of p+A interactions.

03/27/2014

Yan-Qing Ma (BNL)

Based on QCD factorization, (some) experimentally measurable differential cross sections can be factorized into perturbatively calculable hard parts convoluted with a set of nonperturbative but process-independent Parton Distribution Functions (PDFs). However, the choice of PDFs is not unique. There could be, in principle, many sets of equally good PDFs to factorize the measured cross sections. Different sets of PDFs could be related to each other by a convolution equation with perturbatively calculable matching kernels in powers of $\alpha_s$. As a special case, we show that there is a set of "quasi PDFs" that could be evaluated on an Euclidean Lattice. We calculate the perturbative kernels to match this set of "quasi PDFs" to the standard collinear PDFs to the first nontrivial order. With these matching kernels, we could extract standard PDFs from lattice QCD calculations directly.

03/20/2014

Matt Sievert (Ohio State University)

We study the origin of the Sivers function in the quasi-classical limit (McLerran-Venugopalan model), applicable when the density of color charges is large. The classical limit can be achieved by a heavy nucleus, which already possesses a large number of color charges in its rest frame, or by boosting any hadron to sufficiently high energy that gluon bremsstrahlung drives up the charge density. The large charge density in the classical limit allows us to resum multiple rescatterings and permits a mean-field description, such as a hadron made up of a large number of independent low-$x$ partons. This allows us to decompose the TMD's of the hadron in terms of the TMD's of its partons, the Wigner distributions of the partons within the hadron, and Wilson lines due to multiple rescattering. We find that the Sivers function of the hadron receives one contribution that simply aggregates the Sivers functions of the partons, and another due to the combination of orbital angular momentum and screening due to multiple rescattering. This channel is fundamentally different from the known “lensing mechanism,” and it provides a simple interpretation for the process dependence of the Sivers function. This method can be readily extended to study other TMD's and to include quantum evolution.

03/06/2014

Strongly correlated fermionic system is one of the important topic in condensed matter physics, and appears in various contexts. Since important physical contributions drastically changes by energy scales, it provides rich examples of phase transitions and of crossovers. In order for unbiased and systematic studies of many-body fermions, we review aspects of fermionic functional renormalization group (f-FRG). We mainly discuss its application to ultracold atomic gases, and show how it describes the BCS-BEC crossover.

02/27/2014

Daniel Pitonyak (RBRC)

The measurement of transverse single-spin asymmetries (TSSAs) in proton-proton collisions has been one of the main focuses of the RHIC spin program.  Large effects have been seen, yet issues still remain on the theoretical side.  Namely, the assumption that the so-called Qiu-Sterman distribution function dominates the observable has led to a "sign mismatch" with the so-called Sivers function that arises in TSSAs in semi-inclusive deep-inelastic scattering.  This disagreement is really an indication that we still do not fully understand what causes TSSAs in proton-proton collisions, which is truly a "spin crisis".  Speculation in recent years is that significant contributions arise from the fragmentation side of the process.  In this talk I will review the current theoretical formalism for this observable and explore the role that fragmentation can play in the reaction.

02/06/2014

Kouji Kashiwa (RBRC)

In this talk, I will present a recent progress of the investigation of the QCD phase structure by using the imaginary chemical potential and effective models of QCD. At finite imaginary chemical potential, QCD has several characteristic properties such as the Roberge-Weiss periodicity and transition. These properties are quite important to construct and/or extend the effective model. Moreover, the imaginary chemical potential can be converted to the temporal fermion boundary condition and thus its knowledge may be useful when we investigate the Hosotani mechanism in QCD-like gauge theory where the fermion boundary condition plays a crucial role.

01/16/2014

Turbulent thermalization process in heavy-ion collisions at ultrarelativistic energies

Soeren Schlichting (BNL)

In this talk I will discuss the thermalization process in non-Abelian gauge theories within a weak-coupling approach. We employ classical-statistical real-time lattice simulations as a first-principle approach, and compare our findings with kinetic theory considerations. Most remarkably, we find that the thermalization process of the longitudinally expanding plasma is governed by a universal attractor. At late times the system exhibits the self-similar dynamics characteristic of wave turbulence, irrespective of the underlying initial conditions.

