# The 35th International Symposium on Lattice Field Theory

18-24 June 2017
Palacio de Congresos
Home > Timetable > Session details
PDF | iCal

# Nonzero Temperature and Density

## Place

Location: Palacio de Congresos
Date: from 19 Jun 14:30 to 23 Jun 19:10

## Conveners

• 19 Jun 14:30 - 16:10
• Prof. Kitazawa, Masakiyo (Osaka University)
• 19 Jun 16:40 - 18:00
• Dr. Bazavov, Alexei (Michigan State University)
• 20 Jun 15:00 - 16:40
• Prof. Kawamoto, Noboru (Hokkaido University)
• 20 Jun 15:00 - 16:40
• Prof. Ohnishi, Akira (Yukawa Institute for Theoretical Physics, Kyoto University)
• 20 Jun 17:10 - 19:10
• Yamamoto, Arata (University of Tokyo)
• 21 Jun 09:00 - 11:00
• Dr. Sinclair, Donald (Argonne National Laboratory)
• 21 Jun 11:30 - 13:30
• Heller, Urs
• 21 Jun 11:30 - 13:30
• Prof. Hands, Simon (Swansea University)
• 22 Jun 15:00 - 16:40
• Dr. Creutz, Michael (Brookhaven Lab)
• 22 Jun 17:10 - 19:10
• Prof. Caselle, Michele (Dipartimento di Fisica, Universita' di Torino and INFN, Sez. di Torino)
• 23 Jun 15:00 - 16:40
• Prof. Gavai, Rajiv V (Tata Institute (TIFR), Mumbai)
• 23 Jun 17:10 - 19:10
• Mr. de FORCRAND, Philippe (ETH Zurich)

## Timetable | Contribution List

Displaying 63 contributions out of 63
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We present a study of the finite density lattice Thirring model in 2 dimensions using the world-line/fermion-bag algorithm. The model has features similar to QCD and provides a test case to explore the accuracy of various methods to solve sign problems. In the massless limit and with open boundary conditions we show that the sign problem is an artifact of the auxiliary field approach and is comple ... More
Presented by Dr. Jarno RANTAHARJU on 22/6/2017 at 17:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We estimate the production rate of photons from the quark-gluon plasma in lattice QCD. The production of weakly-interacting particles from a strongly-interacting medium has applications to particle cosmology and heavy-ion phenomenology. We propose a new observable which gives us better control over the systematic uncertainty in estimating the rate at large photon momenta. The relevant Euclidean ... More
Presented by Dr. Tim HARRIS on 23/6/2017 at 15:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In order to estimate the photon rate from the Euclidean vector current correlation functions, an inverse problem for the vector-channel spectral function must be solved. We use both a direct model for the spectral function and a model-independent estimate from the Backus-Gilbert method to give a robust estimate for the photon rate at momenta close to its maximum. At low photon momenta, the exis ... More
Presented by Mr. Aman STEINBERG on 23/6/2017 at 16:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In QCD above the deconfinement temperature there exists an Anderson transition in the fermion spectrum from localized to delocalized modes. We investigate whether the same holds for nonlinear sigma models. In particular we study the spectra of fermions coupled to (quenched) CP(N-1) configurations at high temperatures. We compare results in two and three space-time dimensions: in two dimensio ... More
Presented by Mr. jacob WELLNHOFER on 19/6/2017 at 15:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study the low temperature region of the $T-\mu_B$ phase diagram of QCD with $N_f$=2 and 4 flavors of staggered fermions with the density of states method. We generate configurations at finite isospin chemical potential using different observables as constrained quantities: the gauge action and the pion condensate.
