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Register a new userHybrid stars with the color dielectric and the MIT bag models
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We study the hadron-quark phase transition in the interior of neutron stars (NS). For the hadronic sector, we use a microscopic equation of state (EOS) involving nucleons and hyperons derived within the Brueckner-Bethe-Goldstone many-body theory, with realistic two-body and three-body forces. For the description of quark matter, we employ both the MIT bag model with a density dependent bag constant, and the color dielectric model. We calculate the structure of NS interiors with the EOS comprising both phases, and we find that the NS maximum masses are never larger than 1.7 solar masses, no matter the model chosen for describing the pure quark phase.
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We study the star matter properties for Hybrid equation of state (EoS) by varying the bag constant. We use the Effective-Field-Theory motivated Relativistic Mean-Field model (E-RMF) for hadron phase with recently reported FSUGarnet, G3 and IOPB-I parameter sets. The result of NL3 and NL3${omega rho}$ sets are also shown for comparison. The simple MIT Bag model is applied for the quark phase to construct the hybrid EoS. The hybrid neutron star mass and radius are calculated by varying with $B^{1/4}$ to constrain the $B^{1/4}$ values. It is found that $B^{1/4}$=130-160 MeV is suitable for explaining the quark matter in neutron stars.
We study spectral properties of Dirac operators on bounded domains $Omega subset mathbb{R}^3$ with boundary conditions of electrostatic and Lorentz scalar type and which depend on a parameter $tauinmathbb{R}$; the case $tau = 0$ corresponds to the MIT bag model. We show that the eigenvalues are parametrized as increasing functions of $tau$, and we exploit this monotonicity to study the limits as $tau to pm infty$. We prove that if $Omega$ is not a ball then the first positive eigenvalue is greater than the one of a ball with the same volume for all $tau$ large enough. Moreover, we show that the first positive eigenvalue converges to the mass of the particle as $tau downarrow -infty$, and we also analyze its first order asymptotics.
The Dirac operator, acting in three dimensions, is considered. Assuming that a large mass $m>0$ lies outside a smooth and bounded open set $OmegasubsetR^3$, it is proved that its spectrum is approximated by the one of the Dirac operator on $Omega$ with the MIT bag boundary condition. The approximation, which is developed up to and error of order $o(1/sqrt m)$, is carried out by introducing tubular coordinates in a neighborhood of $partialOmega$ and analyzing the corresponding one dimensional optimization problems in the normal direction.
We formulate a simple model for a gas of extended hadrons at zero chemical potential by taking inspiration from the compressible bag model. We show that a crossover transition qualitatively similar to lattice QCD can be reproduced by such a system by including some appropriate additional dynamics. Under certain conditions, at high temperature, the system consist of a finite number of infinitely extended bags, which occupy the entire space. In this situation the system behaves as an ideal gas of quarks and gluons.
The effect of pasta phases on the quark-hadron phase transition is investigated for a set of relativistic mean-field equations of state for both hadron and quark matter. The results of the full numerical solution with pasta phases are compared with those of an interpolating construction used in previous works, for which we demonstrate an adequate description of the numerical results. A one-to-one mapping of the free parameter of the construction to the physical surface tension of the quark-hadron interface is obtained for which a fit formula is given. For each pair of quark and hadron matter models the critical value of the surface tension is determined, above which the phase transition becomes close to the Maxwell construction. This result agrees well with earlier theoretical estimates. The study is extended to neutron star matter in beta equilibrium with electrons and muons and is applied to investigate the effect of pasta phases on the structure of hybrid compact stars and the robustness of a possible third family solution.
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