01/09/2014

Physics near the conformal boundary in SU(3) gauge theory

Yasumichi Aoki (KMI, Nagoya University)

Through the composite spectrum of the mass-deformed theory on the lattice, we investigate the physics near the lower edge of the conformal window in SU(3) gauge theory with N_f fundamental fermions. A possible candidate is found for the walking technicolor theory, which shows consistency with the slowly running coupling, spontaneous chiral symmetry breaking, and large mass anomalous dimension, the properties for the successful technicolor theory to replace the Higgs sector of the standard model. The flavor singlet scalar spectrum is investigated for the test whether the 125 GeV Higgs could be accommodated in the theory.

12/12/2013

Composite Bosonic Dark Matter

Ethan Neil (University of Colorado / RBRC)

We present results for the large-$N$ limit of the (1+1)-dimensional principal chiral sigma model. This is an asymptotically-free $N\times N$ matrix-valued field with massive excitations. All the form factors and the exact correlation functions of the Noether-current operator and the energy-momentum tensor are found, from Smirnov's form-factor axioms. We consider (2+1)-dimensional $SU(\infty)$ Yang-Mills theory as an array of principal chiral models with a current-current interaction. We discuss how to use our new form factors to calculate physical quantities in this gauge theory.

11/07/2013

Baryon number distribution in lattice QCD simulations

Keitaro Nagata (KEK)

Baryon number distribution and its cumulants have attracted recent interest in the study of a critical endpoint on the QCD phase diagram.

We study the baryon number distribution at finite temperature and density using lattice QCD simulations. We employ a canonical formalism to calculate not only cumulants but also the baryon number distribution. We also apply the canonical formalism to a Lee-Yang zero analysis, where Lee-Yang zeros are obtained as roots of a fugacity polynomial.

We present results obtained using lattice QCD simulations with two-flavor clover-Wilson fermions for lattice size 8^3x4 and 10^3x4, m_ps/m_V = 0.8.

10/24/2013

Strongly coupled gauge theories in and out of the conformal window

Anna Hasenfratz (University of Colorado)

Asymptotically free gauge systems with many fermionic degrees of freedom can develop a conformal infrared fixed point. Near the conformal window these strongly coupled systems can have unusual properties, and might contain a light scalar, a composite candidate for the Higgs boson.

Lattice studies are particularly suited to study these strongly coupled models, though methods developed for QCD studies are not always effective. In this talk I will give a brief overview of our understanding of these  systems. I will concentrate on two rather different methods, the Dirac operator spectral density, and a variant of  finite size scaling, to illustrate the unusual properties of these intriguing systems.

10/17/2013

Application of the twist-3 framework to the high energy spin physics

Shinsuke Yoshida (Nishina Center, RIKEN)

High energy hadron scattering is a powerful tool to investigate the internal structure of the hadrons. The perturbative QCD analysis have been successful in giving the quantitative description for many high energy processes and the knowledge of hadron structure based on the first principle. Recently some observables have shown the apparent disagreement with the conventional pQCD calculation. These novel observables have received much attention in recent decades and many theoretical works were proposed to solve the problems. In this talk, I introduce the twist-3 mechanism as the recent important progress of pQCD analysis. I especially discuss the application of the framework to the two unsolved problems, the single spin asymmetry and the proton spin problem.

10/10/2013

Non-equilibrium collective dynamics in high-energy heavy ion collision

Akihiko Monnai (RIKEN BNL)

The collider experiments at RHIC and LHC have shown the quark-gluon matter around the crossover temperature has unique properties including near perfect fluidity. I will cover several topics related to non-equilibrium dynamics for the strongly-coupled quark gluon plasma.