Presented by Mr. Csaba TOROK on 20/6/2017 at 16:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We investigate the axial $U(1)$ symmetry breaking above the critical temperature in 2-flavor lattice QCD whose ensembles are generated with Mobius domain-wall fermions. We will discuss the temperature and quark mass dependence of $U(1)_A$ susceptibility extracted from the spectra of overlap Dirac eigenmodes. The behavior of $U(1)_A$ susceptibility is compared with that of topological susceptib ... More
Presented by Dr. Kei SUZUKI on 19/6/2017 at 14:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In the worldline formulation the particle number of a lattice quantum field theory assumes an elegant topological form: it is the winding number of the worldlines around the compactified time direction. In a numerical worldline simulation one can implement the canonical ensemble by using only updates that preserve the winding number and thus the number of particles. We explore the idea of a canoni ... More
Presented by Mr. Oliver ORASCH on 22/6/2017 at 14:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Lattice simulations for (2+1)-flavor QCD demonstrated that the quark mass is one of the important parameters responsible for the (inverse)-magnetic catalysis. In this talk we will discuss the dependence of chiral condensates and susceptibilities on the magnetic field in three flavor QCD in the regime of the first order phase transition. The lattice simulations were performed using standard stagger ... More
Presented by Dr. Akio TOMIYA on 19/6/2017 at 15:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study correlation functions of a static quark antiquark pair in spatial separation in 2+1 flavor QCD in order to better understand the nature of color screening at high temperatures. We performed lattice calculations in a wide temperature range $140$ MeV $\leq T \leq 5.8$ GeV using the using the highly improved staggered quark (HISQ) action and several lattice spacings to control discretizatio ... More
Presented by Dr. Johannes WEBER on 20/6/2017 at 16:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In application of the complex Langevin method to finite density QCD at low temperature, the singular-drift problem occurs due to the appearance of near-zero eigenvalues of the Dirac operator. In order to avoid this problem, we proposed to deform the Dirac operator in such a way that the near-zero eigenvalues do not appear and to extrapolate the deformation parameter to zero from the available data ... More
Presented by Dr. Yuta ITO on 20/6/2017 at 17:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We have extended our CLE simulations of lattice QCD at a finite quark-number chemical potential, $\mu$, on a $12^4$ lattice at $\beta=6/g^2=5.6$ to a weaker coupling, $\beta=5.7$, and larger, $16^4$, lattice. Limitations of the method and choice of lattice fermions are discussed as are possible improvements.
Presented by Dr. Donald SINCLAIR on 20/6/2017 at 18:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study QCD at finite density and low temperature by using the complex Langevin method. We employ the gauge cooling to control the unitarity norm and introduce a deformation parameter in the Dirac operator to avoid the singular drift problem. The reliability of the obtained results are judged by the probability distribution of the magnitude of the drift term. By extrapolating the reliable results ... More
Presented by Dr. Shinji SHIMASAKI on 20/6/2017 at 17:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We use a dual worldline representation to study the relativistic Bose gas at finite density. At low temperature we identify the thresholds for one- and two-particle condensation. We study these thresholds as a function of the spatial size and use the Lüscher formula to determine the scattering length.
Presented by Mr. Mario GIULIANI on 22/6/2017 at 16:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
For the investigation of in-medium modifications of quarkonia and for determining heavy quark diffusion transport coefficients, correlation functions of heavy mesons play a crucial role. For the first time we performed a continuum extrapolation of charmonium correlators in the vector and pseudoscalar channels based on non-perturbatively clover improved Wilson fermions in quenched lattice QCD. We p ... More
Presented by Mr. Hauke SANDMEYER on 19/6/2017 at 17:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We carry out the continuum extrapolation of the critical point for finite temperature QCD with Nf=3 using several temporal lattice sizes N_t=4, 6, 8 and 10. We employ the Iwasaki gauge action and non-perturbatively O(a) improved Wilson fermions. We estimate the critical pseudo-scalar meson mass and temperature.
Presented by Dr. SHINJI TAKEDA on 20/6/2017 at 15:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We investigate the critical endline of the finite temperature phase transition of QCD away from the SU(3)-flavor symmetric point at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and non-perturbatively $O(a)$-improved Wilson-clover fermion action. The critical endline is determined by using the intersection point of kurtosis, employing the multi-parame ... More
Presented by Dr. Yoshifumi NAKAMURA on 20/6/2017 at 15:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We studied the critical endpoint of 4-flavor QCD at finite temperature and zero chemical potential. Our lattice QCD simulations have been performed with the Iwasaki gauge and the non-perturbatively $O(a)$-improved Wilson fermion actions on lattices with $N_t$ = 4, 6 and 8. We determined the critical endpoint from an intersection point of kurtosis of the chiral condensate with three different volum ... More
Presented by Dr. Hiroshi OHNO on 21/6/2017 at 11:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study spatial isovector meson correlators in Nf=2 QCD with dynamical domain-wall fermions on the 32^3x8 lattices at temperatures T=170-380MeV with various quark masses. We measure the correlators of spin-one operators including vector ("V", 1--), axial-vector ("AV",1++), tensor ("T", 1--) and axial-tensor ("AT", 1+-). At temperatures above T_c, we observe a degeneracy of the correlators in th ... More
Presented by Mr. Christian ROHRHOFER on 21/6/2017 at 10:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study spectral properties of charmonia in the vector and pseudoscalar channels at nonzero momenta on quenched lattices focusing on the dispersion relation and the weight of the peak. The spectral functions of charmonia are studied by the maximum entropy method with the lattice Euclidean correlation functions on the anisotropic quenched lattices. The errors of the dispersion relations and th ... More
Presented by Prof. Masakiyo KITAZAWA on 19/6/2017 at 16:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We present the computation of invariants that arise in the strong coupling expansion of lattice QCD. These invariants allow to perform Monte Carlo simulations of Young Mills Theory and Lattice QCD with staggered fermions in a dual, color singlet representation. This formulation is in particular useful to tame the finite density sign problem.
