Name: Extreme QCD 2017 - The 15th international workshop on QCD in eXtreme conditions
Start: 2017-06-26T01:50:00+02:00
End: 2017-06-28T20:00:00+02:00
Location: No location set

Extreme QCD 2017 - The 15th international workshop on QCD in eXtreme conditions

from Monday 26 June 2017 (01:50) to Wednesday 28 June 2017 (20:00)

Monday 26 June 2017

08:30 Registration
Registration
08:30 - 09:00

09:00 Welcome and Introduction
Welcome and Introduction
09:00 - 09:20

09:20 Session Chair: Adriano Di Giacomo
Session Chair: Adriano Di Giacomo
09:20 - 09:20
The struggle against the sign problem - Philippe de Forcrand (ETH Zurich & CERN)
The struggle against the sign problem
- Philippe de Forcrand (ETH Zurich & CERN)
09:20 - 10:00
The 'sign problem', i.e. the presence of configurations with negative or complex weight in the partition sum, has been a technical obstacle of growing importance, which prevents the Monte Carlo study of many systems of physical interest, among them QCD in 'extreme' parameter regimes. I will recall some basic notions about the sign problem, and review current attempts to overcome it.
10:00 Thimble regularization 5 years later - Francesco Di Renzo (PR)
Thimble regularization 5 years later
- Francesco Di Renzo (PR)
10:00 - 10:25
The proposal of thimble regularization as a solution to the sign problem is by now 5 years old. A report on recent work done in Parma is presented. This includes progress in our algorithmic solutions, in particular with respect to cases in which multiple thimbles are to be taken into account. Very much related to this, the role of symmetries is discussed. Finally, an update on thimble simulations of gauge theories is presented.
10:25 Fermion bag approach to Hamiltonian lattice field theories - Shailesh Chandrasekharan (Duke University)
Fermion bag approach to Hamiltonian lattice field theories
- Shailesh Chandrasekharan (Duke University)
10:25 - 10:50
Hamiltonian lattice field theories provide an alternate approach to study traditional Lagrangian lattice field theories in the strongly interacting regime. These formulations are more commonly used in condensed matter physics and may be more natural in theories at finite densities. They can be formulated both in discrete and continuous time. In the continuous time formulation they can help in reducing the fermion doubling problem. Some new sign problems are also solvable within this approach. In the discrete time formulation they are very similar to traditional Lagrangian lattice field theories but with unconventional actions. Unfortunately, traditional Monte Carlo methods for Hamiltonian lattice field theories seem to scale rather poorly with system size. Here we show that by using ideas of fermion bags we can design algorithms that help speed up these calculations and allow us to go to large lattices for the first time. Using this approach we compute critical exponents of the 2+1d Gross-Neveu model with Nf=1, which was impossible so far in Lagrangian lattice field theory.
10:50 Canonical simulations of heavy-dense QCD without a sign problem - Urs Wenger (Institute for Theoretical Physics, University of Bern)
Canonical simulations of heavy-dense QCD without a sign problem
- Urs Wenger (Institute for Theoretical Physics, University of Bern)
10:50 - 11:15
In this talk I show how the canonical formulation of QCD can be obtained from transfer matrices defined directly in the canonical sectors of QCD. These transfer matrices are closely related to the dimensionally reduced Wilson fermion determinant and provide a complete temporal factorization of the fermion determinant. In the heavy-dense limit, the fermionic contributions to the canonical partition functions can be calculated analytically and I show that the sign problem is absent at infinitely strong coupling. Finally, I construct a cluster algorithm which solves the sign problem away from the strong coupling limit.
11:15 Coffee Break
Coffee Break
11:15 - 11:45
11:45 Canonical Approach for Exploring Finite Density QCD - Atsushi Nakamura (FEFU)
Canonical Approach for Exploring Finite Density QCD
- Atsushi Nakamura (FEFU)
11:45 - 12:10
Canonical approach is a way to map QCD at imaginary chemical potential regions to the real ones. The essential idea is simple: Z(¥mu,T) = ¥sum_n Z_n (exp(¥mu/T))^n, where Z_n, the canonical partition functions, do not depend on ¥mu. We construct Zn in the imaginary ¥mu regions, and we can calculate Z(¥mu,T) at any real ¥mu. Since Z_n drops very fastly as |n| increases, and we must fight against the overlap problem, we need several algorithmic and computational tricks, such as a multi-precision calculation. In Vladivostok, we have investigated the sources of unstable Z_n, and developed methods to overcome them. I will report these studies and the outcomes, especially those for comparison of heavy ion collision experiment.
Session Chair: Mariapaola Lombardo
Session Chair: Mariapaola Lombardo
11:45 - 11:45
12:10 The QCD sign problem and the effective Polyakov line action - Roman Höllwieser (VUT)
The QCD sign problem and the effective Polyakov line action
- Roman Höllwieser (VUT)
12:10 - 12:35
We suggest to solve the sign problem by mapping full QCD to an effective Polyakov line model. The method of relative weights, coupled with mean field theory, is applied to derive an effective action for an underlying SU(3) gauge theory with dynamical staggered fermions at finite densities. We present first results and discuss issues so far encountered.
12:35 Simulation of theories with a topological term - Eduardo Follana (Universidad de Zaragoza)
Simulation of theories with a topological term
- Eduardo Follana (Universidad de Zaragoza)
12:35 - 13:00
We discuss two methods for simulating systems with a "theta-like" term in the action, and that therefore suffer from a severe sign problem. Both methods are based on simulations at imaginary values of the "theta-like" parameter, where the sign problem is absent. We show the results of implementing the methods in a variety of physical systems, and we analyze their applicability and shortcomings. We also present preliminary results on the Schwinger model with a theta term, and we discuss the prospects for simulating QCD with a non-zero theta angle.
13:00 Patterns and Partners for chiral symmetry restoration - Ángel Gómez Nicola (Universidad Complutense Madrid)
Patterns and Partners for chiral symmetry restoration
- Ángel Gómez Nicola (Universidad Complutense Madrid)
13:00 - 13:25