10/03/2013

(Qusai) Nambu-Goldstone Fermion in QGP and Cold Atom System

Daisuke Satow (RIKEN / BNL)

It was suggested that supersymmetry (SUSY) is broken at finite temperature, and as a result, a Nambu-Goldstone fermion (goldstino) related to SUSY appears. Since dispersion relations of quarks and gluons are almost degenerate at extremely high temperature, quasi-zero energy quark excitation was suggested to exist though QCD does not have exact SUSY. As for the condensed matter system, a setup of cold atom system in which the Hamiltonian has SUSY was proposed, the goldstino was suggested to exist, and the dispersion relation of that mode at zero temperature was obtained recently.

09/26/2013

Yu Maezawa (BNL)

We study spatial meson correlators and screening properties at finite temperature in 2+1 flavor QCD using the Highly Improved Staggered Quarks (HISQ) action. The Screening masses are obtained from spatial meson propagators and enable us to probe the sensitivity of hadronic correlation functions to the quark structure in thermal matter. We focus on the thermal strange and charmed flavor sectors and calculate the meson screening masses on lattices with a temperature range of 140--740 MeV. We find that significant modifications of thermal masses in the strangeness appear even below the critical temperature (Tc), whereas for charmonium states modifications become significant only for T > 1.2Tc. We also present several other properties of meson states at finite temperature, e.g. modifications of amplitudes and the onset of spin and parity degeneracy at high temperature.

07/25/2013

Out of equilibrium chiral magnetic conductivity and chiral magnetic wave

Shu Lin (RIKEN BNL)

Chiral anomaly manifests itself as chiral magnetic effect and chiral separation effect in the presence of background magnetic field. In a finite temperature medium, these effects turn charge diffusion wave into chiral magnetic wave. Both chiral magnetic effect and chiral magnetic wave can lead to direct and indirect signatures in heavy ion collisions experiment. In reality, magnetic field exists only at early stage of collisions, when medium is not fully thermalized. We investigate the modification of chiral magnetic effect and chiral magnetic wave in a thermalizing medium using a holographic model and discuss implications to heavy ion phenomenology.

07/18/2013

Heavy-quarkonium theory in the LHC era

Bernd Kniehl (University of Hamburg)

We review the present landscape of heavy-quarkonium theory, its tests by worldwide collider and fixed-target experiments, and the future perspectives offered by the LHC. Special emphasis is placed on the effective quantum field theory of nonrelativistic QCD (NRQCD), endowed with the factorization theorem conjectured by Bodwin, Braaten, and Lepage, which arguably constitutes the most probable candidate theory at the present time. Being impressively consolidated at the next-to-leading order (NLO) by the world's data on unpolarized J/psi production, NRQCD factorization has now reached the crossroads. In fact, NLO NRQCD exhibits encouraging agreement with the first J/psi polarization measurement at the CERN LHC, performed by ALICE at 7 TeV, while it severely disagrees, by 10-20 experimental standard deviations, with a similar measurement by CDF at Tevatron's Run II, with 1.96 TeV. In this tantalizing situation, we eagerly await final clarification by the wealth of LHC data to come.

06/27/2013

Masaru Hongo (University of Tokyo)

Anomaly induced transport effects, like the Chiral Magnetic Effect or the Chiral Separation Effect, have recently attracted much attention and are expected to be observed in ultra-relativistic heavy-ion collisions. However, the evidence in the experiments has been elusive, mainly due to the lack of quantitative theoretical predictions. In order to asses the contributions from anomalous transport in heavy-ion collisions, we consider a hydrodynamic model in the presence of anomaly. We numerically solve the anomalous hydrodynamic equations under a background electromagnetic field and calculate the propagation of the chiral magnetic wave in an expanding quark-gluon plasma. The charge-dependent elliptic flow ($v_2^{\pm}$ is recently proposed as a signal of the chiral magnetic effect. We calculate the charge-dependent particle distributions and estimate the contribution from anomaly to $v_2^{\pm}$.

