32nd International Symposium on Lattice Field Theory (Lattice 2014)

Session

Nonzero temperature and Density

1

23 Jun 2014, 14:15

Columbia University

Conveners

Nonzero temperature and Density: Parallel 1A

• Shinji Ejiri

Nonzero temperature and Density: Parallel 1E

• Christof Gattringer

Nonzero temperature and Density: Parallel 2A

• Ludmila Levkova

Nonzero temperature and Density: Parallel 2E

• Ion-Olimpiu Stamatescu

Nonzero temperature and Density: Parallel 3A

• Rajiv Gavai

Nonzero temperature and Density: Parallel 4A

• Christian Schmidt

Nonzero temperature and Density: Parallel 5A

• Urs Heller

Nonzero temperature and Density: Parallel 6A

• Heng-Tong Ding

Nonzero temperature and Density: Parallel 7A

• Szabolcs Borsanyi

Nonzero temperature and Density: Parallel 8A

• Tereza Mendes

Nonzero temperature and Density: Parallel 9A

• Gergely Endrodi

306. Chiral restoration and deconfinement in two-color QCD with two flavors of staggered quarks

Mr David Scheffler (TU Darmstadt)

23/06/2014, 14:15

Nonzero Temperature and Density

Talk

We study chiral restoration and deconfinement in two-color QCD with two flavors of staggered quarks using a RHMC algorithm on GPUs. We measure the chiral condensate and the corresponding chiral susceptibility over the lattice coupling across the finite temperature transition. Using Ferrenberg-Swendsen reweighting we extract the maxima of the chiral susceptibility in order to determine...

66. Curvature of the QCD critical line with 2+1 HISQ fermions

Dr Leonardo Cosmai (INFN)

23/06/2014, 14:15

Nonzero Temperature and Density

Talk

We present results on the curvature of the critical line of QCD with 2+1 HISQ fermions at nonzero temperature and quark density obtained by analytic continuation from imaginary chemical potentials. Monte Carlo simulations are performed by means of the MILC code suitably modified to include a nonzero imaginary baryon chemical potential. We set the chemical potential at the same value for the...

273. Effective SU(2) Polyakov Loop Theories with Heavy Quarks on the Lattice

Mr Philipp Scior (TU Darmstadt)

23/06/2014, 14:35

Nonzero Temperature and Density

Talk

We compare SU(2) Polyakov loop models with different actions with data from full two-color QCD simulations around and above the critical Temperature [1,2]. We then apply the effective theory at finite temperature and density to extract quantities like Polyakov loop correlators, effective Polyakov loop potentials and baryon density. [1] Smith et al. , Phys. Rev. D88 (2013) 054020 [2]...

296. The curvature of the QCD critical line from analytic continuation

Michele Mesiti (University of Pisa & INFN)

23/06/2014, 14:35

Nonzero Temperature and Density

Talk

We present preliminary results regarding the curvature of the critical line of N_f = 2+1 QCD with physical quark masses. We make use of the stout improved staggered fermions formulation, with a tree level improved Symanzik gauge action.

367. Phase diagram of QCD at finite isospin chemical potential with Wilson fermions

Prof. Chiho Nonaka (Nagoya University)

23/06/2014, 14:55

Nonzero Temperature and Density

Talk

We investigate the structure of the phase diagram of QCD at finite isospin chemical potential with Wilson fermions. From the behavior of meson correlators in temporal and spatial directions, Polyakov loop, isospin density and susceptibilities as a function of isospin chemical potential at zero and finite temperature, we extract the QCD phases at finite isospin chemical potential...

178. The effective Polyakov loop theory for finite temperature Yang-Mills theory and QCD

Dr Georg Bergner (ITP Goethe University Frankfurt)

23/06/2014, 14:55

Nonzero Temperature and Density

Talk

The effective Polyakov loop theory reproduces the main features of the Yang-Mills theory and QCD at finite temperature. A systematic derivation of the effective theory is a combined strong coupling and hopping parameter expansion. It includes a systematic ordering principle of the effective couplings. I will review this approach as well as results and possible applications. Furthermore, I...

