arXiv subjects

E. G. Nikonov

Publications and source records attributed to E. G. Nikonov.

At least 19 recordsLinked to original sources

arXiv2021

Induced Surface and Curvature Tensions Equation of State of Hadrons with Relativistic Excluded Volumes and its Relation to Morphological Thermodynamics

An analytical formula that accurately accounts for the Lorentz contraction of the excluded volume of two relativistic hadrons with hard-core repulsion is worked out. Using the obtained expression we heuristically derive the equation of state of Boltzmann particles with relativistic excluded volumes in terms of system pressure and its surface and curvature tension coefficients. The behavior of effective excluded volumes of lightest baryons and mesons is studied at very high temperatures (particle number densities) and for very large values of degeneracy factors. Several parameterizations of the obtained equation of state demonstrate a universal asymptotics of the effective excluded volume at high particle number densities. It is peculiar, that the found maximal packing fraction $η\simeq 0.75$ of Lorentz contracted particles is very close to the dense packing limit of classical hard spheres of same radius $η_{exc} \approx 0.74$. We show that the developed equation of state is the grand canonical formulation of the morphological thermodynamics approach applied to Lorentz contracted rigid spheres.

nucl-th↗

arXiv2020

Second virial coefficients of light nuclear clusters and their chemical freeze-out in nuclear collisions

Here we develop a new strategy to analyze the chemical freeze-out of light (anti)nuclei produced in high energy collisions of heavy atomic nuclei within an advanced version of the hadron resonance gas model. It is based on two different, but complementary approaches to model the hard-core repulsion between the light nuclei and hadrons. The first approach is based on an approximate treatment of the equivalent hard-core radius of a roomy nuclear cluster and pions, while the second approach is rigorously derived here using a self-consistent treatment of classical excluded volumes of light (anti)nuclei and hadrons. By construction, in a hadronic medium dominated by pions, both approaches should give the same results. Employing this strategy to the analysis of hadronic and light (anti)nuclei multiplicities measured by ALICE at $\sqrt{s_{NN}} =2.76$ TeV and by STAR at $\sqrt{s_{NN}} =200$ GeV, we got rid of the existing ambiguity in the description of light (anti)nuclei data and determined the chemical freeze-out parameters of nuclei with high accuracy and confidence. At ALICE energy the nuclei are frozen prior to the hadrons at the temperature $T = 175.1^{+2.3}_{-3.9}$ MeV, while at STAR energy there is a single freeze-out of hadrons and nuclei at the temperature $T = 167.2 \pm 3.9$ MeV. We argue that the found chemical freeze-out volumes of nuclei can be considered as the volumes of quark-gluon bags that produce the nuclei at the moment of hadronization.

nucl-th↗

arXiv2020

Classical excluded volumes of loosely bound light (anti)nuclei and their chemical freeze-out in heavy ion collisions

From the analysis of light (anti)nuclei multiplicities that were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy $\sqrt{s_{NN}} =2.76$ TeV there arose a highly non-trivial question about the excluded volume of composite particles. Surprisingly, the hadron resonance gas model (HRGM) is able to perfectly describe the light (anti)nuclei multiplicities under various assumptions. Thus, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. It is clear, however, that such assumptions are unphysical. Hence we obtain a formula for the classical excluded volume of loosely bound light nuclei consisting of A baryons. To implement a new formula into the HRGM we have to modify the induced surface tension concept to treat the hadrons and (anti)nuclei on the same footing. We perform a simultaneous analysis of hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The HRGM with the induced surface tension allows us to verify different assumptions on the values of hard-core radii and different scenarios of chemical freeze-out of light (anti)nuclei. It is shown that the unprecedentedly high quality of fit $χ^2_{tot}/dof \simeq 0.769$ is achieved, if the chemical freeze-out temperature of hadrons is about $T_h=150$ MeV, while the one for all (anti)nuclei is $T_A=174-175.2$ MeV.

