SCIENCE BRINGS NATIONS TOGETHER III International Workshop "Lattice and Functional Techniques for QCD"

10 Oct 2022, 09:30 → 14 Oct 2022, 19:00 Europe/Moscow

EIMI, St. Petersburg

The Joint Institute for Nuclear Research (JINR) and St Petersburg University (SPbU) organize the III International Workshop "Lattice and Functional Techniques for QCD". This year the Workshop will be held as a satellite event of The VII International Conference Models in Quantum Field Theory dedicated to the 82-th anniversary of professor A.N.Vasiliev (1940-2006) and 80th anniversary of professor V.D.Lyakhovsky (1942-2020) in Saint Petersburg, October 10 - 14, 2022.

Inspired by the activities going on in Dubna for the construction of NICA and the preparations of experimentalists for the BM@N and MPD experiments, the Bogoliubov Laboratory for Theoretical Physics of JINR realizes the project "Theory of Hadronic Matter under Extreme Conditions".

This Workshop is the third meeting specifically devoted to the functional and lattice QCD methods in the series of workshops and seminars in support of the project "Theory of Hadronic Matter under Extreme Conditions". It aims at bringing together practitioners of QCD lattice thermodynamics with specialists developing functional continuum approaches and to chart promising areas of collaboration or to continue already ongoing collaboration, mainly with the aim to extend the abilities of functional QFT methods and lattice QCD simulations:

• Properties of strongly interacting theories;
• QCD at finite temperature and density;
• The sign problem in lattice QCD;
• QCD in external fields;
• Transport properties of QCD;
• Topology in gauge theories;
• QCD phase transitions;
• Properties of the Quark-Gluon Plasma.

 

Organizing committee:

V. Braguta (BLTP JINR) — co-chairman
M. Hnatič (BLTP JINR & Univ. Košice) — co-chairman
G. Kalagov (BLTP JINR)
N. Lebedev (BLTP JINR)
S. Nedelko (BLTP JINR)
D. Sychev (BLTP JINR, MIPT)
A. Roenko (BLTP JINR) — scientific secretary
V. Voronin (BLTP JINR) — scientific secretary
O. Belova (JINR) — secretary

Monday 10 October

Registration

10:00 MQFT Plenary session

10:45 Coffee break

11:15 MQFT Plenary session

13:00 Lunch

14:45 MQFT Parallel sessions

16:15 Coffee break

16:45 MQFT Parallel sessions

18:30 Welcome party

Tuesday 11 October

10:00 MQFT Plenary session

10:45 Coffee break

11:15 MQFT Plenary session

12:45 Lunch

14:30 MQFT Parallel sessions

16:15 Coffee break

16:45 MQFT Parallel sessions

Wednesday 12 October

LFTQCD Session

1 Monopoles, instantons, and eta-prime meson in external magnetic fields

Magnetic monopoles are essential ingredients for explaining the color confinement mechanism, and instantons induce chiral symmetry breaking. The magnetic monopoles and instantons are closely tied to one another in the QCD vacuum. Furthermore, the eta-prime meson is closely related to the topology of the QCD vacuum. However, it is difficult to demonstrate the relations among them by perturbative calculations because of the strong interaction in the low-energy region of the QCD. Therefore, we perform simulations of lattice gauge theory and reveal the relations.

In this research, the Pisa group generates gauge field configurations with $N_{f}$ = 2 + 1 dynamical fermions at the physical pion mass under the Pisa-Dubna collaboration. The standard configurations and the configurations to which uniform magnetic fields are applied are prepared at low and finite temperatures. The intensity of the uniform magnetic fields varies from $e|B|$ = 0.7 to 1.1 [GeV$^{2}$]. We calculate the eigenvalues and eigenvectors of the overlap Dirac operator that holds the exact chiral symmetry using these configurations.

First, we compute the monopole density. Second, we compute the topological charges and the number of instantons and anti-instantons and compare the distributions of the eigenvalues of the overlap Dirac operator with the predictions of random matrix theory. Third, we estimate the eta-prime meson mass from the disconnected contribution of the quark bilinear operator for the pseudoscalar density. Finally, we demonstrate the impact of the external magnetic fields on the monopoles, instantons, spectrum of the overlap Dirac operator, and eta-prime meson mass.

In my talk, I will present the preliminary results obtained using the small lattice volumes.

Speaker: Masayasu Hasegawa (JINR, BLTP)

1000-M.Hasegawa_12Oct2022_ver1.pdf

2 Monopole and monopoleless components of the lattice gauge field in the maximal Abelian gauge

The lattice gauge field is decomposed into the monopole and monopoleless components after the Maximal Abelian gauge is fixed. The interaction potential between static charges is calculated for each component and their sum is compared with the full non-Abelian static potential. A good agreement is found in both SU(2) and SU(3) gluodynamics and in two-color QCD. Implications of this result are discussed.

Speaker: Vitaly Bornyakov (IHEP, Protvino)

1020-Conf-SPb-2022.pdf

3 Analytic Properties of the Quark Density in QC$_2$D and the Sign Problem

Analytic dependence of the quark density on the quark chemical potential is extracted from the data simulated in lattice rergularization of QC$_2$D. It is shown that the cluster expansion model provides the best parametrization for analytic continuation of the quark density from imaginary to real values of the chemical potential. The problem of calculation of canonical partition functions and partial probabilities at high quark densities is discussed.