290. Lattice simulations of G2-QCD at finite density I

Prof. Lorenz von Smekal (TU Darmstadt and JLU Giessen)

23/06/2014, 15:15

Nonzero Temperature and Density

Talk

In G2-QCD the SU(3) gauge group of QCD is replaced by the exceptional Lie group G2. This replacement leads to a theory that does not have a sign problem and can be simulated at finite baryon density using standard lattice techniques. The price to pay is that it contains bosonic as well as fermionic baryons. The physics of the light bosonic baryons is expected to be analogous to other QCD-like...

384. QCD with Wilson fermions and isospin chemical potential at finite and zero temperature

Mr Tobias Rindlisbacher (ETH Zurich)

23/06/2014, 15:15

Nonzero Temperature and Density

Talk

We study QCD with Wilson fermions in the presence of an isospin chemical potential mu_I. At zero temperature, condensation of iso-positive pions is expected to occur as soon as mu_I reaches half the pion mass. By looking at the isospin density and the mass spectrum of mesons as a function of mu_I, we investigate this pion condensation on the lattice and extend the study to non-zero...

279. Lattice simulations of G2-QCD at finite density II

Dr Bjoern Wellegehausen (JLU Giessen)

23/06/2014, 15:35

Nonzero Temperature and Density

Talk

G2-QCD is a QCD-like theory with fermionic baryons and fundamental quarks. Unlike QCD it does not suffer from a fermion sign problem at finite baryon density and therefore allows to investigate effects of fermionic baryons on the G2-QCD phase diagram with standard Monte-Carlo methods. In the talk we present recent results on the phase diagram at zero and non-zero temperature with an...

11. Status of the SU3 Lambda Scale

Prof. Bernd Berg (Florida State University)

23/06/2014, 15:35

Nonzero Temperature and Density

Talk

We compare the non-perturbative SU(3) lambada scale of Necco and Sommer with the lambda scale derived by Bazavov et al. from deconfining phase transition data of the Bielefeld group and others. Though the relative discrepancy is never larger than 2%, it matters in some applications. Differences are encountered between results from the set of smaller lattices of Necco and Sommer and ...

45. Deconfinement transition as a black hole formation by the condensation of QCD string

Masanori Hanada (Stanford/Kyoto)

23/06/2014, 16:30

Nonzero Temperature and Density

Talk

In the gauge/gravity duality, the deconfinement transition in the gauge theory is identified with a formation of black hole in the dual gravity theory. In this talk, firstly we give quantitative evidence for this identification from the thermodynamic study of the supersymmetric theory. Then we consider generic gauge theories, including QCD, and show that the deconfinement transition is the...

240. Fluctuations of the electric charge in theory and experiment

Dr Szabolcs Borsanyi (Bergische Universität Wuppertal)

23/06/2014, 16:30

Nonzero Temperature and Density

Talk

We present the continuum extrapolated kurtosis, skewness and variance of the electric charge in a grand canonical ensemble with zero or small chemical potential. This observable his a particular relevance in Heavy Ion Physics since ratios of such fluctuations have been measured in experiment at the chemical freeze-out. We discuss how lattice results describe the STAR fluctuation data at...

377. Gluonic Correlations at Deconfinement

Tereza Mendes (University of Sao Paulo)

23/06/2014, 16:50

Vacuum Structure and Confinement

Talk

We investigate the critical behavior of electric and magnetic gluon propagators around the deconfinement temperature of SU(2) gauge theory on large lattices, employing Landau gauge. In particular, we study the analytic properties of these propagators using several trial fitting functions.

382. Thermodynamics of heavy-light hadrons

Prof. Heng-Tong DING (Central China Normal University)

23/06/2014, 16:50

Nonzero Temperature and Density

Talk

Ratios of cumulants of conserved net charge fluctuations are sensitive to the degrees of freedom that are carriers of the corresponding quantum numbers in different phases of strong interaction matter. We calculate second and fourth order cumulants of net charm and strange fluctuations and their correlations with other conserved charges such as net baryon number and electric...

