共查询到20条相似文献,搜索用时 140 毫秒
1.
R. Costa A.J. Santiago H. Rodrigues J. Sa Borges 《理论物理通讯》2006,46(6):1052-1058
Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy al and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility Ko much higher than expected. For most parameter sets there exists a critical point (pc, δc), where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M⊙, which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass (1.2M⊙) is obtained for r ≌ 0.9 fro. 相似文献
2.
C. Y. Ryu C. H. Hyun S. W. Hong B. K. Jennings 《The European Physical Journal A - Hadrons and Nuclei》2005,24(1):149-157
We investigate the properties of the neutron star with relativistic mean-field models. We incorporate in the quantum hadrodynamics and in the quark-meson coupling models a possible reduction of meson masses in nuclear matter. The equation of state for neutron star matter is obtained and is employed in Oppenheimer-Volkov equation to extract the maximum mass of the stable neutron star. We find that the equation of state, the composition and the properties of the neutron stars are sensitive to the values of the meson masses in medium. 相似文献
3.
We examine the effect of adding mesons f0(975) and $\phi(1020)$
as well as the variety of $U_\Xi^{(N)}$ (the potential well depth
of $\Xi$ in nuclear matter) from -10 MeV to -28 MeV on the
extent of the particles participation and the properties of the
neutron star in the relativistic mean field model. We find that
considering the contribution of f0 and $\phi$ mesons, the
equation of state of the neutron star turns soft, the maximum
mass reduces while the corresponding radius increases. $\Xi^-$
hyperons appear at lower density as $U_\Xi^{(N)}$ becomes deeper, and the
variety of $U_\Xi^{(N)}$ has little effect on the equation of
state and the properties of the neutron star. 相似文献
4.
Using the RMF theory to describe the neutron liquid region in the neutron star and the Fermi gas model or FMT, BPS,and BBP model to describe the crust of the neutron star (referred as Fermi gas+RMF and RMF* respectively),the properties of the neutron star are calculated and compared with those from the RMF theory. Although the EOS at low density has negligible influence on the maximum mass of the neutron star, and its corresponding central density, energy density, and pressure, it changes the mass-radius relationship of neutron stars considerably. The differences of the neutron star radius corresponding to maximum mass between the RMF theory and RMF* calculations are 0.23-0.33 km. 相似文献
5.
N. K. Glendenning 《Zeitschrift für Physik A Hadrons and Nuclei》1987,326(1):57-64
Generalized beta equilibrium involving nucleons, hyperons and isobars is examined for neutron star matter. The hyperons produce a considerable softening of the equation of state. It is shown that the observed masses of neutron stars can be used to settle a recent controversy concerning the nuclear compressibility. Compressibilities less than 200 MeV are incompatible with observed masses. 相似文献
6.
In the framework of the relativistic mean field theory, we investigate K^0 condensation along with K^- condensation in neutron star matter including the baryon octet. The results show that both K^0 and K^- condensations can occur well in the core of the maximum mass stars for relatively shallow optical potentials of K^- in the range of-100 MeV~ -160 MeV. With the increasing optical potential of K^-, the critical densities of K^- decrease and the species of baryons appearing in neutron stars become fewer. The main role of K^0 condensation is to make the abundances of particles become identical leading to isospin saturated symmetric matter including antikaons, nucleons and hyperons. K^- condensation is chiefly responsible for the softening of the corresponding equation of state, which leads to a large reduction in the maximum masses of neutron stars. In the core of massive neutron stars, neutron star matter including rich particle species, such as antikaons, nucleons and hyperons, may exist. 相似文献
7.
K- condensation and quark deconfinement phase transitions in neutron stars are investigated. We use the modified quark-meson coupling model for hadronic phase and the MIT
bag model for quark phase. With the equation of state (EOS) solved
self-consistently, we discuss the properties of neutron stars. We
find that the EOS of pure hadron matter with condensed K- phase
should be ruled out by the redshift for star EXO0748-676, while EOS
containing unpaired quark matter phase with B1/4 being about
180 MeV could be consistent with both this observation and the best
measured mass of star PSR 1913+16. But if the recent inferred massive star among Terzan 5 with
M>1.68M๏ is confirmed,
all the present EOSes with condensed phase and deconfined phase
would be ruled out. 相似文献
8.
