The usual Minkowski vacuum in an accelerated frame of reference is known to look like a “thermal bath” of particles. This effect is well known and called the Unruh effect, and is an analog of Hawking radiation in space with zero curvature. Thus, the Minkowski vacuum looks like a heated medium from the point of view of an accelerated observer, and the natural goal is to study the properties of such a medium in more detail. We show that if the Minkwoski vacuum is cooled, and we achieve a temperature below the Unruh temperature, then a phase transition occurs associated with the “fall beyond the horizon” of the lower Matsubara modes. This transition has many remarkable features, for example, for massless particles it is “polynomial,” and is also associated with the breaking of conformal symmetry.

The correlations of the velocities and of the vorticities for pions and nucleons are investigated in frames of the PHSD model for Au+Au collisions at √(s_NN)=7.8 GeV and fixed impact parameter b=7.5 fm. The different behavior of correlations for these kinematic quantities is observed. It is shown that after the time of the separation of the nuclei this difference is due to the ‘microscopic’ Hubble flow. However, for earlier times the reasons are more complicated.

The Spin Physics Detector collaboration proposes to install a universal detector in the second interaction point of the NICA collider under construction (JINR, Dubna) to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to 10^32 cm^-2 s^-1. As the main goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurement of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. This document is dedicated exclusively to technical issues of the SPD setup construction.

We present the results of [1], where good agreement was obtained between calculations within the framework of analytic QCD and experimental data on polarized Bjorken sum rule. The heavy quark contributions are taken into account.

By chiral effects, one understands the manifestations of chiral gauge anomaly and of gravitational chiral anomaly in hydrodynamics. In the last two to three years, our understanding of chiral effects has considerably changed. Here, we present a mini-review of two topics: first, a shift in understanding symmetry, which underlies the chiral magnetic effect and second, the interpretation of the chiral kinematical effect uncovered recently.

The Minkowski vacuum in an accelerated frame behaves like a fluid that has not only a finite temperature due to the Unruh effect, but also a finite shear viscosity. Moreover, the ratio of this viscosity to the entropy density exactly satisfies the Kovtun-Son-Starinets bound, inspired by the string theory eta=s = 1=4 pi. The origin of this viscosity is purely kinematical and is believed to be related to entanglement introduced by the Rindler horizon. We directly calculate the viscosity, entropy density, and their ratio for massless fields with spins 1=2 and 1. We show that locally the ratio of viscosity to entropy density can be below the limiting value 1=4 pi at distances of the order of the thickness of the membrane corresponding to the stretched horizon, and is described by the universal function for different spins. In particular, on the membrane surface eta=s = 1=8 pi.

We present the results of [1], where good agreement was obtained between analytical calculations within the framework of QCD and experimental data on polarized Bjorken sum rule. The photoproduction limit was also considered, and a new representation of the perturbative contribution to the polarized Bjorken sum rule was obtained.

Taking into account the recent parameterizations of parton distribution functions (PDFs), % obtained in the recent time, the momentum transfer dependence of generalized parton distributions (GPDs) of nucleons is obtained in the limit $\xi \rightarrow 0$. The gravitational quark and gluon form factors of nucleons are calculated. It is shown that the gluon gravitational radius of the nucleon is comparable to the electromagnetic radius of the proton. The power dependence of form factors is investigated. As a result, it was obtained that the quark gravitational form factor is reproduced by the dipole form, while the form of the gluon gravitation form factor corresponds to the triple form.

One of the goals of the future Multi-Purpose Detector (MPD) is to investigate vortical structure of matter by studying polarization observables in heavy-ion collisions in the energy range of several GeV per nucleon. We present here the performance study of global polarization of hyperons within the framework of the MPD experiment at Nuclotron-based Ion Collider fAcility (NICA) to analyze the sensitivity of the detector to these observables during the initial stage of the experimental setup. The study has been performed via Monte Carlo simulation made for the collisions of Bi+Bi at √(s_NN) = 9.02 GeV using Parton-Hadron-String Dynamics (PHSD) model. Full chain of spin direction transfer from the model to MC simulation has been implemented.

We consider heavy quark contributions to the polarized Bjorken sum rule. We found good agreement between the experimental data and the predictions of analytic QCD. To satisfy the limit of photoproduction, we use new representation of the perturbative part of the polarized Bjorken sum rule, recently proposed.