The nature of chiral symmetry restoration and the identification of its correct pattern in terms of $O(4)$ and $U(1)_A$ restoration are central problems for our present understanding of the QCD phase diagram, which are not fully settled in lattice simulations. We will present a theoretical analysis based on Ward Identities which sheds light on this issue and where partner degeneration is systematically studied and connected with physical processes for the full scalar/pseudoscalar $U(3)$ meson nonets. Model-independent results are derived, which in addition allow to understand the temperature dependence of lattice screening masses through particular quark condensate combinations. Their realization in $U(3)$ Chiral perturbation Theory will also be described. Special attention will be paid to the role of the thermal $f_0(500)$ state to describe lattice data for the scalar susceptibility through thermal corrections to its pole parameters generated from unitarized pion scattering.
13:30 Lunch break
Lunch break
13:30 - 15:00
15:00 Holographic approaches to the study of strongly interacting matter in extreme conditions - Jorge Casalderrey Solana (University of Oxford)
Holographic approaches to the study of strongly interacting matter in extreme conditions
- Jorge Casalderrey Solana (University of Oxford)
15:00 - 15:40
The strong correlations observed in particle production in heavy ion collisions suggest strong interaction between the quarks and gluons that form the Quark Gluon Plasma. These interactions are so large that indicate that the QGP close to the deconfining transition may no be well approximated by a gas of quasiparticles. This has highlighted the need to develop new tools able to describe real-time processes in non-abelian gauge theory plasmas without quasiparticles. Holography provides such a tool. In this talk I will review recent theoretical and phenomenological results arising from the gauge/gravity duality that shed light on how strongly coupled plasma is produced, interacts and quenches energetic probes.
Session Chair: Mikhail Stephanov
Session Chair: Mikhail Stephanov
15:00 - 15:00
15:40 Inverse Magnetic Catalysis in Holographic QCD - Matti Jarvinen (Ecole Normale Superieure, Paris)
Inverse Magnetic Catalysis in Holographic QCD
- Matti Jarvinen (Ecole Normale Superieure, Paris)
15:40 - 16:05
Lattice simulations have shown recently that, contrary to earlier expectations, the chiral condensate is suppressed with growing magnetic field near the chiral and deconfinement transition temperatures of QCD, a phenomenon now known as “Inverse Magnetic Catalysis”. V-QCD is a holographic model for QCD, which fully includes the backreaction of the quarks to the gluonic degrees of freedom. I demonstrate that this holographic model reproduces the inverse magnetic catalysis, and provides a good qualitative match with lattice results for the condensate and related observables. In particular, the inverse catalysis is enhanced with increasing number of flavors, in agreement with lattice data. I will also comment on the predictions of the model at finite chemical potential and magnetic field.
16:05 Dense nuclear and quark matter in holographic QCD - Andreas Schmitt (University of Southampton)
Dense nuclear and quark matter in holographic QCD
- Andreas Schmitt (University of Southampton)
16:05 - 16:30
Dense matter in the core of neutron stars is strongly coupled and presents an enormous theoretical challenge. First-principle methods from QCD are currently known only for vanishing or asymptotically large baryon densities, while phenomenological models are usually restricted to either nuclear or quark matter and/or contain many unknown parameters. I will discuss whether and how holographic methods can help. In particular, I will present latest work on nuclear matter and the chiral phase transition to quark matter in the Sakai-Sugimoto model, potentially leading to a strongly coupled equation of state with only 3 parameters that is applicable over a wide density regime.
16:30 Fast Hydrodynamization of Non-conformal Holographic Shockwaves - Maximilian Attems (University of Barcelona)
Fast Hydrodynamization of Non-conformal Holographic Shockwaves
- Maximilian Attems (University of Barcelona)
16:30 - 16:55
Ever since fast hydrodynamization has been observed in heavy ion collisions the understanding of the 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 simulation of a heavy ion collision and reveals the existence of new relaxation channels due to the presence of non-vanishing bulk viscosity. We study collisions at different energies in gauge theories with different degrees of non-conformality and compare three relaxation times which can occur in different orderings: the hydrodynamization time (when hydrodynamics becomes applicable), the EoSization time (when the average pressure approaches its equilibrium value) and the condensate relaxation time (when the expectation value of a scalar operator approaches its equilibrium value). We find that these processes can occur in several different orderings. Finally, I will discuss a new example of the applicability of hydrodynamics to systems with large gradients. We show that the time evolution and saturation of the spinodal instability (corresponding to black branes afflicted by the Gregory-Laflamme instability in the gravity dual) are accurately described by second-order hydrodynamics, where a set of locally unstable states with a first-order thermal phase transition settle down to a static, inhomogeneous configuration.
16:55 Thermal entropic destruction of quark-antiquark pair from dynamical holographic QCD - Subhash Mahapatra (KU Leuven)
Thermal entropic destruction of quark-antiquark pair from dynamical holographic QCD
- Subhash Mahapatra (KU Leuven)
16:55 - 17:20
Lattice QCD results indicate a large amount of entropy associated with the quark-antiquark pair near the deconfinement temperature. The lattice data show a sharp peak in the quark-antiquark entropy near the transition temperature. Further, this entropy increases with inter quark distances. In this work, we used the gauge/gravity duality to reproduce these lattice results. For this purpose, we consider a phenomenological bottom-up Einstein-Maxwell-dilaton gravity model and analytically construct the black hole solutions whose dual boundary theories satisfy the properties of confinement as well as deconfinment. We study the entropy of the quark-antiquark pair in confinement/deconfiment phases and find that our holographic model qualitatively reproduces the corresponding lattice results for the entropy. We further provide holographic results with chemical potential
17:20
17:20 - 20:00
Contributions