357. Exploring the QCD phase diagram with conserved charge fluctutaions

Dr Christian Schmidt (Universitaet Bielefeld)

23/06/2014, 17:10

Nonzero Temperature and Density

Talk

Higher order cumulants of fluctuations of conserved charges are an important diagnostic tool for the thermodynamic properties of strong interacting matter close to freeze out at LHC energies as well as in the entire energy range covered with the beam energy scan (BES) at RHIC. We present recent progress on the calculation of conserved charge fluctuations with highly improved staggered quarks...

9. Locating the critical end-point of QCD

Prof. Christian Fischer (JLU Giessen)

23/06/2014, 17:10

Nonzero Temperature and Density

Talk

I will give an overview on our recent results for the phase diagram of QCD with Nf=2+1 and Nf=2+1+1 flavors. We use a combination of lattice and Dyson-Schwinger methods to determine the chiral and deconfinement order parameters at finite temperature and chemical potential. We find a critical end-point at large chemical potential in the vicinity of the chiral critical line extrapolated...

421. Fluctuation effects on QCD phase diagram at strong coupling

Mr Terukazu Ichihara (Yukawa Institute for Theoretical Physics and Kyoto University)

23/06/2014, 17:30

Nonzero Temperature and Density

Talk

We investigate QCD phase diagram at strong coupling based on strong coupling expansion in auxiliary field Monte-Carlo (AFMC) method. The strong coupling expansion is one of the ways to reduce the sign problem since the effective action is described in hadronic degrees of freedom via analytic integration over link variables. We have found that hadron phase is compressed (extended) at low...

60. Quark number density at imaginary chemical potential and its extrapolation to large real chemical potential by the effective model

Mr Junichi Takahashi (Kyushu University)

23/06/2014, 17:30

Nonzero Temperature and Density

Talk

We evaluate quark number densities at imaginary chemical potential by doing lattice QCD calculations on an 8^2*16*4 lattice with clover-improved Wilson quarks of two flavors. The quark number densities are extrapolated to the small real chemical potential region by assuming some function forms. The extrapolated quark number densities are consistent with those calculated at real chemical...

287. On curing the divergences in the quark number susceptibility

Prof. Rajiv Gavai (Tata Institute of Fundamental Research)

23/06/2014, 17:50

Nonzero Temperature and Density

Talk

Quark number susceptibility on the lattice, obtained by merely adding a \mu N-term with \mu as the chemical potential and N as the conserved quark number, has a quadratic divergence in the cut-off a. We show that it is simply a faithful representation of the corresponding continuum result. While one can eliminate it in the free theory by suitably modifying the action, as is popularly done,...

352. Temperature dependence of meson screening masses; a comparison of effective model with lattice QCD

Mr Masahiro Ishii (Kyushu University)

23/06/2014, 17:50

Nonzero Temperature and Density

Talk

We analyze the pion screening mass calculated with lattice QCD, using the entanglement-PNJL (EPNJL) model. The EPNJL model well reproduces the lattice QCD result. We then predict the sigma meson screening mass with the model. The chiral symmetry restoration can be exhibited by the difference between the pi and sigma meson screening masses. After the chiral symmetry restoration, the two...

217. Renormalization group flow of linear sigma model with UA(1) anomaly

Mr Tomomi Sato (The Graduate University for Advanced Studies)

23/06/2014, 18:10

Nonzero Temperature and Density

Talk

Motivated by recent arguments on effective restoration of UA(1) symmetry around the critical temperature in two-flavor QCD, we investigate the renormalization group flow of the U(2)xU(2) linear sigma model (LSM) with the traditional epsilon expansion. Introducing the UA(1) violation, the attractive basin falling into the O(4) LSM in the parameter space and its dependence on the size of UA(1)...