hep-ph↗

arXiv2020

Chemical freeze-out of light nuclei in high energy nuclear collisions and resolution of the hyper-triton chemical freeze-out puzzle

We present a summary of the recent results obtained with the novel hadron resonance gas model with the multicomponent hard-core repulsion which is extended to describe the mixtures of hadrons and light (anti-, hyper-)nuclei. A very accurate description is obtained for the hadronic and the light nuclei data measured by STAR at the collision energy $\sqrt{s_{NN}} =200$ GeV and by ALICE at $\sqrt{s_{NN}} =2.76$ TeV. The most striking result discussed here is that for the most probable chemical freeze-out scenario for the STAR energy the found parameters allow us to reproduce the values of the experimental ratios $S_3$ and $\overline{S}_3$ without fitting.

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arXiv2018

Molecular dynamic simulation of wet water vapour transport in porous medium

Studies of the transport of wet water vapour are relevant for various areas of human activity, including the construction and production of building materials, mining, agriculture, environmental safety of technological processes, scientific research. In particular, one of the methods for extracting highly viscous bitumen grades of oil from the subterranean depths is based on the dilution of the contents of the porous medium by means of pumping coolants. The simplest and environmentally friendly coolant is wet steam containing small drops of water. In addition, with the help of heated water vapour, the filtering elements of collectors are cleaned from sediments of the solid phase (for example, paraffins, gas hydrates and ice floes) on the walls of the porous medium. For realistic modeling of the processes of filtration and heat and mass transfer during the injection of wet steam into a porous medium, it is necessary to investigate the characteristics of the interaction of saturated water vapour with individual through-type pores. In this paper, a study was carried out through mathematical modelling of the dependence of the diffusion rate of wet water vapour on the pressure difference outside the pore that occurs when water vapour is injected into a porous medium. The dependencies of the diffusion rate on the pore cross section, the magnitude of vapour adsorption on the pore walls, as well as the effect of water vapour temperature on all these processes were also investigated. Practical interest is the study of the influence of the rate of cooling of water vapour on the diffusion rate and the adsorption of water vapour on the wall of the pores. The calculations were carried out using a hybrid type model that combines molecular dynamics and macro-diffusion approaches to describe the interaction of water vapour with individual pores.

cond-mat.soft↗

arXiv2018

Molecular dynamic simulation of water vapor interaction with various types of pores using hybrid computing structures

Theoretical and experimental investigations of water vapor interaction with porous materials are very needful for various fields of science and technology. Not only studies of the interaction of water vapor and porous material as a continuous medium, but also the study of the interaction of water vapor with individual pore is very important in these researches. Mathematical modelling occupies an important place in these investigations. In this work, a study of efficiency of various implementations algorithms for MD simulation of water vapor interaction with individual pore is carried out. A great disadvantage of MD is its requirement of a relatively large computational effort and long time in simulations. These problems can be drastically reduced by parallel calculations. In this work we investigate dependence of time required for simulations on different parameters, like number of particles in the system, shape of pores, and so on. The results of parallel calculations are compared with the results obtained by serial calculations.

physics.comp-ph↗

arXiv2018

On separate chemical freeze-outs of hadrons and light (anti)nuclei in high energy nuclear collisions

The multiplicities of light (anti)nuclei were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy $\sqrt{s_{NN}} =2.76$ TeV. Surprisingly, the hadron resonance gas model is able to perfectly describe their multiplicities under various assumptions. For instance, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. In this paper we assume the hard-core radius of nuclei consisting of $A$ baryons or antibaryons to follow the simple law $R(A) = R_b (A)^\frac{1}{3}$, where $R_b$ is the hard-core radius of nucleon. To implement such a relation into the hadron resonance gas model we employ the induced surface tension concept and analyze the hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The hadron resonance gas model with the induced surface tension allows us to verify different scenarios of chemical freeze-out of (anti)nuclei. It is shown that the most successful description of hadrons can be achieved at the chemical freeze-out temperature $T_h=150$ MeV, while the one for all (anti)nuclei is $T_A=168.5$ MeV. Possible explanations of this high temperature of (anti)nuclei chemical freeze-out are discussed.

