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.
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: Tomomi Ishikawa (Room 2-49), Daniel Pitonyak (Room 2-52)
02/12/2015Jinfeng Liao (Indiana University / RBRC) 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. 01/15/2015The 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). 12/18/2014Hans-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. 12/11/2014One 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. 12/04/2014In 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. 11/20/2014Jacquelyn 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 $g_\mu-2$ 10/30/2014Eugene Levin (Tel Aviv University and UTFSM) 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. 10/16/2014Expectation 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. 08/28/2014In 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. 08/14/2014Koichi Hattori (RIKEN/RBRC) 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. 08/07/2014Terukazu Ichihara (Kyoto University) 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]]. 07/03/2014I 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. 06/05/2014Naoto Tanji (RIKEN/BNL) 05/29/2014Martin Hentschinski (BNL) 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. 05/15/2014The 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. 04/24/2014Roy Lacey (Stony Brook University) 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. 03/27/2014Yan-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. 03/20/2014We 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.
02/27/2014Daniel 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. 02/06/2014Kouji 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.
01/30/2014Hiroshi Ono (BNL) 01/16/2014Soeren 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. 01/09/2014Yasumichi 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.
11/21/2013Axel Cortes Cubero (CUNY) 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.
11/14/2013Shigemi Ohta (KEK/RBRC) 11/07/2013Keitaro Nagata (KEK) Baryon number distribution and its cumulants have attracted recent interest in the study of a critical endpoint on the QCD phase diagram.
10/24/2013Anna 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.
10/17/2013Shinsuke 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. 10/10/2013Non-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 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.
07/25/2013Out of equilibrium chiral magnetic conductivity and chiral magnetic wave
Shu Lin (RIKEN BNL)
07/18/2013Heavy-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 $v_2^{\pm}$.
06/20/2013Hong 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. 05/30/2013Review 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.
05/02/2013Chen 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.
04/25/2013Benjamin Doyon (King's College)
04/18/2013Study 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.
04/04/2013Heng-Tong Ding (BNL)
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.
03/28/2013Xu 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.
03/14/2013
Eiji Nakano (Kochi University)
03/07/2013Radoslaw 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)
01/17/2013Lea 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.
01/10/2013Daniel Pitonyak (Temple University)
12/20/2012Jacqueline Bonnet (University of Giessen)
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.
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.
Tatsuhiro Misumi (BNL)
08/30/2012
Kazuhiro Watanabe (The University of Tokyo)
08/23/2012Robert Lang (Technical University Munich)
Matthias Drews (Technical University Munich)
08/16/2012Fedor 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.
07/26/2012
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.
06/21/2012Critical endpoint for deconfinement in matrix and other effective models
Koji Kashiwa (RBRC)
Nucleon structure from 2+1-flavor dynamical DWF QCD at nearly physical pion mass06/07/2012
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
Two-flavor linear sigma model in presence of axial anomaly from Functional Renormalization Group
The thermodynamics of the 2-dimensional O(N) modelMara Grahl (University of Frankfurt)
Elina Seel (University of
Frankfurt)
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.
04/26/2012Eigo Shintani (RBRC)
04/05/2012A saga of the weak and the strong: hadronic parity violation Brian Tiburzi (CCNY/RBRC) 03/29/2012Holographic 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) 03/08/2012Baryon 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. 03/01/2012KNO scaling of fluctuations in pp and pA, and higher-order eccentricities in heavy-ion collisions Adrian Dumitru (CUNY/RBRC) 02/23/2012Jet 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. 02/09/2012Direct 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. 02/02/2012Instantons 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. 01/12/2012Ions 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. 12/08/2011Understanding the heavy quarkonia production at hadron colliders within NRQCD factorization Yan-Qing Ma (BNL) 12/01/2011Anomaly-induced charges in nucleons Yu Maezawa (BNL) 11/17/2011Factorization with transverse momentum dependent parton distribution functions Ted Rogers (Stony Brook) 11/10/2011Exploring dynamical QED effects with the reweighting method Tomomi Ishikawa (RBRC) 11/03/2011Probing QCD phase diagram with charge fluctuations Vladimir Skokov (BNL) 10/27/2011Calculating the incoherent and total cross-sections in exclusive diffractive vector meson production in eA Tobias Toll (BNL) 10/21/2011Relativistic 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. 10/13/2011Symmetric forward-backward correlations as seen at RHIC Adam Bzdak (RBRC) 09/29/2011Interaction of non-Abelian vortices with quasiparticles in high density QCD Yuji Hirono (University of Tokyo) 09/22/2011Exploring real-time functions on the lattice with inverse propagator and self-energy Masakiyo Kitazawa (Osaka University) 09/15/2011Transverse 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. 08/18/2011Nucleon structure from 2+1-flavor dynamical DWF lattice QCD at nearly physical pion mass Shigemi Ohta (RBRC) 01/20/2011Estimating thermal dilepton rates and electrical conductivity in quenched QCD Heng-Tong Ding (BNL) |