17:20 Correlation function of energy-momentum tensor in SU(3) gauge theory from gradient flow - Masakiyo Kitazawa (Osaka University)

17:20 Color screening masses under the influence of strong background fields - Andrea Rucci (PI)

17:20 A way to avoid the global sign problem by modifying the Lefschetz thimble method - Takahiro Doi (Quantum Hadron Physics Laboratory Theoretical Research Division, Nishina Center, RIKEN)

17:20 Flux Tubes in QCD across deconfinement - Francesca Cuteri (Goethe Universität - Frankfurt am Main)

17:20 Cumulants of the quark number fluctuations from LQCD at imaginary potentials - Francesco Sanfilippo (INFN - Sezione Roma III)

17:20 $SU(2N_F)$-Ward identities for QCD with restored chiral symmetry - Vasily Sazonov (LPT Orsay, Université Paris-Sud)

17:20 Curvature of the pseudo-critical line in QCD: comparison of analytic continuation and Taylor expansion methods - Kevin Zambello (P)

17:20 Сonfinement-deconfinement transition in dense two-color QCD - Aleksandr Nikolaev (ITEP & FEFU)

17:20 Fate of quarkonium in a quark gluon plasma via a Lindblad equation - Davide De Boni (Swansea University)

17:20 Gluon and ghost correlation functions of 2-color QCD at finite density - Ouraman Hajizadeh (University of Graz)

17:20 Accurate Simulation of the Finite Density Thirring Model - Jarno Rantaharju (Duke University)

17:20 Reweighted complex Langevin approach to chiral fermion models at finite density - Hirotsugu Fujii (U Tokyo)

17:20 Calculation of $B_{K}$ with Wilson fermion using gradient flow - Asobu Suzuki (University of Tsukuba)

17:20 Charged pion condensation in chiral asymmetric dense quark matter in the framework of a (1+1) NJL_2 model - Tamaz Khunjua (Moscow State University M.V. Lomonosov)

17:20 Topological susceptibility and Gribov copies - Caroline Felix (KU Leuven)

17:20 Lattice study of continuity and finite-temperature transition in $2d$ $SU(N) \times SU(N)$ Principal Chiral Model - Semen Valgushev (Regensburg University)

17:20 Complex Langevin simulations of a finite density model for QCD - Savvas Zafeiropoulos (College of William & Mary and Jefferson Lab)

17:20 Dispersion relations of charged and uncharged pions in presence of weak magnetic field - Souvik Priyam Adhya (Post doctoral fellow)

17:20 Alternatives to the stochastic "noise vector" approach - Benjamin Jaeger (ETH Zurich)

17:20 Compactified gauge theories under extreme conditions - Mohamed Anber (Lewis & Clark College)

17:20 General equilibrium second-order hydrodynamic coefficients for quantum fields - Matteo Buzzegoli (FI)

17:20 Flux tubes in Nf=2+1 QCD with magnetic fields - Francesco Negro (PI)