We demonstrate that the largest measured mass of a neutron star establishes an upper bound to the energy density of observable cold baryonic matter. An equation of state-independent expression satisfied by both normal neutron stars and self-bound quark matter stars is derived for the largest energy density of matter inside stars as a function of their masses. The largest observed mass sets the lowest upper limit to the density. Implications from existing and future neutron star mass measurements are discussed. 相似文献
9.
10.
11.
How long do neutron star mountains last? The durability of elastically deformed crust is important for neutron star physics including pulsar glitches, emission of gravitational waves from static mountains, and flares from star quakes. The durability is defined by the strength properties of the Yukawa crystals of ions, which make up the crust. In this paper we extend our previous results [Mon. Not. R. Astron. Soc. 407 , L54 (2010)] and accurately describe the dependence of the durability on crust composition (which can be reduced to the dependence on the screening length λ of the Yukawa potential). We perform several molecular dynamics simulations of crust breaking and describe their results with a phenomenological model based on the kinetic theory of strength. We provide an analytical expression for the durability of neutron star crust matter for different densities, temperatures, stresses, and compositions. This expression can also be applied to estimate durability of Yukawa crystals in other systems, such as dusty plasmas in the laboratory (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
D. N. Aguilera 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):828-830
We present results for the spin-1 color-spin-locking (CSL) phase using a NJL-type model in two-flavor quark matter for compact
stars applications. The CSL condensate is flavor symmetric and therefore charge and color neutrality can easily be satisfied.
We find small energy gaps ≃ 1MeV, which make the CSL matter composition and the EoS not very different from the normal quark
matter phase. We keep finite quark masses in our calculations and obtain no gapless modes that could have strong consequences
in the late cooling of neutron stars. Finally, we show that the region of the phase diagram relevant for neutron star cores,
when asymmetric flavor pairing is suppressed, could be covered by the CSL phase. 相似文献
13.
Norman K. Glendenning 《Nuclear Physics A》1988,480(3-4):597-614
Vacuum renormalization corrections are calculated for normal nuclear matter and neutron star matter in the chiral-sigma model. The theory is generalized to include hyperons in equilibrium with nucleons and leptons. The equations of state corresponding to two compression moduli, a “stiff” and “soft” one for nuclear matter, are studied. It is shown that fully one half the mass of a neutron star at the limiting mass is composed of matter at less than twice nuclear density. Neutron star masses are therefore moderately sensitive to the properties of matter near saturation and to the domain of the hyperons, but dominated by neither. The predictions for the two equations of state are compared with observed neutron star masses, and only the stiffer is compatible. 相似文献
14.
15.
In the framework of relativistic mean field theory, the condensations of K- and \bar{K}0 in neutron star matter including baryon octet and Δ quartet are studied. We find that in this case K- and \bar{K}0 condensations canoccur at relative shallow optical potential depth of \bar{K} from -80 MeV to -160 MeV. Both K- and \bar{K}0 condensations favor the appearances of Δ resonances. With \bar{K} condensations all the Δ quartet can appear well inside the maximum mass stars. The appearances of Δ resonances change the composition and distribution of particles at high densities. The populations ofΔ resonances can enhance K- condensation. It is found that in the core of massive neutron stars, neutron star matter includes rich particle species, such as antikaons, baryon octet, and Δ quartet. In the presence of Δ resonances and \bar{K} condensation, the EOS becomes softer and results in smaller maximum mass stars. Furthermore the impact of antikaon condensations,hyperons, and Δ resonances on direct Urca process with nucleons is also discussed briefly. 相似文献
16.