Presented by Dr. Wolfgang UNGER on 21/6/2017 at 12:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The dual form of the massless Schwinger model on the lattice overcomes the complex action problems from two sources: from a topological term, as well as from non-zero chemical potential, making these physically interesting cases accessible to Monte Carlo simulations. The partition function is represented as a sum over fermion loops, dimers and plaquette-surfaces such that all contributions are ... More
Presented by Mr. Daniel GOESCHL on 22/6/2017 at 17:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We measure correlation functions of energy-momentum tensor in Nf=2+1 full QCD at finite temperature by applying the gradient flow method both to the gauge and quark fields. Our main interest is to study the conservation law of the energy-momentum tensor and to extract thermodynamical quantities from the correlation function. We adopt a fine lattice spacing a=0.07 (fm) and cover a wide range of ... More
Presented by Dr. Yusuke TANIGUCHI on 20/6/2017 at 15:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We report the equation of state at finite chemical potential, namely the baryon number density and the baryonic contribution to the pressure, using a resummation of the Taylor expansion. We also report the freezeout conditions for a measure of fluctuations. We examine the major sources of systematic and statistical errors in all of these measurements.
Presented by Prof. Sourendu GUPTA on 23/6/2017 at 18:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study the energy-momentum tensor and the equation of state as well as the chiral condensate in (2+1)-flavor QCD at the physical point applying the method of Makino and Suzuki based on the gradient flow. Following a strategy of our previous study at a heavier quark mass, we adopt a nonperturbatively O(*a*)-improved Wilson quark action and the renormalization group-improved Iwasaki gauge action a ... More
Presented by Prof. Kazuyuki KANAYA on 21/6/2017 at 11:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We report on the lattice computation of the Landau gauge gluon propagator at finite temperature, including the non-zero Matsubara frequencies. Furthermore, the Källén-Lehmann representation is inverted and the corresponding spectral density evaluated using a Tikhonov regularisation together with the Morozov discrepancy principle. Implications for gluon confinement are also discussed.
Presented by Dr. Paulo SILVA on 22/6/2017 at 15:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
When comparing lattice calculation to experimental data from heavy ion collision experiments, the higher order fluctuations of conserved charges are important observables. An efficient way to study these fluctuations is to determine them from simulations at imaginary chemical potential. In this talk we present results up to the eighth order derivative in muB, calculated on a 48^3x12 lattice with s ... More
Presented by Jana GUENTHER on 23/6/2017 at 15:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
SU(2) is the simplest non-abelian gauge theory with fermions without sign problem. Therefore its study on the lattice is a benchmark for other non-perturbative approaches at finite density. We study the Landau-gauge 2-point and 3-point correlation functions of the gauge sector and the running gauge coupling at finite density, and compare them to the vacuum case. We observed no significant ef ... More
Presented by Ms. Ouraman HAJIZADEH on 21/6/2017 at 11:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We use 4stout improved staggered lattice data at imaginary chemical potentials to calculate virial coefficients in finite temperature QCD. Since the virial expansion is an expansion in the fugacity, i.e. the exponential of the chemical potential, for imaginary chemical potentials the coefficients simply become Fourier coefficients, allowing for an accurate determination from our simulations. We ... More
Presented by Attila PASZTOR on 23/6/2017 at 18:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The sign problem in particle physics appears in QCD as soon as a non-zero chemical potential is introduced. This prevents direct lattice simulations to determine the phase structure of the strongly interacting matter. Complex Langevin methods have been successfully used for various models or approximations of QCD, however, in some scenarios it converges to incorrect results. We will present a new ... More
Presented by Dr. Benjamin JAEGER on 20/6/2017 at 18:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse probl ... More
Presented by Dr. Alexander ROTHKOPF on 19/6/2017 at 15:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
I will discuss the issue of Landau levels of quarks in lattice QCD in an external magnetic field. I will show that in the two-dimensional case the lowest Landau level can be identified unambiguously even if the strong interactions are turned on. Starting from this observation, I will then show how one can define a "lowest Landau level" in the four-dimensional case, and discuss how much of the obse ... More