389. The Combinatorics of Lattice QCD at Strong Coupling

Dr Wolfgang Unger (University Frankfurt)

23/06/2014, 18:10

Nonzero Temperature and Density

Talk

We compare the combinatorics of staggered and Wilson fermions in the strong coupling limit for various colors and flavors. Based on the hopping parameter expansion, we express the partition functions of both discretizations in terms of polynomials with coefficients of distinct combinatorical interpretation. We address how gauge corrections to the strong coupling limit modify the...

170. The N_f=3 critical endpoint with smeared staggered quarks

Mr Lukas Varnhorst (Bergische Universität Wuppertal)

24/06/2014, 14:15

Nonzero Temperature and Density

Talk

We present preliminary results for the determination of the critical endpoint of the chiral transition in N_f=3 QCD with mu=0 at small N_t. We have employed an unimproved Wilson gauge action with staggered fermions, for which previous results on the critical endpoint are available. As an extension of these results we have studied the dependence of the critical mass on the strength of the smearing.

202. Update on the critical endpoint of the finite temperature phase transition for three flavor QCD with clover type fermions

Dr Yoshifumi Nakamura (RIKEN Advanced Institute for Computational Science)

24/06/2014, 14:35

Nonzero Temperature and Density

Talk

We present preliminary results on the critical endpoint of three flavor QCD at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and $O(a)$-improved Wilson fermion action. The critical endpoint is determined by using the intersection points of kurtosis for mixed observable as well as plaquette, gange action density, Polyakov loop and "chiral...

231. Scalar correlators near the 3-flavor thermal critical point

Xiao-Yong Jin (RIKEN Advanced Institute for Computational Science)

24/06/2014, 14:55

Nonzero Temperature and Density

Talk

We investigate screening masses at finite temperatures with 3 flavors using the non-perturbatively improved clover fermion action and the Iwasaki gauge action. This report focuses on the behavior of the scalar singlet correlator near the thermal critical point. I will explain the technique used to extract the correlator and discuss our preliminary results from ensembles at Nt=8.

200. Critical end point in Nf=3 QCD with finite density and temperature

Dr Shinji TAKEDA (Kanazawa University)

24/06/2014, 15:15

Nonzero Temperature and Density

Talk

We investigate a presence of critical end point in finite density/temperature QCD with three-degenerated Wilson-Clover quarks. The critical end point is estimated by the kurtosis intersection method and a gap of transition points between two independent observables. We also discuss slope/curvature of the critical end line extending from the zero density point whose details will be given in a...

395. Search for the chiral phase transition in three flavor QCD at imaginary chemical potential

Dr Balint Toth (University of Wuppertal)

24/06/2014, 15:35

Nonzero Temperature and Density

Talk

The finite temperature transition of QCD with three degenerate flavors is expected to become a first order phase transition at small quark masses. It has been observed that introducing a sufficiently large imaginary chemical potential broadens the first order region and raises the critical quark mass to the numerically feasible regime. We report on our search for this first order transition at...

214. Canonical approach to the finite density QCD with winding number expansion

Dr Yusuke Taniguchi (University of Tsukuba)

24/06/2014, 16:30

Nonzero Temperature and Density

Talk

The canonical partition function is related to the grand canonical one through the fugacity expansion. In this talk we perform the fugacity expansion by a method of the hopping parameter expansion in temporal direction: winding number expansion. Since the convergence of our expansion is good only for a small $\kappa$ we concentrate on heavy quark mass region. For a numerical simulation...

252. Complex Langevin dynamics for SU(3) gauge theory in the presence of a theta term

Mr Lorenzo Bongiovanni (Swansea University)

24/06/2014, 16:50

Nonzero Temperature and Density

Talk

Recently progress has been made in applying complex Langevin dynamics to nonabelian gauge theories with a sign problem. Here we study the SU(3) gauge theory with a theta therm and present results at real theta.