06/20/2013

Hong Zhang (Stony Brook University)

From Tevatron and LHC data, it is clear that the non-relativistic QCD (NRQCD) model for heavy quarkonium production, which is the most popular one at present, is not able to explain the polarization of produced heavy quarkonia at high transverse momentum pT.
A new approach to evaluate heavy quarkonium production, expanding the cross section in powers of 1/pT before the expansion in powers of alpha_s, was proposed recently.  In terms of perturbative QCD (pQCD) factorization, it is proved that both the leading and next-to-leading power terms in 1/pT for the cross sections can be systematically factorized to all orders in powers of alpha_s.  The predictive power of this new pQCD factorization formalism depends on several unknown but universal fragmentation functions (FFs). With new QCD evolution equations for FFs, one only needs to determine these FFs at an initial scale of the order of heavy quarkonium mass.  In this talk, I will introduce the framework of the new factorization method and discuss the determination of FFs, in particular, a NRQCD model calculation of these FFs at the initial scale, and comment on the impact on the quarkonium polarization.

05/30/2013

Review of the Planck results by an inflationary physicist

Fedor Bezrukov (UCONN/RBRC)

I will review the results from the Planck mission.  In short, they confirmed with significant precision the current standard cosmological model, LambdaCDM.  I will comment on the meaning of the results for the inflationary models, what is still unknown, and what can be learned in near future.

05/23/2013

Hyung-Jin Kim (BNL)

05/02/2013

Chen Chen (Rensselaer Polytechnic Institute)

An approach to the formulation of chiral gauge theories on the lattice is to start with a vector- like theory, but decouple one chirality (the "mirror" fermions) using strong Yukawa interactions with a chirally coupled "Higgs" field. While this is an attractive idea, its viability needs to be tested with nonperturbative studies. The model that we studied here, the so- called "3-4-5" model, is anomaly free and the presence of massless states in the mirror sector is not required by anomaly matching arguments, in contrast to the "1-0" model that was studied previously. I will talk about the results we got from the study of the “3-4-5” model, which does not suggest the decoupling of the mirror fermions and therefore no emergence of the chiral gauge theory.

04/25/2013

Benjamin Doyon (King's College)

04/18/2013

Study of the magnetic properties of hadrons can be achieved by including external magnetic fields in lattice QCD computations. This approach should prove particularly useful for studying magnetic moments of light nuclei, and the magnetic polarizabilities of hadrons. I present a simple idea necessary to make the approach practicable for charged hadrons.

I briefly report on the current status of QCD phase diagram at vanishing baryon density. I focus on the QCD phase diagram with Nf=3 and 2+1 using Highly Improved Staggered Quarks on $N_{\tau}=6$ lattices. The nature of the QCD chiral phase transition by approaching towards the chiral limit of light quark mass is investigated. The influence of the chiral phase transition at vanishing baryon density to the real world is also discussed.

03/28/2013

The neutral pion decay and the chiral anomaly on the lattice

Xu Feng (KEK)

We perform a nonperturbative calculation of the pion-to-two-photon transition form factor and the associated decay width using lattice QCD. The amplitude for a two-photon final state, which is not an eigenstate of QCD, is extracted through a Euclidean time integral of the relevant three-point function. We utilize the all-to-all quark propagator technique to carry out this integration. We execute the calculation using the overlap fermion formulation, which ensures the exact chiral symmetry on the lattice and produces the chiral anomaly through the Jacobian of the chiral transformation. We calculate the form factor and decay width with a comprehensive estimate of various systematic errors, except for a possible discretization effect. Our results reproduce the predication of the ABJ anomaly in the chiral limit and also agree with the PrimEx experimental measurement at the physical pion mass.