Presented by Dr. Matteo GIORDANO on 19/6/2017 at 15:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The canonical approach is a powerful tool to circumvent sign problem in LQCD. Although it has its own difficulties it provides opportunity to determine QCD phase transition line. Using improved Wilson fermions we calculated number density at nonzero imaginary chemical potential for confinement and deconfinement phases, restored canonical partition functions Zn and did extrapolation into the real ... More
Presented by Mr. Denis BOYDA on 23/6/2017 at 17:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Lefschetz-thimble method becomes a powerful tool to study the sign problem. It defines the steepest descent contours by the gradient flow in complexified field configurations. Solutions of the gradient flow, however, generically blow up in a finite time, and thus it must be solved with great cares. We propose a new gradient flow without blow-ups that equally solves the sign problem as the conv ... More
Presented by Dr. Yuya TANIZAKI on 21/6/2017 at 7:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study the phase diagram of QCD at finite isospin density using two flavors of staggered quarks. We investigate the low temperature region of the phase diagram where we find a pion condensation phase at high chemical potential. We started a basic analysis of the spectrum at finite isospin density. In particular, we measured pion masses inside and outside of the pion condensation phase. In agre ... More
Presented by Dr. Philipp SCIOR on 20/6/2017 at 16:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We analyse the behaviour of hyperons with strangeness $S=-1,-2$ in the hadronic and quark gluon plasma phases, with particular interest in parity doubling and its emergence as the temperature grows. This study uses our FASTSUM anisotropic $N_f = 2 + 1$ ensembles, with four temperatures below and four above the deconfinement transition temperature, $T_c$. The positive-parity groundstate masses ... More
Presented by Davide DE BONI on 20/6/2017 at 16:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We compare the low eigenvalue spectra of the Overlap Dirac operator on sets of dynamical configurations at $\mu_I/mu_I^c$ = 0.5, 1.5, 3 and 4. These were generated with dynamical staggered fermions on $24^3 \times 6$ lattices with a tree-level Symanzik improved gauge action and a staggered Fermion sea quark action with two stout smearing steps and for a quark mass tuned to have the physical p ... More
Presented by Prof. Rajiv V GAVAI on 20/6/2017 at 15:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We propose a path modification method to evade the sign problem in the Monte-Carlo calculations for complex actions. Among many approaches to the sign problem, the Lefschetz-thimble path-integral method and the complex Langevin method are currently considered to be promising and extensively discussed. In these methods, real field variables are complexified and the integration manifold is determ ... More
Presented by Prof. Akira OHNISHI on 22/6/2017 at 15:40
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Ever since fast hydrodynamization has been observed in heavy ion collisions the understanding of the hot early out-of-equilibrium stage of such collisions has been a topic of intense research. We use the gauge/gravity duality to model the creation of a strongly coupled Quark-Gluon plasma in a non-conformal gauge theory. This numerical relativity study is the first non-conformal holographic simula ... More
Presented by Dr. Maximilian ATTEMS on 23/6/2017 at 15:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We present preliminary results f​or the phase diagram of​ effective Polyakov line actions​,​ derived from SU(3) lattice gauge theory with dynamical staggered quarks ​showing a​ line of​ ​phase transitions in the temperature-density plane. The derivation is via the method of relative weights​, the quark mass is 700 MeV,​ and the ​effective theories are solved at finite chemica ... More
Presented by Roman HÖLLWIESER on 21/6/2017 at 12:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study an RMT model for QCD at finite density using the Complex Langevin algorithm. Naive implementation of the algorithm shows convergence towards the phase quenched or quenched theory. A detailed analysis of this issue and a potential resolution of the failure of this algorithm are discussed. Among others we study the behavior of the real and imaginary parts of the action under Langevin evolu ... More
Presented by Dr. Savvas ZAFEIROPOULOS on 20/6/2017 at 18:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The phase boundary of lattice QCD for staggered fermions in the $\mu_B-T$ has been established via a dual representation in the strong coupling limit. Extending this phase boundary towards finite inverse gauge coupling is challenging. We present numerical simulations away from the strong coupling limit, taking into account the $O(\beta^2)$ corrections via plaquette occupation numbers. This allows ... More
Presented by Dr. Jangho KIM on 21/6/2017 at 13:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We investigate the properties of QCD at finite temperature and isospin chemical potential using 2+1 flavours of staggered fermions with physical quark masses. We provide updates for our results concerning the properties of the phase diagram in the approach to the continuum limit and the comparison to Taylor expansion. We also discuss our determination of the equation of state at finite isospin ch ... More