259. Exploring the phase diagram of QCD with complex Langevin simulations

Mr Benjamin Jaeger (Swansea University)

24/06/2014, 17:10

Nonzero Temperature and Density

Talk

Simulations with a finite chemical potential typically lead to a severe sign problem, prohibiting any standard Monte Carlo approach. For simulations of QCD we use the complex Langevin method, for which we apply adaptive step-sizes and gauge cooling to ensure the convergence. We present preliminary results for heavy quark QCD and explore the application for two dynamical quarks.

294. Towards exact worldline models of lattice gauge theory at finite density

Helvio Vairinhos (University of Porto)

24/06/2014, 17:30

Nonzero Temperature and Density

Talk

We integrate out all the link variables in the partition function of SU(N) or U(N) lattice gauge theory with the Wilson plaquette action, for arbitrary values of the lattice coupling. The partition function is recast as a Gaussian integral over auxiliary fields, after using suitable Hubbard-Stratonovich transformations. We extend our formalism to lattice gauge theories with staggered fermions...

423. Solution of simple toy models via thimble regularization of lattice field theory

Dr Eruzzi Giovanni (University of Parma and INFN)

24/06/2014, 17:50

Nonzero Temperature and Density

Talk

The sign problem prevents lattice simulations of many models of physical interest. One proposal for evading such problems is the thimble regularization. I will discuss its application to the phi^4 0-dimensional integral, which is a toy model that has been studied for many years as a prototype of complex-valued action and raises several problems within a treatment via complex Langevin; this...

220. Axial U(1) symmetry at finite temperature with Mobius domain-wall fermions

Dr Guido Cossu (KEK)

25/06/2014, 09:00

Nonzero Temperature and Density

Talk

Possible (effective) restoration of the axial U(1) symmetry at finite temperature has attracted a lot of attention in the last few years thanks to the development of the chiral lattice actions and algorithmic improvements. In our previous work we utilized the overlap fermion formulation to show an evidence for a restoration of the axial symmetry above the phase transition. In this work we...

332. Effects of near-zero Dirac eigenmodes on axial U(1) symmetry at finite temperature

Mr Akio Tomiya (Osaka University)

25/06/2014, 09:20

Nonzero Temperature and Density

Talk

We investigate the issue of possible restoration of the axial U(1) symmetry at finite temperature, using lattice simulations with the Mobius domain-wall fermion. In this talk, we focus on the effects of near-zero Dirac eigenmodes, which play a crucial role for both SU(2)xSU(2) chiral symmetry restoration and the restoration/breaking of axial U(1) symmetry. Performing simulations at two...

399. Dirac eigenmodes at the QCD Anderson transition

Prof. Tamas G. Kovacs (Institute for Nuclear Research, Debrecen)

25/06/2014, 09:40

Nonzero Temperature and Density

Talk

Recently we found an Anderson-type localization-delocalization transition in the QCD Dirac spectrum at high temperature. Using spectral statistics we obtained a critical exponent compatible with that of the corresponding Anderson model. Here we study the spatial structure of the eigenmodes both in the localized and the transition region. Based on previous studies in the Anderson model, at the...

262. Understanding localisation in QCD through an Ising-Anderson model

Dr Matteo Giordano (Institute for Nuclear Research (ATOMKI), Debrecen)

25/06/2014, 10:00

Nonzero Temperature and Density

Talk

Above the QCD chiral crossover temperature, the low-lying eigenmodes of the Dirac operator are localised, while moving up in the spectrum states become extended. This localisation/delocalisation transition has been shown to be a genuine second-order phase transition, in the same universality class as that of the 3D Anderson model. The existence of localised modes and the effective dimensional...

369. Chiral transition as Anderson transition

Dr Ferenc Pittler (Eotvos Lorand University)

25/06/2014, 10:20

Nonzero Temperature and Density

Talk

At low temperature the low-lying QCD Dirac spectrum obeys random matrix statistics. Recently we found that above $T_c$ the lowest part of the spectrum consists of localized modes that obey Poisson statistics. An interesting implication of this is that as the system crosses $T_c$ from above, the spectral statistics at $\lambda =0$ changes from Poisson to random matrix. Here we study this...