J. F. Gu H. Guo X. G. Li Y. X. Liu F. R. Xu 《The European Physical Journal A - Hadrons and Nuclei》2006,30(2):455-460
Deconfinement phase transition and condensation of Goldstone bosons in neutron star matter are investigated in a chiral hadronic
model (also referred as to the FST model) for the hadronic phase (HP) and in the color-flavor-locked (CFL) quark model for
the deconfined quark phase. It is shown that the hadronic-CFL mixed phase (MP) exists in the center of neutron stars with
a small bag constant, while the CFL quark matter cannot appear in neutron stars when a large bag constant is taken. Color
superconductivity softens the equation of state (EOS) and decreases the maximum mass of neutron stars compared with the unpaired
quark matter. The K0 condensation in the CFL phase has no remarkable contribution to the EOS and properties of neutron star matter. The EOS and
the properties of neutron star matter are sensitive to the bag constant B, the strange quark mass ms and the color superconducting gap Δ. Increasing B and ms or decreasing Δ can stiffen the EOS which results in the larger maximum masses of neutron stars. 相似文献
17.
在过去的十余年中,对非对称核物质的对称能的研究无论从实验还是理论上都取得了较大的突破,这对中子结构及其物态方程的理解具有十分重要的意义。本研究将采用一个相对保守的对称能斜率范围(25 Me VL105Me V)来研究其对快速转动中子星性质的约束,这些性质包括:质量-半径关系、转动惯量、引力红移以及转动形变等。通过该对称能斜率的约束,发现典型中子星(M=1.4M⊙)的半径约束在10.28~13.43 km范围内,这与最近的相关观测相一致。如果观察发现了质量较小的毫秒脉冲星,则将为核物质的对称能较软提供有效的证据。另外还发现,对角动量的一致性可为快转中子星转动惯量的上限提供约束。最后,根据具有低质量伴星的双星EXO0748-676的红移观测,给出了该脉冲星的质量下限(1.5M⊙)。 相似文献
18.
There are over 100 accreting neutron stars in our galaxy, in which matter (typically H/He) is tidally transferred from a secondary companion to the neutron star. Accretion of this matter perturbs the thermal structure of the interior away from that of an isolated cooling neutron star. In this paper. we review how this accretion induces reactions in the crust of the neutron star that keep the interior hot. If the accretion is intermittent, then the heated surface layers are directly observable when accretion stops. This heating also affects the unstable ignition of light elements in the neutron star envelope. Observations of the neutron star cooling following an accretion outburst can in principle constrain the thermal properties of the crust and core. 相似文献
19.
BAO Tmurbagan LI Gen-Quan WANG Zong-Chang YANG Xing-Qiang LIU Guang-Zhou 《中国物理C(英文版)》2011,35(6):539-542
Influences of the bag constant on the properties of hybrid stars are investigated by using relativistic mean field theory and the MIT bag model to describe the hadron phase and quark phase in the interior of neutron stars, respectively. Our results indicate that the onset of hadron-quark phase transition is put off and the appearance of hyperon species is increased with the increase in bag constant. As a result, the hybrid star equation of state for a mixed phase range stiffens whereas that of the quark phase range softens, and the gravitational mass as well as the corresponding radius of hybrid stars are increased obviously. The gravitational mass of a hybrid star is increased from 1.42 Mo (M<,⊙> is solar mass) to 1.63M<,⊙> and the corresponding radius is changed from 9.1 km to 12.2 km when the bag constant (B<'1/4>) is increased from 170 MeV to 200 MeV. It is interesting to find that hybrid star equations of state become non-smooth when the TM2 parameter sets in the framework of relativistic mean field theory used to describe the hadronic matter, and consequently, the third family of compact stars appear in the mass-radius relations of hybrid stars in the narrow scope of the bag constant from 175 MeV to 180 MeV. These show that the choice of the bag constant in the MIT bag model has significant influence on the properties of hybrid stars. 相似文献
20.
Shaoyu Yin Jiadong Zang Ru-Keng Su 《The European Physical Journal A - Hadrons and Nuclei》2010,43(3):295-301
The equations of state for neutron matter, strange and non-strange hadronic matter in the chiral SU(3) quark mean-field model are applied in the study of slowly rotating neutron stars and hadronic stars. The radius, mass,
moment of inertia, and other physical quantities are carefully examined. The effect of the nucleon crust for the strange hadronic
star is exhibited. Our results show that the rotation can increase the maximum mass of compact stars significantly. For a
big enough mass of pulsars which cannot be explained as strange hadronic stars, theoretical approaches to increase the maximum
mass are addressed. 相似文献