03/07/2013

Radoslaw Kycia (Cracow University of Technology)

Nonlinear PDEs are basic tools for modeling many physical, biological and chemical phenomenons. Many of them admit a scaling symmetry which leads to universal behavior in some limits. The prominent example of usefulness of the scaling reasoning is the Taylor's estimation of the energy of nuclear explosion form a few pictures of the blast. The scaling plays extremely important role also in smilinear wave equations with power type nonlinearity - the main subject of this talk. These equations are one of the simplest, yet they are still in the mainstream of mathematical and numerical investigations. After a short description of classical results on non-global existence for various nonlinear PDEs, I will show blowup occurrence for the solutions of these equations for different space dimensions and values of the power exponents. The existence of intermediate attractors and the behavior of a solution around them will also be presented. The talk will be on the classical level, however, some hints on the influence of quantum effects on the evolution will also be outlined.

02/28/2013

Tatsuhiro Misumi (BNL)

02/21/2013

Matthias Kaminski (University of Washington)

Over the past years an exciting new research area has emerged in Physics. It brings together physicists studying string theory, nuclear theory, heavy ion collisions, condensed matter systems, and many more. What unifies all of these subjects is the question: how do systems behave at strong coupling? The connection between these different subjects is provided by a particular holographic correspondence in combination with effective field theories. In this talk I will give an intuitive introduction to the fascinating concepts of this thriving research area. In particular we will work out the example of the chiral vortical effect in heavy ion collisions, discussing relativistic hydrodynamics as well as far-from-equilibrium settings.

02/07/2013

Etsuko Itou (KEK)

01/17/2013

Lea Ferreira dos Santos (Yeshiva University)

In this talk, I will discuss the crossover from integrability to chaos and the viability of thermalization in isolated quantum many-body systems. The relaxation process after a quench can be very similar in both domains, but thermal equilibrium can be reached only when the system is chaotic. The proper entropy to describe the system out of equilibrium is the so-called diagonal entropy, which depends only on the diagonal elements of the system’s density matrix in the energy representation. When thermal equilibrium is reached, the diagonal entropy is shown to coincide with the thermodynamic entropy. The diagonal entropy allows also for a better understanding of the notion of typicality in finite systems.

01/10/2013

Daniel Pitonyak  (Temple University)

12/20/2012

11/01/2012

Non abelian anyons and the art of computing with knots

Giuseppe Mussardo (SISSA, Trieste)

The main topic of the seminar is the theory of non-abelian anyons, that is at the root of topological quantum computation. The exotic statistical properties of such excitations make it possible to set up quantum computational schemes based on robust topological properties as those of knots and braids. In particular I will discuss how to set up an efficient algorithm for realizing the building logic gates of a quantum computer using the icosahedral group.

09/20/2012

Li Yan (Stony Brook)

Abstract: We develop non-linear flow response formalism for hydrodynamics, as an extension of the well-known linear flow response assumption. In addition to characterizing initial state fluctuations with cumulant definitions, the essential ingredients of this formalism is the determination of a set of non-linear response coefficients by single-shot hydrodynamics, and especially their dependence on centrality and viscosity. As an application, we predict the recently measured reaction plane correlations, and compare our results with the experiment and event-by-event hydrodynamical simulations. We find that the observed behavior of the correlations are largely determined by the competition between linear and non-linear flow generation.

09/13/2012

09/06/2012

Tatsuhiro Misumi (BNL)

08/30/2012

Kazuhiro Watanabe (The University of Tokyo)

08/23/2012
Robert Lang (Technical University Munich)

Matthias Drews (Technical University Munich)

08/16/2012
Fedor Bezrukov (University of Connecticut / RBRC)

Abstract: The Higgs boson with the mass recently announced by the LHC experiments corresponds within current precision to the boundary value between the situations when the electroweak vacuum is stable and metastable.  I will discuss the latest developments in the calculation of this boundary mass and importance of measurement of other SM parameters (top quark mass and the strong coupling constant).  I will also discuss what is the meaning of this boundary value in various minimal modifications of the Standard Model.

Kirill Tuchin (Iowa State University)

07/26/2012

Jinfeng Liao (Indiana University / RBRC)

07/12/2012

Shu Lin (RBRC)

Abstract: Thermalization of strongly coupled gauge theory can be described by a gravitational collapse process via gauge/gravity duality. We studied the evolution of unequal time correlator in a gravitational collapse background, which allowed us to probe different stages of thermalization process. We found that the singularities of the correlator are consistent with geometric optics picture in the gravitational collapse background. We found the thermalization is characterized by the disappearance of singularities on real time axis and possible emergence of singularities in complex time plane in the correlator.