232. Charmonium spectra and dispersion relation with improved Bayesian analysis in lattice QCD

Mr Atsuro Ikeda (Osaka University)

25/06/2014, 11:10

Nonzero Temperature and Density

Talk

We study the charmonium property at finite temperature and finite momentum in quenched lattice QCD with improved maximum entropy method (MEM). We extend the MEM analysis to the product space of the correlation functions at more than two different momenta to take advantage of more data and the strong correlation among Euclidean correlators with different momenta. We find that this method...

242. Mesonic spectral functions and transport properties in the quenched QCD continuum

Mr Florian Meyer (University of Bielefeld, Germany)

25/06/2014, 11:30

Nonzero Temperature and Density

Talk

We present new results on the reconstruction of mesonic spectral functions for three temperatures above T_c in quenched QCD. Making use of Clover improved Wilson valence quarks allows for a clean extrapolation of correlator data to the continuum. For the case of vanishing momentum the spectral function is obtained by fitting the data to a well motivated ansatz. In the vector channel for...

309. Temperature dependence of bottomonium spectral functions

Mr Tim Harris (Trinity College, University of Dublin)

25/06/2014, 11:50

Nonzero Temperature and Density

Talk

I will present updated results from the FASTSUM collaboration on the bottomonium spectrum at finite temperature from lattice NRQCD on anisotropic $N_f=2+1$ Wilson clover ensembles. Further systematic checks on the reconstruction of the spectral function at high temperatures where few correlator data are available will be discussed. This is relevant to understand the reliability of the...

320. Charmonium spectral functions from 2+1 flavour lattice QCD

Mr Attila Pasztor (MTA-ELTE Lendulet Lattice gauge theory research group/Eotvos University)

25/06/2014, 12:10

Nonzero Temperature and Density

Talk

Finite temperature charmonium spectral functions in the pseudoscalar and vector channels are studied in lattice QCD with 2+1 flavours of dynamical Wilson quarks, on fine isotropic lattices (with a lattice spacing of 0.057fm), with a pion mass of 545MeV. The highest temperature studied is approximately 1.4Tc. Up to this temperature no significant variation of the spectral function is seen in...

325. Quark mass dependence of quarkonium properties at finite temperature

Dr Hiroshi Ohno (Center for Computational Sciences, University of Tsukuba)

25/06/2014, 12:30

Nonzero Temperature and Density

Talk

Quarkonium properties at finite temperature are studied with various quark masses in the range between those for the charm and bottom quarks. Our simulations are performed in quenched QCD with the $O(a)$-improved Wilson quarks on large and fine isotropic lattices at temperatures between about 0.7$T_c$ and 1.4$T_c$. At both vanishing and finite momenta we discuss temperature and quark mass...

335. The in-medium heavy quark potential from quenched and dynamical lattice QCD

Dr Alexander Rothkopf (Institute for Theoretical Physics, Heidelberg University)

25/06/2014, 12:50

Nonzero Temperature and Density

Talk

We present the latest results from two projects focused on determining the temperature dependence of the heavy quark potential from lattice QCD. The real and imaginary part of this real-time potential is obtained from the position and width of the lowest lying peak in the Coulomb gauge Wilson line correlator spectral function [1]. Spectral information is extracted from Euclidean time data...

65. Thermodynamics in the fixed scale approach with the shifted boundary conditions

Takashi Umeda (Hiroshima University)

26/06/2014, 14:15

Nonzero Temperature and Density

Talk

The fixed scale approach has various advantages to calculate the QCD equation of state on lattices. In this approach a series of temperatures are realized with single coupling parameters. Therefore zero temperature subtractions are common, and conditions for the line of constant physics are automatically satisfied. We test the fixed scale approach to study thermodynamics of SU(3) gauge theory...