hep-ph↗

arXiv2018

Possible signals of two QCD phase transitions at NICA-FAIR energies

The chemical freeze-out irregularities found with the most advanced hadron resonance gas model and possible signals of two QCD phase transitions are discussed. We found that the center-of-mass collision energy range of tricritical endpoint of QCD phase diagram is [9; 9.2] GeV which is consistent both with QCD inspired exactly solvable model and with experimental findings.

nucl-th↗

arXiv2018

Equation of State of Quantum Gases Beyond the Van der Waals Approximation

A recently suggested equation of state with the induced surface tension is generalized to the case of quantum gases with mean-field interaction. The self-consistency conditions of such a model and the necessary one to obey the Third Law of thermodynamics are found. The quantum virial expansion of the Van der Waals models of such a type is analyzed and its virial coefficients are given. In contrast to traditional beliefs, it is shown that an inclusion of the third and higher virial coefficients of the gas of hard spheres into the interaction pressure of the Van der Waals models either breaks down the Third Law of thermodynamics or does not allow one to go beyond the Van der Waals approximation at low temperatures. It is demonstrated that the generalized equation of state with the induced surface tension allows one to avoid such problems and to safely go beyond the Van der Waals approximation. Besides, the effective virial expansion for quantum version of the induced surface tension equation of state is established and all corresponding virial coefficients are found exactly.The explicit expressions for the true quantum virial coefficients of an arbitrary order of this equation of state are given in the low density approximation. A few basic constraints on such models which are necessary to describe the nuclear and hadronic matter properties are discussed.

nucl-th↗

arXiv2018

Hard-core Radius of Nucleons within the Induced Surface Tension Approach

In this work we discuss a novel approach to model the hadronic and nuclear matter equations of state using the induced surface tension concept. Since the obtained equations of state, classical and quantum, are among the most successful ones in describing the properties of low density phases of strongly interacting matter, they set strong restrictions on the possible value of the hard-core radius of nucleons. Therefore, we perform a detailed analysis of its value which follows from hadronic and nuclear matter properties and find the most trustworthy range of its values: the hard-core radius of nucleons is 0.30--0.36 fm. A comparison with the phenomenology of neutron stars implies that the hard-core radius of nucleons has to be temperature and density dependent.

hep-ph↗

arXiv2018

Molecular-dynamic simulation of water vapor interaction with suffering pores of the cylindrical type

Theoretical and experimental investigations of water vapor interaction with porous materials are carried out both at the macro level and at the micro level. At the macro level, the influence of the arrangement structure of individual pores on the processes of water vapor interaction with porous material as a continuous medium is studied. At the micro level, it is very interesting to investigate the dependence of the characteristics of the water vapor interaction with porous media on the geometry and dimensions of the individual pore. In this paper, a study was carried out by means of mathematical modelling of the processes of water vapor interaction with suffering pore of the cylindrical type. The calculations were performed using a model of a hybrid type combining a molecular-dynamic and a macro-diffusion approach for describing water vapor interaction with an individual pore. The processes of evolution to the state of thermodynamic equilibrium of macroscopic characteristics of the system such as temperature, density, and pressure, depending on external conditions with respect to pore, were explored. The dependence of the evolution parameters on the distribution of the diffusion coefficient in the pore, obtained as a result of molecular dynamics modelling, is examined. The relevance of these studies is due to the fact that all methods and programs used for the modelling of the moisture and heat conductivity are based on the use of transport equations in a porous material as a continuous medium with known values of the transport coefficients, which are usually obtained experimentally.