06/21/2012

Critical endpoint for deconfinement in matrix and other effective models

Koji Kashiwa (RBRC)

06/07/2012

Nucleon structure from 2+1-flavor dynamical DWF QCD at nearly physical pion mass

Shigemi Ohta (KEK/RBRC)

Abstract: I report the current status of joint RBC+UKQCD numerical lattice QCD study of nucleon structure using several 2+1-flavor dynamical domain-wall fermions (DWF) ensembles with pion mass as low as 170 MeV and spatial volume as large as $$L=4.6$$ fm across.  Isovector form factors of vector and axialvector currents and some low moments of isovector structure functions will be discussed. In particular the results for the ratio of vector and axial charges, gA/gV, calculated at pion mass of about $$m_\pi=250$$ MeV seems to confirm our earlier conjecture that the quantity scales with a parameter $$m_\pi L$$.

05/31/2012

Elina Seel (University of
Frankfurt)

05/24/2012

The transition temperature in QCD

Alexei Bazavov (BNL)

Kimmo Tuominen (University of Jyvaskyla & Helsinki Institute of Physics)

Larry McLerran (BNL)

Abstract: I argue that in electroweak theory, an electroweak axion has the right energy density to correspond to the dark energy.  This electroweak axion is the Goldstone boson of B+L symmetry, in the absence of instantons. Instantons generate an axion mass.The resulting axion has a mass of the order the inverse size of the universe. The dark energy is associated with the axion field energy. This result  assumes no new physics up to of order the Planck scale.

04/26/2012

Eigo Shintani (RBRC)

04/05/2012

A saga of the weak and the strong: hadronic parity violation

Brian Tiburzi (CCNY/RBRC)

03/29/2012

Holographic Fermi surfaces

David Vegh (Stony Brook)

03/15/2012

The Spin of Holographic Electrons at Nonzero Temperature and Density

Christopher Herzog (YITP of Stony Brook)

03/08/2012

Baryon number probability distribution near a phase transition

Kenji Morita (YITP of Kyoto University)

Abstract: I discuss the baryon number probability distribution at finite temperature and chemical potential. Starting from a model thermodynamic potential which has divergent kurtosis at the phase transition, I show how to calculate the probability distribution and its relation to the analytic structure of the thermodynamic potential at complex chemical potential.

03/01/2012

KNO scaling of fluctuations in pp and pA, and higher-order eccentricities in heavy-ion collisions

02/23/2012

Jet Fragmentation From Two Dimensional Field Theory

Frasher Loshaj (Stony Brook)

Abstract: We consider QED_2 (Schwinger Model) as a toy model for studying jet fragmentation in both vacuum and medium. Using the bosonized version of the model, we calculate the fragmentation function of jets in e^+e^- annihilation and find reasonable agreement with the data. We then apply the model to jet quenching in heavy ion collisions, and address the jet fragmentation scaling observed recently at the LHC.

02/09/2012

Direct photon physics in heavy ion collisions: Current status and Future

Takao Sakaguchi (BNL)

Abstract: Direct photons are a promising probe to directly explore the partonic system which are not possible by hadronic probes that are often distorted in the hadronization process. The PHENIX experiments at RHIC measured high pT photons coming from initial hard scattering process in heavy ion collisions for the first time and published in 2005. Then, recently, the experiment came up with low pT photon results, supposedly coming from the hot partonic matter. These measurements characterized the initial state and partonic matter state, but there are states after the collisions yet to be investigated.

I will present on the recent results on direct photons from the PHENIX experiments, and then discuss what we can explore with direct photon measurement in the future RHIC runs.