205. Multipoint reweighting method and beta-functions for the calculation of QCD equation of state

Mr Ryo IWAMI (Niigata University)

26/06/2014, 14:35

Nonzero Temperature and Density

Talk

We discuss the reweighting method aiming numerical studies of QCD at finite density, in which the Monte-Carlo method cannot be applied directly. One of the most important problems in the reweighting method is the overlap problem. To solve the problem, we propose the following reweighting method: simulations are performed at several simulation points and the analysis is done combining all data....

321. QCD Thermodynamics With Continuum Extrapolated Wilson Fermions

Mr Norbert Trombitas (Eotvos Lorand University)

26/06/2014, 14:55

Nonzero Temperature and Density

Talk

We study 2+1 flavour QCD thermodynamics using Wilson fermions in the fixed scale approach. The temperature dependence of the renormalized chiral condensate, quark number susceptibility and Polyakov loop is determined at three pion masses down to 280~MeV. Four lattice spacings are used allowing for a controlled continuum limit.

162. Recent results on the Equation of State of QCD

Dr Stefan Krieg (Forschungszentrum Juelich GmbH/Wuppertal University)

26/06/2014, 15:15

Nonzero Temperature and Density

Talk

I will review results for the Equation of State of QCD, in particular I will give an update on our calculation that includes a dynamical charm quark.

398. The QCD Equation of State

Tanmoy Bhattacharya (LANL)

26/06/2014, 15:35

Nonzero Temperature and Density

Talk

The HotQCD Collaboration has calculated the equation of state in 2+1 flavor QCD at zero net baryon density using the Highly Improved Staggered Quark (HISQ) action. The strange quark mass was set to its physical value and the light (up/down) quark masses used correspond to a pion mass of 160 MeV in the continuum limit. Lattices with temporal extent Nt=6, 8, 10 and 12 were used, and the...

393. The QCD Equation of State at order ${\mu }_B^4$

Dr Prasad Hegde (Central China Normal University)

26/06/2014, 15:55

Nonzero Temperature and Density

Talk

Hydrodynamic models of heavy-ion collisions have increasingly begun to rely on lattice results for the Equation of State. While the lattice has the advantage of being a first-principles approach to QCD, the notorious sign problem prevents a direct determination of the equation of state and other thermodynamic observables at finite chemical potential ${\mu }_B$. Quark number susceptibilities...

428. The QCD Phase Transition with Three Physical-Mass Pions

Dr Chris Schroeder (LLNL)

26/06/2014, 16:15

Nonzero Temperature and Density

Talk

On behalf of the HotQCD collaboration, I present results from the first lattice study of the QCD phase transition using chiral fermions and physical quark masses. With domain wall fermions, the dislocation suppressing determinant ratio (DSDR), a temporal Euclidean extent of 8 sites, and spatial extents of at least 4 and up to 11 fm, we have computed the disconnected chiral susceptibility for...

164. Deconfining temperatures in SO(N) and SU(N) gauge theories

Richard Lau (University of Oxford)

27/06/2014, 14:15

Nonzero Temperature and Density

Talk

We present our current results for the deconfining temperatures in SO(N) gauge theories in 2+1 dimensions. SO(2N) theories may help us to understand QCD at finite chemical potential since there is a large-N orbifold equivalence between SO(2N) QCD-like theories and SU(N) QCD and SO(2N) theories do not have the sign problem present in QCD. We show that the deconfining temperatures in these two...

238. The density of states from first principles

Dr Roberto Pellegrini (College of Science, Swansea University, Swansea, SA2 8PP, UK)

27/06/2014, 14:35

Nonzero Temperature and Density

Talk

We present a novel algorithm to compute the density of states, which is proven to converge to the correct result. The algorithm is very general and can be applied to a wide range of models, in the frameworks of statistical mechanics and lattice gauge theory. All the thermal or quantum expectation values can then be obtained by a simple integration of the density of states. As an...

192. A novel density of state method for complex action system

Prof. Lucini Biagio (Swansea University)

27/06/2014, 14:55

Nonzero Temperature and Density

Talk

Recently, a new and efficient algorithm (the LLR method) has been proposed for computing density of states in statistical systems and gauge theories. In this talk, we explore whether this novel density of state method can be applied to numerical computations of observables in systems for which the action is complex. To this purpose, we introduce a generalised density of states, in terms of...