17:20 Investigating Columbia plot with clover fermions - Yoshifumi Nakamura (RIKEN)
Tuesday 27 June 2017
09:00 Recent results on QCD thermodynamics from Lattice - Sayantan Sharma (Tata Institute of Fundamental Research)
Recent results on QCD thermodynamics from Lattice
- Sayantan Sharma (Tata Institute of Fundamental Research)
09:00 - 09:40
Fluctuations of conserved charges like baryon number and strangeness are important observables to understand the nature and interactions between the degrees of freedom in different phases of QCD. The higher order fluctuations are particularly important to get information on the location of possible QCD critical end-point and to understand the interplay between fluctuations and non-trivial topological properties in QCD. In this talk I will highlight the recent theoretical and algorithmic developments made in lattice gauge theory in calculating the higher moments of conserved charges. I will also discuss how the lattice data on fluctuations and correlations of different conserved charges could be used for determining the QCD equation of state at finite density, to constraint the possible location of critical end-point in the QCD phase diagram and understand the nature and interactions among quasi-particles across the chiral crossover transition in QCD.
Session Chair: Michael Ilgenfritz
Session Chair: Michael Ilgenfritz
09:00 - 09:00
09:40 Strange baryons below and above the deconfinement transition - Gert Aarts (Swansea University)
Strange baryons below and above the deconfinement transition
- Gert Aarts (Swansea University)
09:40 - 10:05
We investigate the fate of strange baryons in the hadronic gas and the quark-gluon plasma. In the confined phase a strong temperature dependence is seen in the masses of the negative-parity groundstates, while at high temperature parity doubling emerges. We study baryons with different strangeness and find a noticeable effect of the heavier s quark. This study uses nonperturbative lattice simulations, employing the FASTSUM anisotropic Nf = 2 + 1 ensembles.
10:05 Determination of deconfinement transition from Roberge-Weiss periodicity - Kouji Kashiwa (Yukawa Institute for Theoretical Physics, Kyoto University)
Determination of deconfinement transition from Roberge-Weiss periodicity
- Kouji Kashiwa (Yukawa Institute for Theoretical Physics, Kyoto University)
10:05 - 10:30
In this talk, I will report recent progress of our study on the confinement-deconfinement transition in QCD from topological view points. We have proposed a new determination of the confinement-deconfinement transition by using the imaginary chemical potential. The imaginary chemical potential can be interpreted as the Aharonov-Bohm phase and then an analogy of the topological order suggests that the Roberge-Weiss endpoint would define the deconfinement temperature. Based on the topological property, we can construct a new quantity which describes the confinement-deconfinement transition. This quantity is defined as the integral of the quark number susceptibility along the closed loop of the dimensionless imaginary chemical potential.
10:30 The QCD phase transition at large N as BKT type transition. - Ariel Zhitnitsky (University of British Columbia)
The QCD phase transition at large N as BKT type transition.
- Ariel Zhitnitsky (University of British Columbia)
10:30 - 10:55
We conjecture that the phase transitions in QCD at large N is triggered by the drastic changes in the instanton density, and corresponding drastic modification of the \theta behaviour in the system. We advocate the picture that these very sharp changes is a result of complete reconstruction of the relevant Euclidean configurations when the instantons at large T ``dissociate" into N fractionally charged constituents (the instanton quarks, the instanton -dyons, the instanton-monopoles, you name it) at small T. This picture is quite universal and describes the corresponding transitions in different circumstances. In particular, the transition to colour superconducting phase at \mu>\mu_c, or to the conformal phase (for sufficiently large N_f/N) can be described using the same universal framework. The talk is based on few recent papers (see [1] and references therein) and some recent development. [1]. A. Zhitnitsky ``Conformal window in QCD for large numbers of colours and flavours,'' Nucl.\ Phys.\ A {\bf 921}, 1 (2014), arXiv:1308.0020 [hep-ph].
10:55 Coffee break
Coffee break
10:55 - 11:25