Preliminary results on determination of the microscopic Hubble constant for pions and nucleons in Au + Au collisions at √(s_NN) = 7.8 GeV for a range of times and b = 7.5 fm are presented and discussed. The data are simulated within PHSD model. A typically used method based on the fit of the velocity profile is considered in detail. Also a new method for determination of the Hubble parameter is proposed. It consists in the analysis of the statistical distribution of the divergence of the velocity field and getting the Hubble parameter as a position of a particular peak of the distribution. A comparison of the methods is done.

We construct the hydrodynamic expansion for a rotating and accelerated medium in a curved space-time, and establish the relationship between the currents generated by the cosmological constant and the acceleration. Then we consider the more general case with a nonzero Weyl tensor, and show the duality between the current in flat space-time and the gravitational axial anomaly. This generalizes the previous derivation to the case with a nonzero Ricci tensor.

The dependence of the angular distribution of lepton pairs in hadronic collisions on the choice of the reference frame is discussed. A geometric description of the transformations of the angular distribution coefficients is presented. The rotational invariants including all coefficients and restrictions on them are considered. The data of the E615 experiment have been processed and a verification of rotational invariants on their basis has been presented.

We present a QCD-motivated approach to the analysis of polarized Bjorken sum rule in the nonperturbative infrared region Q(2) < 1 GeV2. In this approach, we use the Gerasimov-Drell-Hearn sum rule as a boundary condition and move from the region of large momentum transfers to the low Q(2)-region. We show that the developed approach works well and note a possible problem with the Jefferson Lab data at Q(2) < 0.1 GeV2.

BM@N (Baryonic Matter at Nuclotron) is the first experiment operating and taking data at the Nuclotron/NICA ion-accelerating complex.The aim of the BM@N experiment is to study interactions of relativistic heavy-ion beams with fixed targets. We present a technical description of the BM@N spectrometer including all its subsystems.

In a fluid with vorticity and acceleration, an axial current arises in the third order of gradient expansion, called the kinematical vortical effect (KVE). While existing in the absence of gravitational fields, it is nevertheless associated with effects in curved space-time, namely with the gravitational chiral quantum anomaly. In this paper, the KVE transport coefficients were found using the Zubarev quantum-statistical density operator for the Rarita-Schwinger-Adler theory, which includes fields with spins 3/2 and 1/2. A prediction is made about the possible form of the transport coefficients for massless fields with arbitrary spin.

We consider an accelerated relativistic fluid in four-dimensional (anti-)de Sitter space-time. Analyzing only hydrodynamic equations, we construct the equilibrium stress-energy tensor. We confirm that (A)dS vacuum corresponds to a thermal bath in the accelerated frame with a temperature, depending on the acceleration in a flat higher-dimensional (namely, five-dimensional) space, in which curved space-times are embedded. We develop the duality between hydrodynamics and gravity finding a direct relationship between the transport coefficients in flat and curved space-times.

Classical analogs of chiral vortical and magnetic effects, generated by the currents possessing the hydrodynamical helicity are considered. The earlier found phenomenon of helicity separation in heavy-ion collisions leads to the appearance of currents of opposite signs at the different sides of reaction plane, accompanied by the current parallel to the plane. We discuss briefly relation between classical and quantum chiral effects.

In extensions of the Standard Model (SM) of particle physics a light scalar from a hidden sector can interact with known particles via mixing with the SM Higgs boson. If the scalar mass is of GeV scale, this coupling induces the scalar decay into light hadrons, that saturates the scalar width. Searches for the light scalars are performed in many ongoing experiments and planned for the next generation projects. Applying dispersion relations changes the leading order estimate of the scalar decay rate into pions by a factor of about a hundred indicating the strong final state interaction. This subtlety for about thirty years prevented any reliable inference of the model parameters from experimental data. In this letter we use the gravitational form factor for neutral pion extracted from analysis of $\gamma^*\gamma\to\pi^0\pi^0$ processes to estimate the quark contribution to scalar decay into two pions. We find a factor of two uncertainty in this estimate and argue that the possible gluon contribution is of the same order. The decay rate to pions smoothly matches that to gluons dominating for heavier scalars. With this finding we refine sensitivities of future projects to the scalar-Higgs mixing. The accuracy in the calculations can be further improved by performing similar analysis of $\gamma^*\gamma\to K K$ and $\gamma^*\gamma\to\eta\eta$ processes and possibly decays like $J/\psi\to\gamma+\pi\pi$.