Speaker: Roman Rogalyov (NRC "Kurchatov Insitute" - IHEP)

1040-rogalyov.pdf

4 TBA

5 Casimir effect in 3+1 dimentional lattice Abelian and non-Abelian gauge theories

Compact U(1) gauge theory in 3+1 dimensions possesses the confining phase which is characterized by a linear raise of the potential between particles with opposite electric charges at sufficiently large inter-particle separation. This phenomenоn is closely related to the color confinement in non-Abelian gauge theories such as QCD. In QED the condensation of Abelian monopoles at strong gauge coupling leads to confinement of electric charges because monopole condensate squeezes the electric flux into a thin electric tube which plays the role of confining string. We investigate how the vacuum structure of the theory is influenced by adding ideally conducting parallel plates associated with Casimir effect which predicts that the energy of vacuum fluctuations is modified by the presence of physical bodies. Using first-principal numerical simulations in compact U(1) lattice gauge theory we have found that as the distance between the plates diminishes, the vacuum between the plates undergoes a deconfining transition and the phase transition point shifts towards weaker gauge coupling. The phase diagram in the space of the lattice gauge coupling and the inter-plate distance is obtained. We also discuss our new results on the non-Abelian Casimir effect in SU(3) gauge theory.

Speaker: Aleksei Tanashkin (Pacific Quantum Center, Far Eastern Federal University)

10:00 MQFT Plenary session

11:40 Coffee break

12:00 MQFT Plenary session

13:30 Lunch

15:00 Excursion

Thursday 13 October

10:00 MQFT Plenary session

10:45 Coffee break

LFTQCD Session

6 Various corners of QCD and 2 color QCD phase diagrams

Phase structure of dense quark matter with chiral and isospin imbalance is considered in the framework of effective models. There has been considered as two color as well as three color QCD. It was shown that chiral imbalance has several rather peculiar properties such as being universal catalyzer,
i. e. it catalyzes all the considered symmetry breaking patterns in the system, including the diquark condensation phenomenon (color superconductivity). Duality properties found earlier have been considered in both case.

Speaker: Dr Roman Zhokhov

Pres_Conference_LFT_2022_short (4).pdf

7 Spectral functions of the O(N) model from the functional renormalization group approach

Due to the substantial progress in the development of functional approaches for the computation real-time correlation functions, new prospects have arisen to investigate diverse collective physical phenomena in the systems in a strong coupling regime. At the same time, the main problem with computations directly in Minkowski space is a complex analytical structure of correlation functions.
We will discuss the computation of spectral functions of bound states using the real-time formulation of a functional renormalization group (FRG) approach on the example of the O(4)-symmetric model. The computation is based on the Kallen-Lehmann spectral representation of dressed propagators used in the Wetterich equation -- the flow equation of the effective action. As a first approximation, we solely consider momentum-independent vertices, the so called propagator approximation. Such an approach gives analytic access to the emergent singularities and brunch cuts, which opens the way for the numerical solution of a system of the FRG equations for the spectral functions corresponding to dressed retarded propagators.

Speaker: Nikita Lebedev (N.N. Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research)

11-35-workshop lebedev.pdf

8 Phase diagram of rotating QCD with Nf = 2 clover-improved Wilson fermions

The relativistic rotation causes a change in QCD critical temperature. Various phenomenological and effective models predict a decrease in the critical temperature in rotating QCD. Nevertheless, it follows from lattice simulations that the critical temperature in gluodynamics increases due to rotation. But in QCD the rotation acts on both gluons and fermions, and combination of these effects may lead to unexpected results. In this report the lattice results for a rotating QCD with dynamical Nf=2 clover-improved Wilson quarks will be presented. It is shown that the rotation of gluons and fermions has an opposite effect on the critical temperature. Dependence of the results on the pion mass is also discussed.

Speaker: Dr Artem Roenko (JINR, BLTP)

1155-Roenko_RotationFermionIw_LFTQCD.pdf

9 Influence of relativistic rotation on the equation of state of gluodynamics

Relativistic rotation may have some impact on various properties of quark-gluon plasma. For example, lattice simulations show an increase in critical temperature of both QCD and gluodynamics due to rotation. In this report the first lattice study of an effect that rotation has on gluodynamics’ equation of state will be presented. In particular, it will be shown that rotation’s impact on free energy density changes sign with temperature increase.

Speaker: Dmitrii Sychev (BLTP JINR, MIPT)

10 Electromagnetic conductivity of dense quark-gluon plasma

In this report we present the results on the study of the electromagnetic conductivity in dense quark-gluon
plasma obtained within lattice simulations with Nf=2+1 dynamical quarks. We employ stout improved
rooted staggered quarks at the physical point and the tree-level Symanzik improved gauge action.
The simulations are performed at imaginary baryon chemical potential, and the Tikhonov regularisation
method is used to extract the conductivity from current-current correlators. Our results indicate
an increase of QGP electromagnetic conductivity with real baryon density, and this dependence is quite strong.

Speaker: Prof. Victor Braguta (BLTP JINR)

1235-report.pdf

11:15 MQFT Plenary session

12:55 Lunch

14:30 MQFT Parallel sessions

16:15 Coffee break

16:45 MQFT Parallel sessions

18:30 Conference dinner

Friday 14 October

10:00 MQFT Plenary session

10:45 Coffee break

11:15 MQFT Plenary session

12:45 Lunch

14:30 MQFT Parallel sessions

16:15 Coffee break