11:25 Session Chair: Francesco Di Renzo
Session Chair: Francesco Di Renzo
11:25 - 11:25
Taylor series expansions for higher order cumulants - Frithjof Karsch (Brookhaven National Laboratory)
Taylor series expansions for higher order cumulants
- Frithjof Karsch (Brookhaven National Laboratory)
11:25 - 11:50
We present results on Taylor series expansions for up to fourth order cumulants of conserved charge fluctuations, construct expansions for ratios of these cumulants and discuss their application to the analysis of freeze-out conditions in heavy ion experiments. Our results are based on lattice QCD calculations performed with the HISQ action and quark masses tuned to their physical values.
11:50 QCD thermodynamics. Hard-thermal-loop perturbation theory vs lattice - Jens Oluf Andersen (NTNU)
QCD thermodynamics. Hard-thermal-loop perturbation theory vs lattice
- Jens Oluf Andersen (NTNU)
11:50 - 12:15
The perturbative series for finite-temperature field theories has very poor convergence properties and one needs a way to reorganize it. In this talk, I review one way of reorganizing the perturbative series thermal QCD, namely hard-thermal-loop perturbation theory (HTLpt). I will present results for the pressure, trace anomaly, speed of sound and the quark susceptibilities from a 3-loop HTLpt calculation. A careful comparison with available lattice data shows good agreement for a number of physical quantities.
12:15 Scale invariant resummed perturbation at finite temperature - Jean-Loic Kneur (Lab. Charles Coulomb (L2C) Montpellier)
Scale invariant resummed perturbation at finite temperature
- Jean-Loic Kneur (Lab. Charles Coulomb (L2C) Montpellier)
12:15 - 12:40
We will illustrate how our recently developed renormalization group optimized perturbation (RGOPT) efficiently resums perturbative expansions in thermal field theories. The resulting convergence and scale dependence of optimized thermodynamical quantities are drastically improved as compared to standard perturbative expansions, as well as compared to other related methods such as the screened perturbation or (resummed) hard-thermal-loop perturbation. Our general method will be illustrated for the nonlinear sigma model, as a toy model for thermal QCD, and we will also discuss application of RGOPT to hard thermal loop resummation for QCD thermodynamical quantities.
12:40 Diagrammatic Monte-Carlo for large-N non-Abelian lattice field theories based on the convergent weak-coupling expansion - Pavel Buividovich (Regensburg University)
Diagrammatic Monte-Carlo for large-N non-Abelian lattice field theories based on the convergent weak-coupling expansion
- Pavel Buividovich (Regensburg University)
12:40 - 13:05
We demonstrate that non-Abelian lattice field theories such as principal chiral model and pure lattice gauge theory in the large-N limit admit infrared-finite weak-coupling expansion in powers of coupling and logs of coupling, reminiscent of re-summed series in thermal field theory and resurgent trans-series without exponential terms. Such a double-series structure arises due to the bare mass term proportional to the coupling constant, which stems from the Jacobian in the path integral measure and is absent in the scale-invariant classical action. This term renders the perturbative expansion infrared-finite even for an infinite lattice size, which allows to sample it using Diagrammatic Monte-Carlo. On the exactly solvable example we demonstrate that this expansion incorporates the non-perturbative mass gap. We then develop a DiagMC algorithm for sampling planar diagrams in the principal chiral model and numerically demonstrate the convergence of our expansion for up to 12 leading orders, which is the practical limit set by the increasingly strong sign problem at high orders. We find reasonably good agreement with conventional Monte-Carlo, extrapolated to infinite N. Finally, we comment on the applicability of our approach to planar QCD at zero and finite density.
13:05 Lunch break
Lunch break
13:05 - 14:50
14:50 Chiral effects in strong magnetic backgrounds: from QCD to condensed matter physics - Igor Shovkovy (Arizona State University)
Chiral effects in strong magnetic backgrounds: from QCD to condensed matter physics
- Igor Shovkovy (Arizona State University)
14:50 - 15:30
Chiral symmetry and its breaking play a profound role in the theory of strong interactions. Over the years, numerous advances have been made in understanding the dynamics responsible for chiral symmetry breaking in vacuum and its restoration at high temperatures. One of the instructive tools in studying the underlying physics is a strong background magnetic field. On the one hand, such a field acts as a catalyst by helping the symmetry breaking via the dimensional reduction and an increased density of low-energy states. On the other, the confinement is eroded by an enhanced screening from the low-energy states in the strong magnetic field. The outcome is a subtle interplay between the two competing dynamics that I will attempt to review. I will also discuss the recent advances in pseudo-relativistic condensed matter systems, in which chirality plays an equally important role and a number of interesting phenomena could be realized in the presence of strong magnetic fields.
Session Chair: Andreas Schmitt
Session Chair: Andreas Schmitt
14:50 - 14:50
15:30 Lattice simulation of Chiral Magnetic Effect in Dirac Semimetals - Andrey Kotov (Institute for Theoretical and Experimental Physics)
Lattice simulation of Chiral Magnetic Effect in Dirac Semimetals
- Andrey Kotov (Institute for Theoretical and Experimental Physics)
15:30 - 15:55
Recently discovered Dirac Semimetals Na3Bi and Cd3As2 provide perfect opportunity for investigation of phenomena which were usually attibuted to high energy physics. The reason for this is the existence of two massless Dirac fermions in the quasi-particle dispersion relation for these materials. One of the manifestations of the chiral anomaly, Chiral Magnetic Effect, can be be observed in these materials as a large magnetoconductivity. We study the conductivity of these materials in external magnetic field within lattice effective field theory approach. Our results confirm the existence of Chiral Magnetic Effect in Dirac Semimetals.
15:55 Landau levels in lattice QCD in an external magnetic field - Matteo Giordano (Eotvos University)
Landau levels in lattice QCD in an external magnetic field
- Matteo Giordano (Eotvos University)
15:55 - 16:20
I will discuss the issue of Landau levels of quarks in lattice QCD in an external magnetic field. In two dimensions the lowest Landau level can be identified unambiguously even if the strong interactions are turned on. This allows to define a "lowest Landau level" also in the four-dimensional case. It is then possible to study to what extent the effect of a magnetic field on observables can be explained in terms of the lowest Landau level, and test the validity of low-energy models of QCD that make use of the lowest-Landau-level approximation.
16:20 Chiral phase transition of three flavor QCD with nonzero magnetic field - Akio Tomiya (CCNU)
Chiral phase transition of three flavor QCD with nonzero magnetic field
- Akio Tomiya (CCNU)
16:20 - 16:45
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 staggered fermions and the plaquette action with spatial sizes $N_s$ = 16 and 24 and a fixed temporal size $N_t$ = 4. The value of the quark mass was chosen such that the system undergoes a first order chiral phase transition with zero magnetic field. We find that the quark chiral condensate undergoes magnetic catalysis in the whole temperature region, and the first order phase transition becomes stronger as magnetic field increases. The underlying mechanism will also be discussed.
16:45 Coffee Break
Coffee Break
16:45 - 17:15
17:15 Effects of magnetic field on the plasma evolution in relativistic heavy ion collisions - Shreyansh Shankar Dave (Institute of Physics)
Effects of magnetic field on the plasma evolution in relativistic heavy ion collisions
- Shreyansh Shankar Dave (Institute of Physics)
17:15 - 17:40
Very strong magnetic fields can arise in noncentral heavyion collisions at ultra relativistic energies, which may not decay quickly in a conducting plasma. We carry out relativistic magnetohydrodynamics (RMHD) simulations to study the effects of this magnetic field on the evolution of the plasma and on resulting flow fluctuations in the ideal RMHD limit. Our results show that magnetic field leads to enhancement in elliptic flow, though in general effects of magnetic field on elliptic flow are very complex. Interestingly, we find that magnetic field in localized regions can temporarily increase in time as evolving plasma energy density fluctuations lead to reorganization of magnetic flux. This can have important effects on chiral magnetic effect. Magnetic field has nontrivial effects on the power spectrum of flow fluctuations. For very strong magnetic field case one sees a pattern of evenodd difference in the power spectrum of flow coefficients arising from reflection symmetry about the magnetic field direction if initial state fluctuations are not dominant. We discuss the situation of nontrivial magnetic field configurations arising from collision of deformed nuclei and show that it can lead to anomalous elliptic flow. Special (crossed bodybody) configurations of deformed nuclei collision can lead to presence of quadrupolar magnetic field which can have very important effects on the rapidity dependence of transverse expansion (similar to beam focusing from quadrupole fields in accelerators). We also show the possibility of the dynamo like effects in the presence of (CFL) superfluid vortex (which may arise in low energy collisions experiments e.g. FAIR and NICA) in our RMHD simulations.
Session Chair: Ariel Zhitnitsky
Session Chair: Ariel Zhitnitsky
17:15 - 17:15
17:40 QED and QCD with massless fermions in three dimensions - Rajamani Narayanan (Florida International University)
QED and QCD with massless fermions in three dimensions
- Rajamani Narayanan (Florida International University)
17:40 - 18:05
Recent numerical results on QED and QCD with massless fermions in three dimensions will be presented. The main focus will be classifying theories as conformal or non-conformal. Results for the absence or presence of bilinear condensates will be presented using the behavior of low lying eigenvalues. Correlation functions of fermion bilinears will also be presented.
18:05 Phase structure of large-N gauge theory at finite temperature - Hiromichi Nishimura (BNL)
Phase structure of large-N gauge theory at finite temperature
- Hiromichi Nishimura (BNL)
18:05 - 18:30
We use a semiclassical method to analyze the phase structure of SU(N) gauge theory at infinite N in the presence of the external field. The effective potential can be written in terms of a Landau free energy for Polyakov loops, and we construct it using the perturbative contribution and a double trace deformation as the unknown confining potential. We show that there is a surface of a continuous phase transition analogous to the Gross-Witten-Wadia transition, whose boundary terminates at a tricritical point of a critical first-order phase transition. Depending on the confining potential we have considered, it gives rise to a third, fourth, or fifth-order phase transition in the Ehrenfest classification. Because the specific heat and the eigenvalue distribution of the Polyakov loop are sensitive to the confining potential, we argue that lattice simulations for large N could probe the order of phase transition as well as the form of the confining potential in any 1+d dimensions.
20:00 Social Dinner
Social Dinner
20:00 - 22:00
Wednesday 28 June 2017