Presented by Dr. Bastian BRANDT on 20/6/2017 at 15:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We investigate a two-flavor quark system with opposite chemical potentials. Simulations of these isospin systems are not hindered by the sign problem. By introducing an auxiliary parameter, it is possible to simulate in the pion condensation phase by circumventing small eigenvalues of the Dirac operator. The obtained results can then be used to gain information about systems with nonzero bary ... More
Presented by Mr. Sebastian SCHMALZBAUER on 20/6/2017 at 15:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The equation of state (EoS) in 2+1 flavor QCD has recently been established in the continuum limit at the physical quark masses. The HotQCD collaboration result provides the EoS in the temperature range from 130 to 400 MeV. We extend the HotQCD equation of state to higher temperatures. We utilize the Highly Improved Staggered Quarks (HISQ) action. We perform computations at the pion mass of about ... More
Presented by Dr. Alexei BAZAVOV on 21/6/2017 at 12:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Lattice QCD, involving a large number of degrees of freedom, relies on the applicability of Monte Carlo methods. The presence of complex weights in the study of QCD at finite baryonic density, introduces the sign (or phase problem) in this context and is a mayor impediment for faster progress in this field. In addition to standard reweighting, several approaches have been tried to sort this ... More
Presented by Prof. Lorenzo Luis SALCEDO on 22/6/2017 at 18:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Nowadays GPU is used as main coprocessor to perform all mathematical operations inside numerical simulations of the lattice QCD. Using GPGPU techniques we developed the code to study QCD phase transition line in the canonical approach. The canonical approach is a powerful tool to investigate sign problem in LQCD. The central part of the canonical approach is the fugacity expansion of the grand ... More
Presented by Mr. Vladimir GOY on 23/6/2017 at 17:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We overview our results on hadron spectroscopy upon truncation of the near-zero modes of the overlap Dirac operator. A density of the near-zero modes is directly related to the quark condensate. Apriori their truncation should lead to SU(2)_L * SU(2)_R restoration. However a degeneracy that is larger than SU(2)_L*SU(2)_R*U(1)_A is observed. This symmetry turnes out to be SU(4) that includes ... More
Presented by Prof. Leonid GLOZMAN on 21/6/2017 at 12:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We present new results of full QCD at nonzero chemical potential. In PRD 92, 094516 (2015) the complex Langevin method was shown to break down when the inverse coupling decreases and enters the transition region from the deconfined to the confined phase. We found that the stochastic technique used to estimate the drift term can be very unstable for indefinite matrices. This may be avoided by using ... More
Presented by Dr. Jacques BLOCH on 20/6/2017 at 15:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Simulating thimble regularization of lattice field theory can be tricky when more than one thimble is to be taken into account. A couple of years ago we proposed a solution for this problem. More recently this solution proved to be effective in the case of 0+1 dimensional QCD. A few lessons we can learnt, including the role of symmetries and general hints on algorithmic solutions. We also p ... More
Presented by Prof. Francesco DI RENZO on 21/6/2017 at 8:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We discuss the canonical formulation of the Z(3) Potts model and its relation to heavy-dense QCD at fixed baryon number. By taking into account the local quark occupation numbers we construct a cluster algorithm which completely eliminates the fermion sign problem. In addition, the cluster formulation allows the construction of improved estimators for various observables such as the baryon chemica ... More
Presented by Dr. Urs WENGER on 22/6/2017 at 18:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these poin ... More
Presented by Mr. Tobias RINDLISBACHER on 22/6/2017 at 17:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
This report is devoted to the study of temperature dependence of bulk viscosity in SU(3)-gluodynamics. To calculate bulk viscosity wemeasured the correlation function of the trace anomaly for a set of temperatures in the region T/T_c \in (0.9, 1.5). We used multilevel algorithm which allowed us to improve the accuracy of the data. To extract the values of bulk viscosity we used two approaches: fit ... More
Presented by Dr. Victor BRAGUTA on 23/6/2017 at 16:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Effective Polyakov line actions are a powerful tool to study the finite temperature behaviour of lattice gauge theories. They are much simpler to simulate than the original (3+1) dimensional LGTs and are affected by a milder sign problem. However it is not clear to which extent they really capture the rich spectrum of the original theories, a feature which is instead of great importance if one ... More