02/02/2012

Instantons and sphalerons in magnetic field

Gokce Basar (Stony Brook)

Abstract: We study the properties of the Euclidean Dirac equation for a light fermion in the presence of both a constant abelian magnetic field and an SU(2) instanton. In particular, we analyze the zero modes analytically in various limits, both on R^4 and on the four-torus, in order to compare with recent lattice QCD results, and study the implications for the electric dipole moment. We also present a holographic computation of the sphaleron rate in a medium with constant magnetic flux. We show that in the strong field limit, the rate has a linear dependence in B.

01/12/2012

Ions in biology: Water and Proteins

Purushottam Dixit (BNL)

Abstract: The milieu of all biological activity is a complex electrolyte solution wherein inorganic ions play an important role. Classical electrolyte theory explains some of the activity of ionic species yet more interesting phenomena in biology such as the electrical activity of the heart and firing of neurons rely on the specific chemistry of the ions. We need a statistical mechanical theory to separately understand the role of physics and chemistry in the interaction of ions with biomaterials.

The excess free energy of ion hydration/binding  contains all the information about the behavior of a given ion in solution. We develop a physically motivated framework to interrogate the different contributors to the excess free energy of an ion. We then apply the framework to the study of Na+(aq). We present a possible explanation for the disparate reports of experimentally determined coordination numbers for Na+(aq). We then apply the same framework and provide an explanation for the long standing puzzle of K+ over Na+ selectivity of the KcsA K+ channel, a membrane protein that excludes the smaller Na+ from the ionic current across neurons while allowing the larger K+ to pass.

12/08/2011

Understanding the heavy quarkonia production at hadron colliders within NRQCD factorization

Yan-Qing Ma (BNL)

12/01/2011

Anomaly-induced charges in nucleons

Yu Maezawa (BNL)

11/17/2011

Factorization with transverse momentum dependent parton distribution functions

Ted Rogers (Stony Brook)

11/10/2011

Exploring dynamical QED effects with the reweighting method

Tomomi Ishikawa (RBRC)

11/03/2011

Probing QCD phase diagram with charge fluctuations

10/27/2011

Calculating the incoherent and total cross-sections in exclusive diffractive vector meson production in eA

Tobias Toll (BNL)

10/21/2011

Relativistic Theory of Hydrodynamic Fluctuations

Joseph Kapusta (University of Minnesota)

Abstract: Hydrodynamic fluctuations have been applied to a wide variety of physical, chemical, and biological phenomena in the past decade. In the context of high energy heavy ion collisions, there will be intrinsic fluctuations due to the finite size and finite particle content even if the initial conditions are fixed. Here we develop the theory of relativistic fluctuations, and apply it to a 1+1 dimensional boost invariant model. In analogy to the cosmic microwave background radiation, fluctuations might provide information on the equation of state, including a possible critical point, and on the transport coefficients.

10/13/2011

Symmetric forward-backward correlations as seen at RHIC

09/29/2011

Interaction of non-Abelian vortices with quasiparticles in high density QCD

Yuji Hirono (University of Tokyo)

09/22/2011

Exploring real-time functions on the lattice with inverse propagator and self-energy

Masakiyo Kitazawa (Osaka University)

09/15/2011

Transverse Spin and Transverse Structure of the Nucleon

Jian-ping Chen (Jefferson Lab)

Abstract: Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions (PDFs) in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction (QCD). The transverse spin structure and the TMDs have been the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has been part of the exploration of this effort. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space. Combining with the world data, the transverse spin (transversity) in the valence quark region will be extracted with a good precision and the u and d quark tensor charges of the nucleon will be determined. The precision information on TMDs will also allow a detailed study of the quark orbital motion and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will greatly expand the kinematical reach to allow a precision study of the TMDs of the sea quarks and gluons, in addition to completing the study in the valence region.

08/18/2011

Nucleon structure from 2+1-flavor dynamical DWF lattice QCD at nearly physical pion mass

Shigemi Ohta (RBRC)

01/20/2011

Estimating thermal dilepton rates and electrical conductivity in quenched QCD

Heng-Tong Ding (BNL)