Core-collapse supernovae are the powerful explosions of massive stars that occur at the end of their lives. They play a crucial role in the evolution of the Universe, producing most elements heavier than iron and leading to the formation of neutron stars and black holes. Despite their importance, the details of how they explode are still unclear. In this talk, I will review the recent progress...
One of the challenges in nuclear physics is to describe finite nuclei and neutron stars within the same theoretical framework. A crucial entity is the nuclear Equation of State (EoS), which can be defined in terms of a set of empirical parameters (saturation density, compressibility, symmetry energy and its derivatives etc). In turn, these quantities are constrained using experimental data on...
We give the review of modified gravity as applied to Universe evolution. It is shown that number of modified gravities may provide the consistent unification of the early-time inflation with late-time acceleration. Special attention is paid to F(R) gravity which represents the most developed class of such theories. Specific features of possible evolution in such theories are indicated:...
Knowledge of the equation of state (EoS) of cold and dense baryonic matter is essential to describe the properties of neutron stars (NSs). With an increase of the density new baryon species can appear in NS matter, as well as various meson condensates. In previous works we developed relativistic mean-field (RMF) models with hyperons and $\Delta$-isobars, which passed the majority of known...
In order to prove the existence of a critical end point (CEP) in the QCD phase diagram it is sufficient to demonstrate that at zero temperature $T=0$ a first order phase transition exists as a function of the baryochemical potential $\mu$, since it is established knowledge from ab-initio lattice QCD simulations that at $\mu=0$ the transition on the temperature axis is a crossover.
We present...
We compute the transport coefficients of quark matter in the strong coupling regime within the two-flavor Nambu--Jona-Lasinio model. We apply the Kubo formalism to obtain the thermal ($\kappa$) and the electrical ($\sigma$) conductivities as well as the shear ($\eta$) and the bulk viscosities ($\zeta$) at leading order in the $1/N_c$ power counting scheme. In this approximation the...
As is well known, in quantum field theory (QFT) the quantum vacuum (QV) is
represented as an infinite set of different fluctuating virtual particles
and fields in four-dimensional Minkowski space-time. In this connection, a
natural question arises: what is the structure of QV, when the latter is
in a state of statistical equilibrium and there is no external influence
on it? It is obvious that...
We study the anisotropic self-gravitating objects with polytropic equation of state in both contexts of Newtonian gravity and General Relativity.
First we discuss Newtonian case, where we start with hydrostatic equilibrium equation. By arriving at Lane--Emden equation we study the effects of an anisotropic pressure on the boundary conditions of the anisotropic Lane–Emden equation and the...
Neutrino emission from neutron stars is subject of strong modifications due to collective effects in nuclear matter like the pion polarization effect and the Cooper pairing of nucleons. The larger is the star mass (central density) the stronger is the pion polarization. The ``nuclear medium cooling scenario” relates slow and rapid neutron star cooling to the neutron star masses (interior...
A two-phase description of the quark-nuclear matter hybrid equation of state that takes into account the effect of excluded volume in both the hadronic and the quark-matter phases is introduced. The nuclear phase manifests a reduction of the available volume as density increases, leading to a stiffening of the matter. The quark-matter phase displays a reduction of the effective string-tension...
In this talk I will present a temperature dependent equation of
state (EoS) including the entire baryon octet, being compatible with
the main constraints from nuclear physics and, in particular, with a
maximum mass for cold $\beta$-equilibrated neutron stars of
$2M_\odot$ in agreement with recent observations. As an application,
numerical stationary models for rapidly (rigidly)...
The $f(R)$ gravity represents the simplest purely geometrical generalization of
the Einstein general theory of relativity without undesirable ghosts. The
pioneer $R+R^2$ model of inflation (1980) contains only one adjustable
parameter taken from observations, has a graceful exit from inflation and
a natural mechanism for creation and heating of matter after its end. It
produces a very good fit...
Calculation of symmetry energy using Argonne family potentials
with three nucleon interaction
Z. Asadi and M. Bigdeli
Department of Physics, University of Zanjan, Zanjan, Iran
The symmetry energy has been given attention in recent years because of its fundamental important role in both astrophysics and nuclear physics. The symmetry energy S is the difference of the energy per...
A Low-EneRgy Nuclear Interaction Chamber, LERNIC, has been developed to be used as an active target system for nuclear astrophysics experiments. LERNIC is a position and time sensitive detector system based on the low-pressure MWPC technique. While the astrophysically relevant nuclear reaction processes at stellar burning temperatures are dominated by radiative captures, in this experimental...
We present a new technique for describing geodesic congruences (for example the trajectory of a gas of photons or particles) crossing a generic light-like shell in vacuum. In particular the change in the direction of the vector field of the congruence has been derived and shown to be in agreement with the results of Barrabes and Hogan thus demonstrating the validity of this technique. For the...
Taking into account the neutrino energy losses the time dependences of the luminosities of a white dwarf and four strange dwarfs with masses of $0.5 M_\odot$ (the mass of white dwarf EG 50 with the surface temperature $2.1\cdot 10^4 K$) has been determined. It was assumed that these configurations radiate only at the expense of thermal energy reserves. It has been shown that the sources of...
The abstract: In this talk I give a brief review of our recent development on the cosmological dynamics in the Einstein-Gauss-Bonnet gravity. The special attention is paid to the models which allow realistic compactification. We require only for model to be free of future singularities and has a ``standard'' cosmological singularity af the origin. Using such weak requirements, for the simplest...