physics.flu-dyn↗

arXiv2018

Probing the tricritical endpoint of QCD phase diagram at NICA-FAIR energies

In this contributions we discuss the novel version of hadron resonance gas model which is based on the induced surface tension concept. Also we present new arguments in favor of a hypothesis that the chiral symmetry restoration transition in central nuclear collisions may occur at the center of mass energies 4.3-4.9 GeV and that the deconfinement phase transition may occur at the center of mass energies 8.8-9.2 GeV. These arguments are based on the unique thermostatic properties of the mixed phase and the ones of an exponential mass spectrum of hadrons.

nucl-th↗

arXiv2018

Threshold Collision Energy of the QCD Phase Diagram Tricritical Endpoint

Using the most advanced formulation of the hadron resonance gas model we analyze the two sets of irregularities found at chemical freeze-out of central nuclear-nuclear collisions at the center of mass energies 3.8-4.9 GeV and 7.6-9.2 GeV. In addition to previously reported irregularities at the collision energies 4.9 GeV and 9.2 GeV we found sharp peaks of baryonic charge density. Also we analyze the collision energy dependence of the modified Wroblewski factor and the strangeness suppression factor. Based on the thermostatic properties of the mixed phase of a 1-st order phase transition and the ones of the Hagedorn mass spectrum we explain, respectively, the reason of observed chemical equilibration of strangeness at the collision energy 4.9 GeV and above 8.7 GeV. It is argued that the both sets of irregularities possibly evidence for two phase transitions, namely, the 1-st order transition at lower energy range and the 2-nd order transition at higher one. In combination with a recent analysis of the light nuclei number fluctuations we conclude that the center of mass collision energy range 8.8-9.2 GeV may be in the nearest vicinity of the QCD tricritical endpoint. The properties of the phase existing between two phase transitions are revealed and discussed.

hep-ph↗

arXiv2017

Evidence of the QCD tricritical endpoint existence at NICA-FAIR energies

We present a summary of possible signals of the chiral symmetry restoration and deconfinement phase transitions which may be, respectively, probed at the center of mass collision energies at 4.3-4.9 GeV and above 8.7-9.2 GeV. It is argued that these signals may evidence for an existence of the tricritical endpoint of QCD phase diagram at the collision energy around 8.7-9.2 GeV. The equation of state of hadronic matter with the restored chiral symmetry is discussed and the number of bosonic and fermionic degrees of freedom is found.

nucl-th↗

arXiv2017

2D microscopic and macroscopic simulation of water and porous material interaction

In various areas of science, technology, environment protection, construction, it is very important to study processes of porous materials interaction with different substances in different aggregation states. From the point of view of ecology and environmental protection it is particularly actual to investigate processes of porous materials interaction with water in liquid and gaseous phases. Since one mole of water contains $6,022140857\cdot 10^{23}$ molecules of $\mathtt{H_2O}$, macroscopic approaches considering the water vapor as continuum media in the framework of classical aerodynamics are mainly used to describe properties, for example properties of water vapor in the pore. In this paper we construct and use for simulation the macroscopic two-dimensional diffusion model describing the behavior of water vapor inside the isolated pore. Together with the macroscopic model it is proposed microscopic model of the behavior of water vapor inside the isolated pores. This microscopic model is built within the molecular dynamics approach. In the microscopic model a description of each water molecule motion is based on Newton classical mechanics considering interactions with other molecules and pore walls. Time evolution of water vapor - pore system is explored. Depending on the external to the pore conditions the system evolves to various states of equilibrium, characterized by different values of the macroscopic characteristics such as temperature, density, pressure. Comparisons of results of molecular dynamic simulations with the results of calculations based on the macroscopic diffusion model and experimental data allow to conclude that the combination of macroscopic and microscopic approach could produce more adequate and more accurate description of processes of water vapor interaction with porous materials.

