scholarly journals Fluctuations and phases in baryonic matter

2021 ◽  
Vol 57 (7) ◽  
Author(s):  
Len Brandes ◽  
Norbert Kaiser ◽  
Wolfram Weise
Keyword(s):  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Test Case ◽  
Baryonic Matter ◽  
Prototype Test ◽  
Group Methods ◽  
Stabilization Effect ◽  
Dynamical Fluctuations

AbstractThe phase structure of baryonic matter is investigated with focus on the role of fluctuations beyond the mean-field approximation. The prototype test case studied is the chiral nucleon-meson model, with added comments on the chiral quark-meson model. Applications to nuclear matter include the liquid-gas phase transition. Extensions to high baryon densities are performed for both nuclear and neutron matter. The role of vacuum fluctuations is systematically explored. It is pointed out that such fluctuations tend to stabilize the hadronic phase characterized by spontaneously broken chiral symmetry, shifting the chiral restoration transition to very high densities. This stabilization effect is shown to be further enhanced by additional dynamical fluctuations treated with functional renormalisation group methods.

THE ROLE OF ANTIKAON CONDENSATES IN THE EQUATION OF STATE OF NEUTRON STARS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1545-1548 ◽  
Author(s):  
F. FERNÁNDEZ ◽  
A. MESQUITA ◽  
M. RAZEIRA ◽  
C. A. Z. VASCONCELLOS
Keyword(s):  
Neutron Stars ◽  
Electric Charge ◽  
Chemical Potential ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Charge Neutrality ◽  
The Mean ◽  
Nucleon Matter

We study the consequences of the presence of a negative electric charge condensate of antikaons in neutron stars using an effective model with derivative couplings. In our formalism, nucleons interact through the exchange of σ, ω and ϱ mesons, in the presence of electrons and muons, to accomplish electric charge neutrality and beta equilibrium. The phase transition to the antikaon 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 antikaon condensate. Assuming neutrino-free matter, we observe a rapid decrease of the electron chemical potential produced by the gradual substitution of electrons by kaons to accomplish electric charge neutrality. The exotic composition of matter in neutron star including antikaon condensation and nucleons can yield a maximum mass of about M ns ~ 1.76 M ⊙.

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.

PROTO-NEUTRON STAR FORMATION WITH DELTA-RESONANCE MATTER AND TRAPPED NEUTRINOS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1541-1544 ◽  
Author(s):  
J. C. T. OLIVEIRA ◽  
A. G. SOUZA ◽  
S. B. DUARTE ◽  
H. RODRIGUES
Keyword(s):  
Neutron Star ◽  
Mean Field ◽  
Field Approximation ◽  
Medium Composition ◽  
Hadronic Matter ◽  
Mean Field Approximation ◽  
Delta Resonance ◽  
Leptonic Sector ◽  
Proto Neutron Star

In the present work we study the equation of state for asymmetric hadronic matter, to be applied in neutron star structure calculation. The delta-rich hadronic stellar matter condensate is studied in the context of mean-field approximation in an extended Walecka's theory version, including the Rarita–Schwinger 3/2-spinor to the hadronic sector. The leptonic sector is also incorporated in beta-equilibrium to the dense stelar medium composition. The role of neutrino trapping for the the formed photo-neutron structure including delta matter in its composition is discussed.

SEXUAL REPRODUCTION IN A SIMPLE GROWTH POPULATION MODEL

2012 ◽  
Vol 23 (05) ◽  
pp. 1250022
Author(s):  
CARLOS GENTIL ORO LEMOS ◽  
MARCIO SANTOS
Keyword(s):  
Sexual Reproduction ◽  
Mean Field ◽  
Field Approximation ◽  
Reaction Model ◽  
Mean Field Approximation ◽  
Spatial Density ◽  
Simple Growth ◽  
Offspring Generation ◽  
Surface Reaction Model

