scholarly journals Delta Resonance Coupling with Walecka’s Mesons: Implications to Stellar Matter EoS

2017 ◽  
Vol 45 ◽  
pp. 1760034
Author(s):  
William Silva Gomes ◽  
José Carlos Teixeira de Oliveira ◽  
Hilário Rodrigues ◽  
Sérgio B. Duarte
Keyword(s):  
Phase Transition ◽  
Neutron Star ◽  
Equation Of State ◽  
Mean Field ◽  
Field Approximation ◽  
Coupling Constants ◽  
Mean Field Approximation ◽  
Stellar Matter ◽  
Baryonic Resonance ◽  
Resonance Coupling

In this work we have obtained the equation of state to the highly asymmetric dense stellar matter, using the nonlinear Walecka model in the mean field approximation. We discussed the implication of changes in coupling constant of the delta baryonic resonance on the observable of the neutron star. A detailed analysis of the equation of state and of the baryonic effective mass in respect to changes in the delta coupling constants is carried out. We focus attention on a new aspect observed for pressure when varying the baryonic density of the medium; a first order phase transition like a liquid-gas phase transition was observed for an acceptable range of delta coupled constant values. We have explored the implication of this aspect for the neutron star structure and their maximum masses.

KAON CONDENSATION AND THE NUCLEAR EQUATION OF STATE

2011 ◽  
Vol 20 (supp02) ◽  
pp. 140-145
Author(s):  
ROSANA O. GOMES ◽  
DIMITER HADJIMICHEF ◽  
CÉSAR A. Z. VASCONCELLOS ◽  
ALEXANDRE MESQUITA ◽  
MOISÉS RAZEIRA ◽  
...  
Keyword(s):  
Phase Transition ◽  
Equation Of State ◽  
Degrees Of Freedom ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Charge Neutrality ◽  
Nuclear Equation Of State ◽  
Kaon Condensation ◽  
The Mean

We study the effects of phase transition in the equation of state of a neutron star containing a condensate of anti-kaons, using an effective model with derivative couplings. In our formalism, nucleons interact through the exchange of σ, ω, ϱ, and δ meson fields in the presence of electrons and muons to accomplish electric charge neutrality and beta equilibrium. The phase transition to the anti-kaons condensate was implemented through the Gibbs conditions combined with the mean-field approximation, giving rise to a mixed phase of coexistence between hadron matter and the condensed of anti-kaons. In conclusion, we have found that isovector meson degrees of freedom contribute to tighten the Equation of State of Neutron Stars.

scholarly journals Influence of the equation of state on a compact star made of hidden-sector nucleons

2020 ◽  
Vol 2020 (3) ◽  
Author(s):  
Shinji Maedan
Keyword(s):  
Equation Of State ◽  
Cold Dark Matter ◽  
Compact Star ◽  
Mean Field ◽  
Field Approximation ◽  
Compact Stars ◽  
Mean Field Approximation ◽  
Effective Theory ◽  
Hidden Sector ◽  
Two Parameters

Abstract We study a compact star made of degenerate hidden-sector nucleons which will be a candidate for cold dark matter. A hidden sector like quantum chromodynamics is considered, and as the low-energy effective theory we take the (hidden-sector) $ SU(2) $ chiral sigma model including a hidden-sector vector meson. With the mean field approximation, we find that one can treat the equation of state (EOS) of our model analytically by introducing a variable which depends on the Fermi momentum. The EOS is specified by the two parameters $ C'_{\sigma} $, $ C'_{\omega} $, and we discuss how these parameters affect the mass–radius relation for a compact star as well as the EOS. The dependence of the maximum stable mass of compact stars on the parameter $ C'_{\sigma} $ will also be discussed.

GROSS–WITTEN POINT AND DECONFINEMENT

2005 ◽  
Vol 20 (19) ◽  
pp. 4469-4474 ◽  
Author(s):  
ROBERT D. PISARSKI
Keyword(s):  
Phase Transition ◽  
Gauge Theory ◽  
Critical Point ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
First Order

Following Aharony et al., we analyze the deconfining phase transition in a SU(∞) gauge theory in mean field approximation. The Gross–Witten model emerges as an "ultra"-critical point for deconfinement: while thermodynamically of first order, masses vanish, asymmetrically, at the transition. Potentials for N = 3 are also shown.

scholarly journals Hybrid Stars in the Framework of NJL Models

2017 ◽  
Vol 45 ◽  
pp. 1760026 ◽  
Author(s):  
Gustavo A. Contrera ◽  
Milva Orsaria ◽  
I. F. Ranea-Sandoval ◽  
Fridolin Weber
Keyword(s):  
Phase Transition ◽  
Quark Matter ◽  
Mean Field ◽  
Field Approximation ◽  
Hadronic Matter ◽  
High Mass ◽  
Mean Field Approximation ◽  
Soft Phase ◽  
Non Local ◽  
Hybrid Stars

We compute models for the equation of state (EoS) of the matter in the cores of hybrid stars. Hadronic matter is treated in the non-linear relativistic mean-field approximation, and quark matter is modeled by three-flavor local and non-local Nambu−Jona-Lasinio (NJL) models with repulsive vector interactions. The transition from hadronic to quark matter is constructed by considering either a soft phase transition (Gibbs construction) or a sharp phase transition (Maxwell construction). We find that high-mass neutron stars with masses up to [Formula: see text] may contain a mixed phase with hadrons and quarks in their cores, if global charge conservation is imposed via the Gibbs conditions. However, if the Maxwell conditions is considered, the appearance of a pure quark matter core either destabilizes the star immediately (commonly for non-local NJL models) or leads to a very short hybrid star branch in the mass-radius relation (generally for local NJL models).