physics.flu-dyn↗

arXiv2017

Hadron Resonance Gas Model with Induced Surface Tension

Here we present a physically transparent generalization of the multicomponent Van der Waals equation of state in the grand canonical ensemble. For the one-component case the third and fourth virial coefficients are calculated analytically. It is shown that an adjustment of a single model parameter allows us to reproduce the third and fourth virial coefficients of the gas of hard spheres with small deviations from their exact values. A thorough comparison of the compressibility factor and speed of sound of the developed model with the one and two component Carnahan-Starling equation of state is made. It is shown that the model with the induced surface tension is able to reproduce the results of the Carnahan-Starling equation of state up to the packing fractions 0.2-0.22 at which the usual Van der Waals equation of state is inapplicable. At higher packing fractions the developed equation of state is softer than the gas of hard spheres and, hence, it breaks causality in the domain where the hadronic description is expected to be inapplicable. Using this equation of state we develop an entirely new hadron resonance gas model and apply it to a description of the hadron yield ratios measured at AGS, SPS, RHIC and ALICE energies of nuclear collisions. The achieved quality of the fit per degree of freedom is about 1.08. We confirm that the strangeness enhancement factor has a peak at low AGS energies, while at and above the highest SPS energy of collisions the chemical equilibrium of strangeness is observed. We argue that the chemical equilibrium of strangeness, i.e. $γ_s \simeq 1$, observed above the center of mass collision energy 4.3 GeV may be related to the hadronization of quark gluon bags which have the Hagedorn mass spectrum, and, hence, it may be a new signal for the onset of deconfinement.

hep-ph↗

arXiv2017

Physical properties of Polyakov loop geometrical clusters in SU(2) gluodynamics

We apply the liquid droplet model to describe the clustering phenomenon in SU(2) gluodynamics, especially, in the vicinity of the deconfinement phase transition. In particular, we analyze the size distributions of clusters formed by the Polyakov loops of the same sign. Within such an approach this phase transition can be considered as the transition between two types of liquids where one of the liquids (the largest droplet of a certain Polyakov loop sign) experiences a condensation, while the other one (the next to largest droplet of opposite Polyakov loop sign) evaporates. The clusters of smaller sizes form two accompanying gases, and their size distributions are described by the liquid droplet parameterization. By fitting the lattice data we have extracted the value of Fisher exponent $τ=$ 1.806 $\pm$ 0.008. Also we found that the temperature dependences of the surface tension of both gaseous clusters are entirely different below and above the phase transition and, hence, they can serve as an order parameter. The critical exponents of the surface tension coefficient in the vicinity of the phase transition are found. Our analysis shows that the temperature dependence of the surface tension coefficient above the critical temperature has a $T^2$ behavior in one gas of clusters and $T^4$ in the other one.

hep-lat↗

arXiv2016

Hadron Resonance Gas Model for An Arbitrarily Large Number of Different Hard-Core Radii

We develop a novel formulation of the hadron-resonance gas model which, besides a hard-core repulsion, explicitly accounts for the surface tension induced by the interaction between the particles. Such an equation of state allows us to go beyond the Van der Waals approximation for any number of different hard-core radii. A comparison with the Carnahan-Starling equation of state shows that the new model is valid for packing fractions 0.2-0.22, while the usual Van der Waals model is inapplicable at packing fractions above 0.1-0.11. Moreover, it is shown that the equation of state with induced surface tension is softer than the one of hard spheres and remains causal at higher particle densities. The great advantage of our model is that there are only two equations to be solved and it does not depend on the various values of the hard-core radii used for different hadronic resonances. Using this novel equation of state we obtain a high-quality fit of the ALICE hadron multiplicities measured at center-of-mass energies of 2.76 TeV per nucleon. Furthermore, using the traditional hadron-resonance gas model with multi-component hard-core repulsion and the novel one we investigate the recently suggested model in which the proper volume of a hadron is proportional to its mass. We find that the high-temperature maximum of $χ^2/ndf$ observed in the latter model always appears in the region located far above the limit of its applicability.

nucl-th↗