One of the most important characteristics in the survival of a species is related to the kind of reproduction responsible for the offspring generation. However, only in the last years the role played by sexual reproduction has been investigated. Then, for a better understanding of this kind of process we introduce, in this work, a surface reaction model that describes the role of the sexual reproduction. In our model two different elements of the species, representing male and female, can interact to reproduce a new element. The sex of this new element is chosen with a given probability and in order to take into account the mortality rate we introduce another kind of individual. The value of the spatial density of this element remains constant during the time evolution of the system. The model is studied using Monte Carlo simulations and mean field approximation. Depending on the values of the control parameters of the model, the system can attain two stationary states: In one of them the population survives and in the other it can be extinguished. Besides, accordingly to our results, the phase diagram of the model shows a discontinuous transition between these two states.

scholarly journals Statistics effects in extremal black holes ensemble

2019 ◽  
Vol 34 (32) ◽  
pp. 1950215
Author(s):  
A. M. Gavrilik ◽  
A. V. Nazarenko
Keyword(s):  
Black Holes ◽  
Mean Field ◽  
Field Approximation ◽  
Statistical Weight ◽  
Fixed Number ◽  
Mean Field Approximation ◽  
Visible Effect ◽  
Bose Einstein ◽  
Extremal Black Holes

We consider the grand canonical ensemble of the static and extremal black holes, when the equivalence of the electric charge and mass of individual black hole is postulated. Assuming uniform distribution of black holes in space, we are finding the effective mass of test particle and mean time dilation at the admissible points of space, taking into account the gravitational action of surrounding black holes. Having specified the statistics that governs extremal black holes, we study its effect on those quantities. Here, the role of statistics is to assign a statistical weight to the configurations of certain fixed number of black holes. We borrow these weights from Bose–Einstein, Fermi–Dirac, classical and infinite statistics. Using mean field approximation, the aforementioned characteristics are calculated and visualized, which permits us to draw the conclusions on visible effect of each statistics.

scholarly journals Pairing correlations and symmetries in odd-A nuclei.

2018 ◽  
Vol 178 ◽  
pp. 02002 ◽  
Author(s):  
J. Luis Egido ◽  
Marta Borrajo
Keyword(s):  
Angular Momentum ◽  
Particle Number ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Angular Momentum Projection ◽  
Hartree Fock ◽  
Pairing Correlations ◽  
Highly Correlated

The pairing correlations in odd-A nuclei are analyzed in the mean field approximation and beyond. In particular the role of symmetry conservation is investigated. We find that particle number projection after the variation (PN-PAV) has little effect on the pairing correlations specially in the weak pairing regime. This is in contrast to the variation after particle number projection (PN-VAP) approach where a strong effect is found. The situation is specially critical in odd nuclei because the pairing correlations vanish due to the blocking effect and the Hartree-Fock-Bogoliubov wave function collapses to the Hartree-Fock one. The PN-VAP, however, handles perfectly the exact blocking providing highly correlated wave functions. The role of the angular momentum projection is studied only in the PAV approach. We find small changes of the pairing correlation, at least at small angular momentum. In the calculations we use the Gogny interaction well suited to this kind of studies.

scholarly journals Nonlinear optical dynamics of two-dimensional super-lattices of quantum V-emitters

2021 ◽  
Vol 2103 (1) ◽  
pp. 012225
Author(s):  
Davut Ya. Bayramdurdiyev ◽  
Ramil F. Malikov ◽  
Igor V. Ryzhov ◽  
Victor A. Malyshev
Keyword(s):  
Nonlinear Optical ◽  
Mean Field ◽  
Dipole Interaction ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Super Lattice ◽  
The Mean ◽  
The Stability ◽  
Different Response

Abstract We study theoretically the nonlinear optical response of a super-lattice of regularly arranged three-level identical quantum emitters with a doublet in the excited state to the action of a monochromatic electromagnetic field quasi-resonant to optical transitions in the emitter, using into account the dephasing of the system. The total retarded dipole-dipole interaction of the emitters is accounted for in the mean-field approximation. This interaction plays the role of positive feedback, which (in combination with the immanent nonlinearity of emitters themselves) leads to multistability of the super-lattice response. The stability of different response branches is analyzed using the Lyapunov exponents’ method. Another important property of the super-lattice is its high reflectance in a certain frequency range; i.e., within this range, the super-lattice operates as a perfect nanometer mirror; moreover, reflection can be switched to transmission changing slightly the incident field amplitude (bistability). The possibility of the application of the above-mentioned super-lattice optical properties in nanophotonics is discussed.

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