STELLAR STRUCTURE FROM QCD

2012 ◽  
Vol 18 ◽  
pp. 91-95
Author(s):  
BRUNO FRANZON ◽  
F. S. NAVARRA ◽  
DAVID FOGAÇA
Keyword(s):  
Equation Of State ◽  
Quark Gluon Plasma ◽  
Mean Field ◽  
Gluon Plasma ◽  
Field Approximation ◽  
Compact Stars ◽  
Stellar Structure ◽  
Mean Field Approximation

Using an equation of state based on a mean-field approximation for QCD (MQCD) to describe the cold quark gluon plasma we study the stellar structure of compact stars.

First Principles Study of the Phase Transitions of MnAs

2006 ◽  
Vol 941 ◽  
Author(s):  
Ivan Rungger ◽  
Stefano Sanvito
Keyword(s):  
Phase Transition ◽  
Curie Temperature ◽  
Cell Volume ◽  
Order Phase Transition ◽  
Structural Changes ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
First Order Phase Transition ◽  
The Stability

ABSTRACTThe magnetic and structural properties of MnAs are investigated by mapping ab initio total energies onto a Heisenberg Hamiltonian. We study the dependence of the Curie temperature over the unit cell volume and an orthorhombic distortion by using the mean field approximation, and find that for orthorhombically distorted cells the Curie temperature is much smaller than for hexagonal cells. We provide an explanation for the structural changes of both the first order phase transition at 318 K and the second order phase transition at 400 K, with the cell volume driving the stability of the different structures in the paramagnetic state. The stable cell is found to be orthorhombic up to a critical lattice constant of about 3.7 Å, above which it remains hexagonal.

QUADRUPOLE DEFORMATION IN NUCLEI AT FINITE TEMPERATURE

1998 ◽  
Vol 13 (33) ◽  
pp. 2705-2713 ◽  
Author(s):  
B. J. COLE ◽  
H. G. MILLER ◽  
R. M. QUICK
Keyword(s):  
Phase Transition ◽  
Finite Temperature ◽  
Mean Field ◽  
Field Approximation ◽  
Quadrupole Deformation ◽  
Mean Field Approximation ◽  
Zero Temperature ◽  
Average Deformation ◽  
The Mean ◽  
Shape Changes

The intrinsic quadrupole deformation has been calculated at finite temperature in 20 Ne both in the mean-field approximation and using an exact shell model diagonalization. The results support the view that the phase transition seen at finite temperature in mean-field calculations is not due to the change in nuclear shape from deformed to spherical, but rather is a collective-to-non-collective transition. Both calculations indicate that the average deformation of 20 Ne changes from β rms ≈0.31 at zero temperature to just over β rms =0.2 at T=3.0 MeV. The calculations also suggest that, in the mean-field approximation, the square of the quadrupole operator, Q[2]·Q[2], is a better indicator of shape changes than Q[2] itself.

THE ROLE OF ANTIKAON CONDENSATES IN THE ISOSPIN ASYMMETRY OF NEUTRON STARS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1553-1556
Author(s):  
A. MESQUITA ◽  
M. RAZEIRA ◽  
C. A. Z. VASCONCELLOS ◽  
F. FERNÁNDEZ
Keyword(s):  
Phase Transition ◽  
Optical Potential ◽  
Mean Field ◽  
Field Approximation ◽  
Mixed Phase ◽  
Hadronic Matter ◽  
Mean Field Approximation ◽  
Isospin Asymmetry ◽  
Nucleon Matter

We study the effects of the scalar-isovector light mesons on the isospin asymmetry and phase transition of hadronic matter to hadronic matter with a condensate of antikaons, using an effective model with derivative couplings. In our formalism, nucleons interact through the exchange of σ, ω, ϱ, δ, and ς mesons in the presence of electrons and muons to accomplish electric charge neutrality and beta equilibrium. The phase transition to the antikaons condensate was implemented through the Gibbs conditions combined with the mean-field approximation, giving rise to a mixed phase of coexistence between nucleon matter and the condensed antikaons. As expected, our results indicate that the scalar-isovector mesons increase the range of the mixed phase–space, they operate for restoring isospin symmetry and they reduce the value of the effective nucleon mass, independently of the depth of the optical potential for antikaons. Also as expected the increase of the depth of optical potential favors the population of antikaons. Our results predict the density threshold of birth of the K-antikaons. The most expressive result of our calculation is the abrupt change in the isospin asymmetry due to the presence of the condensate. Moreover, we have found that scalar-isovector mesons increase the fraction of protons and reduced the fraction of neutrons in the system, since these mesons couple with the conserved isovector current of baryons and thus the minimum in the energy of the system corresponds to saturated isospin states (symmetric in isospin). Finally, we have found as expected that these mesons produce the stiffness of the EoS.

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