189. Quark number susceptibilities from fugacity expansion at finite chemical potential

Hans-Peter Schadler (University of Graz)

27/06/2014, 15:15

Nonzero Temperature and Density

Talk

Generalized quark number susceptibilities have been proposed to be good probes for the phase transition in QCD and in the search of a critical point. In this work we explore the possibilities of the expansion in the fugacity parameter $e^{\mu \beta }$ which has features which make, in particular, quark number related bulk observables easily accessible. We will present results at finite chemical...

379. Shear Viscosity from Lattice QCD

Mr Simon Mages (University of Regensburg)

27/06/2014, 15:35

Nonzero Temperature and Density

Talk

This talk is on recent efforts to determine the shear viscosity $\eta$ in the deconfined phase from lattice QCD. The main focus is on the integration of the Wilson flow in the analysis to get a better handle on the infrared behaviour of the spectral function which is relevant for transport. Also the non-perturbative renormalization strategy applied for the energy momentum tensor is discussed....

64. Effective Polyakov line actions, and their solutions at finite chemical potential

Dr Jeff Greensite (San Francisco State University)

27/06/2014, 16:30

Nonzero Temperature and Density

Talk

I explain the “relative weights” strategy for deriving effective Polyakov line actions, at finite chemical potentials, from the underlying lattice gauge theories. Gauge-Higgs and heavy quark models are the examples considered. The effective Polyakov line theories still have a severe sign problem, and I compare results obtained using mean field and complex Langevin methods to solve such theories.

312. Chiral dynamics in the low-temperature phase of QCD

Mr DANIEL ROBAINA (Institute of Nuclear Physics. Johannes Gutenberg University Mainz)

27/06/2014, 16:50

Nonzero Temperature and Density

Talk

We investigate the low-temperature phase of QCD and the crossover region with two light flavors of quarks. The chiral expansion around the point $(T,m_q=0)$ in the temperature vs. quark-mass plane indicates that a sharp real-time excitation exists with the quantum numbers of the pion. We determine its dispersion relation and test the applicability of the chiral expansion. The time-dependent...

160. Two-color QCD with chiral chemical potential

Mr Andrey Kotov (ITEP, Moscow)

27/06/2014, 17:10

Nonzero Temperature and Density

Talk

We present preliminary results of the study lattice SU(2) QCD phase diagram with chiral chemical potential. The simulation is carried out with dynamical staggered fermions without rooting. The dependences of the chiral density, Polyakov loop, chiral condensate and corresponding susceptibilities on the chiral chemical potential and temperature are measured.

55. Deconfinement transition in two-flavour lattice QCD with dynamical overlap fermions in an external magnetic field

Mr Oleg Kochetkov (University of Regensburg)

27/06/2014, 17:30

Nonzero Temperature and Density

Talk

We study the influence of an external magnetic field on the deconfinement transition in two-flavour lattice QCD with physical quark charges. We use dynamical overlap fermions without any approximation such as fixed topology and perform simulations on a 16^3×6 lattice and at a pion mass around 500 MeV. The pion mass (as well as the lattice spacing) was determined in the independent runs on...

297. Magnetic properties of the QCD medium

Mr Marco Mariti (University of Pisa & INFN)

27/06/2014, 17:50

Nonzero Temperature and Density

Talk

We present improved results regarding our determination of the magnetic susceptibility in QCD. We discuss also preliminary data on higher order terms contributions in B to the free energy and to the relative increase in the pressure.

401. Effects of an external magnetic field on the QGP

Ludmila Levkova (University of Utah)

27/06/2014, 18:10

Nonzero Temperature and Density

Talk

We present results for the pressure of the quark-gluon plasma in the presence of a strong magnetic filed, calculated using a Taylor expansion in the field to 4th order. Our method does not require quantization of the magnetic filed and is computationally cheaper than calculations on ensembles generated with explicit magnetic fields.