In this talk we examine the vacuum fermionic current induced by a magnetic field confined in a cylindrical tube of finite radius a in cosmic string spacetime. Three distinct configurations of magnetic fields are taken into account:
∙ a cylindrical shell of radius a,
∙ a magnetic field proportional to 1/r,
∙ a constant magnetic field.
In these three cases, the axis of the...
Gravitational waves, Electromagnetic radiation and emission of High Energy Particles probe the phase structure of the EoS of dense matter produced at the crossroad of the closely related relativistic collisions of heavy ions and of binary neutron stars.
3+1 dimensional special- and general relativistic hydrodynamic model studies reveal a unique window of opportunity to observe phase...
The unknown nature of dark matter and dark energy, as well as rapid improvements in the accuracy of the astronomical data, inspired studies of extensions of Einstein's theory of General Relativity and ways of testing them against observations. I will review the current state of the very active field of Testing Gravity, and what we can expect to learn about Gravity from the next generation of...
We present the application of our technique to obtain equation of state (EoS) by the Functional Renormalization Group (FRG) method presented earlier. Using the expansion of the effective potential in a base of harmonic functions at finite chemical potential we can provide a general framework for the calculation of the EoS. Within this theoretical framework we determined the equation of state...
We present a systematic analysis of homogeneous and isotropic cosmologies in Horndeski model which is the most general scalar-tensor theory of gravity with second-order field equations.
A special attention is paid to the particular subclass of Horndeski theory, namely, the model with the scalar field $\phi$ possessing the nonminimal kinetic coupling to curvature given as $\eta...
Relativistic mean-field (RMF) models with density dependent (DD) couplings have been used successfully to describe nuclear matter and finite nuclei. They usually assume a dependence of the nucleon-meson couplings on the so-called vector density that is derived from the baryon current. A dependence on other densities, in particular the scalar density, was not really explored although suggested...
We investigate the influence of a cosmic string on the vacuum fluctuations of the electromagnetic field in background of (D+1)-dimensional de Sitter spacetime.
The expectation values (VEVs) of physical characteristics for the Bunch-Davies vacuum state are evaluated. The VEVs are presented in a decomposed form where
the topological parts induced by the cosmic string are explicitly extracted....
Magnetars have been observationally determined to have surface magnetic fields of order of $10^{14} –10^{15}$ G, the implied internal field strength being several orders larger. We discuss the effect of strong field on the dense matter expected to be inside neutron stars. We describe the microphysics, phenomenology, and astrophysical implication of strong field induced unpairing effect that...
The PSR B0833-45 (the Vela pulsar) is the famous neutron star. Its age is about $11$ kyr and it cools mainly via neutrino emission from its superdense core. Its surface temperature of $\sim 0.7$ MK was obtained from the analysis of its X-ray spectrum assuming that the star's mass is $1.4$ $M_\odot$ and the radius is $10$ km (Pavlov et al. 2001, ApJ 552, L129). The Vela pulsar appears to be one...
The dependences of the mass and the mass defect on the baryonic mass of the isothermal (the stars with the same core temperature) and the isentropic (the stars with the same entropies per one baryonic chargе) series of the hot strange stars are investigated .The stability of these stars is determined by these dependences. It is shown that isentropic series of the hot strange stars are also ...
A Bayesian analysis for a new class of realistic models of hybrid equations of state (EoS) with mixed phase is performed. The mixed phase is described by a one parameter simple model. The parameter represents the impact of the mixed phase structure to the pressure. It is demonstrated that the observation of a possible pair of high-mass twin stars would have a sufficient discriminating power to...
For a description of matter at high temperature and density effective
models of Nambu-Jona-Lasinio type have proven most useful. The Polyakov
loop extended NJL (PNJL) model can reproduce results of lattice QCD at
zero and imaginary chemical potential, where LQCD has no sign problem. In
the contribution we present the dependence of the first-order phase
transition line and its critical endpoint...
Pulsar glitches are commonly interpreted as angular momentum transfers occurring between two fluids present in the stellar interior, triggered by the rapid motion of superfluid vortex lines at large scales. We consider for the first time all general relativistic effects in a numerical model for glitches. First, we show numerical calculation of stationary configurations of neutron stars...
The mechanism of magnetic field generation in hybrid neutron stars (consisting of “npe”
hadronic, “2SC” and “CFL” quark phases) is considered. We assume that rotational vortices in “npe”
and “CFL” phases with quantum of circulation 𝜋ℏ/𝑚 are continued in “2SC” phase as well. Since
superconducting matter in “npe” and “2SC” phases is charged, rotation induced entrainment currents
arise around...
We briefly review the properties of static, spherically symmetric configurations of general relativity with a minimally coupled scalar field $\phi$ whose kinetic energy is negative in a restricted (strong-field) region of space and positive outside it [1--3]. This ``trapped ghost'' concept may in principle explain why no ghosts are observed under usual, weak-field conditions. The...
The effect of model parameters of quark matter equation of state on the magnitude of the maximum mass of a hybrid star is investigated. The quark matter is described within the framework of the extended MIT bag model with one-gluon exchange corrections taken into account. For nucleon matter within the density region, corresponding to a phase transition, the relativistic equation of state is...