09:00 Session Chair: Frithjof Karsch
Session Chair: Frithjof Karsch
09:00 - 09:00
Strongly interacting matter in extreme conditions: insights from hydrodynamic modeling of heavy ion collisions - Wojciech Florkowski (UJK Kielce / IFJ PAN Krakow)
Strongly interacting matter in extreme conditions: insights from hydrodynamic modeling of heavy ion collisions
- Wojciech Florkowski (UJK Kielce / IFJ PAN Krakow)
09:00 - 09:40
I the first part of the talk I will review several physics features of strongly interacting matter (such as, for example, equation of state and kinetic coefficients) that have been established by comparing heavy-ion data with hydrodynamic models. Then I will turn to the general problems of applicability of relativistic viscous hydrodynamics, in particular, for description of the early stages of heavy-ion collisions. Finally, I will turn to observables connected with polarization of the observed particles and comment on recent developments of relativistic fluid hydrodynamics with spin.
09:40 QCD Critical Point and Hydrodynamics - Mikhail Stephanov (UIC)
QCD Critical Point and Hydrodynamics
- Mikhail Stephanov (UIC)
09:40 - 10:05
I shall discuss the physics of fluctuations near the QCD critical point and application of hydrodynamics in the critical regime.
10:05 Quasiparticle anisotropic hydrodynamics for ultrarelativistic heavy-ion collisions - Mubarak Alqahtani (Kent State University)
Quasiparticle anisotropic hydrodynamics for ultrarelativistic heavy-ion collisions
- Mubarak Alqahtani (Kent State University)
10:05 - 10:30
We present the first comparisons of experimental data with phenomenological results from 3+1d quasiparticle anisotropic hydrodynamics (aHydroQP). We compare charged-hadron multiplicity, identified-particle spectra, identified-particle average transverse momentum, charged-particle elliptic flow, and identified-particle elliptic flow produced in LHC 2.76 TeV Pb+Pb collisions. The dynamical equations used for the hydrodynamic stage utilize non-conformal aHydroQP. The resulting aHydroQP framework naturally includes both shear and bulk viscous effects in addition to higher-order non-linear transport coefficients. The 3+1d aHydroQP evolution obtained is self-consistently converted to hadrons using anisotropic Cooper-Frye freezeout performed on a fixed-energy-density hypersurface. The final production and decays of the primordial hadrons are modeled using a customized version of THERMINATOR 2. In this first study, we utilized smooth Glauber-type initial conditions and a single effective freeze-out temperature $T_{\rm FO} = 130$ MeV with all hadronic species in full chemical equilibrium. With this rather simple setup, we find a very good description of many heavy-ion observables.
10:30 Collective Excitations in QCD Plasma - Ali Davody (Institute of Theoretical Physics, Regensburg University, 93040 Regensburg, Germany)
Collective Excitations in QCD Plasma
- Ali Davody (Institute of Theoretical Physics, Regensburg University, 93040 Regensburg, Germany)
10:30 - 10:55
We study the long wavelength excitations in rotating QCD fluid coupled to an external magnetic field at finite vector and axial charge densities. We first find the generalization of the both well-known Chiral Magnetic Wave (CMW) and Chiral Vortical Wave (CVW), separately. It turns out that at µ5 = 0 and in the absence of rotation, there exist two CMWs which propagate in the same and in the opposite directions of the magnetic field with the same velocities. However when µ5 6= 0, one of the CMW modes propagates faster than the other and additionally, they do not necessarily propagate in the opposite directions. The similar situation happens for the two CVWs in the rotating fluid at finite axial chemical potential. We then show that in general, when the fluid is either rotating and is coupled to a magnetic field, the CMW and the CVW mix with each other and make the Chiral Magnetic-Vortical Wave (CMVW). The resultant coupled waves have generally different velocities compared to the sum of velocities of the individual waves. We also find another excitation in the QCD plasma; the so-called Chiral Alfv´en Wave (CAW), an analogue of what as recently found in a chiral fluid with single chirality. We specifically show that in contrast to the latter case, the CAWs in QCD fluid may propagate only when both the vector and axial charge densities are non-vanishing. Furthermore, while the velocity of CAWs in a chiral fluid with single chirality depends on the coefficient of a gravitational anomaly, we show that in QCD fluid, it depends on the coefficients of both chiral and gravitational anomalies.
10:55 Coffee break
Coffee break
10:55 - 11:25
11:25 Finite temperature gluon spectral functions from twisted mass lattice QCD - Ernst-Michael Ilgenfritz (JINR, BLTP)
Finite temperature gluon spectral functions from twisted mass lattice QCD
- Ernst-Michael Ilgenfritz (JINR, BLTP)
11:25 - 11:50
I will report on an attempt to fix the gluon spectral functions at finite temperature in Landau gauge. Our study used a novel Bayesiann approach for the extraction of non-positive definite spectral functions. The spectral functions are extracted at three different lattice spacing. For each of them, a scan of temperatures around the crossover transition is carried out. There are indications for the existence of a well defined quasi-particle peak. Due to a relatively small number of imaginary frequencies available, we focus on the momentum and temperature dependence of the peak position while the width is beyond our present possibilities. The dispersion relation reveals different in-medium masses for longitudinal and transversal gluons at high temperatures, in agreement with weak coupling expectations.
Session Chair: Gert Aarts
Session Chair: Gert Aarts
11:25 - 11:25
11:50 Momentum anisotropy effects for quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature - Simone Biondini (Albert Einstein Center, Institute for Theoretical Physics - Uni Bern)
Momentum anisotropy effects for quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature
- Simone Biondini (Albert Einstein Center, Institute for Theoretical Physics - Uni Bern)
11:50 - 12:15
In the early stages of heavy-ion collisions, the hot QCD matter expands more longitudinally than transversely. This imbalance causes the system to become rapidly colder in the longitudinal direction and a local momentum anisotropy appears. In this talk we study the heavy-quarkonium spectrum in the presence of a small plasma anisotropy. We work in the framework of potential non-relativistic QCD at finite temperature. We inspect arrangements of non-relativistic and thermal scales complementary to those considered in the literature. In particular, we consider temperatures larger and Debye masses smaller than the binding energy, which is a temperature range relevant for presently running LHC experiments. In this setting we compute the leading thermal corrections to the binding energy and the thermal width induced by quarkonium gluo-dissociation
12:15 Thermal Sommerfeld effect for P-wave quarkonium in lattice NRQCD - Seyong Kim (Sejong University)
Thermal Sommerfeld effect for P-wave quarkonium in lattice NRQCD
- Seyong Kim (Sejong University)
12:15 - 12:40
Annihilation of heavy particles in thermal environment (e.g., quarkonium decay in Quark-Gluon Plasma and heavy dark matter particle annihilation in early universe) is influenced by long distance non-perturbative effect because multple exchanges of light particle between slow-moving incoming heavy particle is possible. Previously, we found that the existence of bound states in thermal QCD can lead to large enhancement for S-wave pair annihilation of heavy quark and heavy anti-quark in QGP by lattice NRQCD measurement. We continue our study of thermally averaged Sommerfeld factor, and here we report on our recent lattice calculation of the Sommerfeld factor for P-wave channel.
12:40 Quarkonium spectral functions at finite temperature on large quenched lattices and towards the continuum limit - Hiroshi Ohno (University of Tsukuba)
Quarkonium spectral functions at finite temperature on large quenched lattices and towards the continuum limit
- Hiroshi Ohno (University of Tsukuba)
12:40 - 13:05
We present our recent studies about quarkonium spectral functions in lattice QCD at finite temperature. We performed lattice QCD simulations with the quenched approximation on very large and fine lattices. We calculated quarkonium correlation functions in a quark mass range between charm and bottom quarks at temperatures between 0.75$T_c$ and 2.2$T_c$. Using the correlation functions for our finest lattice with lattice spacing $a^-1$ = 22 GeV, we reconstructed spectral functions, where we employed the conventional maximum entropy method as well as the stochastic methods to check systematic uncertainties. In this talk we discuss dissociation temperatures for charmonia and bottomonia and also show some estimates of the heavy quark diffusion coefficient. In addition, we show some results on a continuum extrapolation of the quarkonium correlation functions, which has been done for the first time, towards the continuum limit of the spectral functions.
13:05 Lunch Break
Lunch Break
13:05 - 14:30
14:30 Constraints on extreme density matter from GW observa- tion of neutron star mergers - Sebastiano Bernuzzi (PR)
Constraints on extreme density matter from GW observa- tion of neutron star mergers
- Sebastiano Bernuzzi (PR)
14:30 - 15:10
Neutron stars in binary systems are among the strongest sources of gravitational waves and among the main targets for ground-based gravitational-wave interferometers Advanced LIGO and Virgo. The observation of these events in the gravitational-wave window can provide us with unique information on neutron stars' masses, radii, and spins, including the possibility to set strong constraints on the unknown equation of state of matter at supranuclear densities. A crucial and necessary step for the development of gravitational-wave astronomy with these sources is the precise knowledge of the dynamics of the sources and of the emitted waveforms. I will talk about recent developments on the modeling of gravitational waves from neutron star mergers using numerical simulations in general relativity, focusing on how these observations can constrain extreme density matter.
Session Chair: Ignazio Bombaci
Session Chair: Ignazio Bombaci
14:30 - 14:30
15:10 New dynamic critical phenomena in nuclear and quark superfluids - Noriyuki Sogabe (Keio University)
New dynamic critical phenomena in nuclear and quark superfluids
- Noriyuki Sogabe (Keio University)
15:10 - 15:35
We study the static and dynamic critical phenomena near the possible high-density QCD critical point in the superfluid phase of nuclear and quark matter. In particular, we find that its dynamic universality class is different from those studied in QCD and condensed matter systems so far. We argue that this novelty stems from the interplay between the chiral criticality and the presence of the superfluid phonon---a feature specific for high-density QCD critical point.
15:35 Neutral pion matter in strong magnetic fields - Tomas Brauner (University of Stavanger)
Neutral pion matter in strong magnetic fields
- Tomas Brauner (University of Stavanger)
15:35 - 16:00
The ground state of QCD in sufficiently strong external magnetic fields and at moderate baryon chemical potential is a chiral soliton lattice (CSL) of neutral pions. This is a model-independent result based on low-energy effective field theory, and the magnetic fields and baryon densities required may occur in the cores of neutron stars. The spectrum of excitations above the CSL ground state contains a soft, nonrelativistic mode that gives an anomalous contribution to pressure, scaling with temperature and magnetic field as $T^{5/2}B^{3/2}$. Finally, I will argue that in stronger but still achievable magnetic fields, the neutral pion CSL background may catalyze Bose-Einstein condensation of charged pions.
16:00 Coffee Break
Coffee Break
16:00 - 16:30