Presented by Prof. Michele CASELLE on 21/6/2017 at 12:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We present results from our recent calculation of the QCD equation of state to $\mathcal{O}(\mu_B^6)$ in the baryon chemical potential $\mu_B$ using the method of Taylor expansions. Our calculations were carried out using the Highly Improved Staggered Quark action (HISQ). The strange quark mass was fixed to its physical value while the light quark mass was fixed at two values viz. $m_l/m_s=1/20$ ... More
Presented by Dr. Prasad HEGDE on 23/6/2017 at 18:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Jarzynski's equality provides an elegant and powerful tool to compute directly differences in free-energy in Monte Carlo simulations and it can be readily extended to lattice gauge theories to compute a large set of physically interesting observables. In this talk we present a novel technique to determine the thermodynamics of strongly-interacting matter based on this relation, which allows for a ... More
Presented by Mr. Alessandro NADA on 21/6/2017 at 7:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We extend our previous studies [PhysRevD.90.054509, PhysRevD.92.094510] of the pion quasiparticle in the low-temperature phase of two-flavor QCD with support from chiral effective theory. This includes the analysis performed on a finite temperature ensemble of size $20\times 64^3$ at $T\simeq 151$MeV and a lighter zero temperature pion mass $m\simeq 186$MeV. Furthermore, in our investigation of th ... More
Presented by Mr. Kai ZAPP on 22/6/2017 at 15:00
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
$SU (N)$ gauge theories on compact spaces have a non-trivial vacuum structure characterised by a countable set of topological sectors and their topological charge. In lattice simulations, every topological sector need to be explored a number of times which reflects its weight in the path integral. Current lattice simulations are impeded by the so-called freezing of the topological charge problem. ... More
Presented by Mr. Adrien FLORIO on 21/6/2017 at 7:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In this talk we report our study on the thermal modifications of charmonia and bottomonia from spatial correlation functions at zero and nonzero momenta in quenched QCD. To accommodate the heavy quarks on the lattice we performed simulations on very fine lattices at a fixed beta value corresponding to a lattice spacing $a^{-1}\sim$22 GeV on $192^3\times 32$, $192^3\times 48$, $192^3\times 64$ and ... More
Presented by Mr. Hai-Tao SHU on 19/6/2017 at 17:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We study the topological charge in $N_f=2$ QCD at finite temperature using Mobius domain-wall fermions. The susceptibility $\chi_t$ of the topological charge defined either by the index of overlap Dirac operator or a gluonic operator is investigated at several values of temperature $T\ (>T_c)$ varying the quark mass. A strong suppression of the susceptibility is observed below a certain value of t ... More
Presented by Yasumichi AOKI on 19/6/2017 at 14:50
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
The severe sign problem (SSP) is a longstanding challenge for high energy and solid-state theorists. In order to test new proposals to simulate physical systems with SSP it would be very useful to dispose of systems with SSP, and non trivial phase structure, the dynamics of which is well known. We study here the two-dimensional antiferromagnetic Ising model within an imaginary magnetic field, ... More
Presented by Eduardo ROYO-AMONDARAIN on 22/6/2017 at 18:10
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
Recently there has been remarkable progress in solving the sign problem, which occurs in investigating statistical systems with a complex weight. The two promising methods, the complex Langevin method and the Lefschetz thimble method, share the idea of complexifying the dynamical variables, but their relationship has not been clear. Here we propose a unified formulation, in which the sign problem ... More
Presented by Prof. Jun NISHIMURA on 21/6/2017 at 8:20
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
We report on the status of ongoing investigations aiming at: locating the deconfinement critical point with standard Wilson fermions and <I>N<sub>f</sub> = 2</i> flavors towards the continuum limit (standard Columbia plot); locating the tricritical masses at imaginary chemical potential with unimproved staggered fermions at <I>N<sub>f</sub> = 2</i> (extended Columbia plot); identifying the order o ... More
Presented by Francesca CUTERI on 23/6/2017 at 17:30
Type: Parallel Session: Nonzero Temperature and Density
Track: Nonzero Temperature and Density
In this report we study the properties of the dense SU(2) QCD. The lattice simulations are carried out with improved gauge action and smaller lattice spacing as compared to our previous work. This allowed us to approach closer to the continuum limit and reach larger densities without lattice artifacts. We measured string tension and Polyakov loop as functions of chemical potential and temperatur ... More
Presented by Mr. Aleksandr NIKOLAEV on 21/6/2017 at 11:30
Building timetable...