16:30 Session Chair: Atsushi Nakamura
Session Chair: Atsushi Nakamura
16:30 - 16:30
Temperature dependence of bulk viscosity in SU(3)-gluodynamics - Victor Braguta (ITEP)
Temperature dependence of bulk viscosity in SU(3)-gluodynamics
- Victor Braguta (ITEP)
16:30 - 16:55
This report is devoted to the study of temperature dependence of bulk viscosity in SU(3)-gluodynamics. To calculate bulk viscosity we measured 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: fitting of the data by physically motivated ansatz and the Backus-Gilbert method.
16:55 Energy-momentum tensor correlation function in Nf=2+1 full QCD at finite temperature - Yusuke Taniguchi (University of Tsukuba)
Energy-momentum tensor correlation function in Nf=2+1 full QCD at finite temperature
- Yusuke Taniguchi (University of Tsukuba)
16:55 - 17:20
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 temperature region $174\le T\le697$ MeV. The ud quark mass is rather heavy with $m_{\pi}/m_{\rho}\simeq0.63$ while the s quark mass is set to approximately its physical value.
17:20 Thermodynamics of QCD at physical point with (2+1)-flavors of improved Wilson quarks using gradient flow - Kazuyuki Kanaya (University of Tsukuba)
Thermodynamics of QCD at physical point with (2+1)-flavors of improved Wilson quarks using gradient flow
- Kazuyuki Kanaya (University of Tsukuba)
17:20 - 17:45
The energy-momentum tensor and the chiral condensate are studied in (2+1)-flavor QCD with improved Wilson quarks 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 and perform finite-temperature simulations in the range $T \simeq 155$-544 MeV ($N_t = 4$-14 including odd numbers) at $a \simeq 0.09$ fm based on the fixed-scale approach using zero-temperature physical point configurations generated by the PACS-CS Collaboration. We present preliminary results on the equation of state and the chiral condensate obtained so far.
18:00 Pisa Raining Hour
Pisa Raining Hour
18:00 - 20:00

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