温度对有中微子束缚的致密物质性质的影响

把FST模型应用于温度对有中微子束缚的致密物质性质的研究中.结果表明中微子的束缚使得致密物质系统中的质子含量有所增加,温度对npe系统(无中微子束缚)的质子含量的影响比其对npeν_e系统(有中微子束缚)的影响明显.温度的升高使两个系统的能量密度都有所升高,同时,由它们所组成的前中子星的最大质量和Kepler周期都有一定程度的下降.     

新生中子星的性质与三体核力效应

在Brueckner-Hartree-Fock理论框架内, 研究了新生中子星的状态方程和性质, 计算了新生中子星的最大质量和新生中子星中质子占总核子数的丰度, 特别是讨论了三体核力和中微子束缚效应的影响以及三体核力和中微子束缚效应的相互影响. 结果表明, 无论是否考虑三体核力, 中微子束缚对新生中子星的状态方程和质子丰度均有明显影响. 中微子束缚导致新生中子星物质中的质子丰度显著增大. 三体核力的贡献是使新生中子星的状态方程变硬并导致新生中子星中质子丰度明显增大. 束缚在中子星物质中的中微子显著减弱了三体核力对于中子星物质中质子丰度的影响.     

强磁场中修正URCA过程的中微子产能率

基于n-p-e模型并考虑修正URCA过程中的质子分支,研究了强磁场对中子星核心区域修正URCA过程中微子产能率的影响.结果表明,强磁场使修正URCA过程的中微子产能率产生明显振荡;与中子分支相比,强磁场对质子分支中微子产能率的影响偏弱,但是它将提高总的中微子产能率.所得结论将有助于进一步研究中子星的冷却机理. 关键词： 中子星 强磁场 修正的URCA过程     

前中子星内的K-凝聚和超子的生成

用相对论平均场下的手征强子模型研究了前中子星内K^-凝聚和超子的生成。结果显示，前中子星内的中微子束缚使得出现K^-凝聚的临界密度推迟到更高的重子密度，而K^-0凝聚无法出现。同时中微子束缚使得前中子星的状态方程变硬，从而前中子星的最大质量变大。如果考虑超子，前中子星内无法出现K^-凝聚，同时系统的状态方程变软（与不含超子的情况相比），从而对应前中子星的最大质量变小。A chiral hadronic model is extended to investigate antikaon condensation and hyperons production of protoneutron stars. Our results show that neutrino trapping makes the critical density of K^- condensation delay to higher density and K^-0 condensation not occur. Meanwhile, the equation of state （EOS） of （proto）neutron star matter considering neutrino trapping is stiffer than the case without neutrino trapping. Therefore the maximum masses of rotoneutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are considered, antikaon condensation does not appear in （proto） neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of （proto）neutron stars are smaller than those without hyprons.     

中子星内部非奇异-奇异夸克物质的相变

研究了中子星内部从两味夸克物质到三味夸克物质的相变过程。发现这个过程的时标短至10^-7s,并且在相变中奇异夸克所参加的半轻子过程是中微子能量损失的主要过程。这样,1.4M_⊙质量的中子星内部的非奇异-奇异夸克物质相变会有几个10⁵¹erg的能量以中微子形式发射出去,这将表现为一种中微子爆现象。     

发现最大质量中子星影响深远

如果中子星可具有两倍的太阳质量,大多数曾经猜测的奇特致密物质状态是不会存在的.中子星拥有宇宙中最致密的物质.它们是星核塌缩超新星爆发的残骸,将超过太阳质量(M⊙)的物质挤压至直径小于30km的球内.密度极高的这种物质不能在实验室内     

奇异星的冷却

从奇异夸克物质的热力学巨势出发计算了奇异星的组份，得到电子丰度随强相互作用耦合常数或奇异物质的密度增大而减小．利用弱电统一理论，推导了奇异物质的中微子能量损失率。通过研究有薄壳的均匀奇异星和中子垦的冷却过程，得到年轻奇异星的表面温度比同年代的中子星的表面温度低得多，这可以作为区别奇异星与中子星的观测途径。 关键词：     

中子星物质中的K介子凝聚与三体核力效应

利用Brueckner-Hartree-Fock方法，计算了β稳定中子星物质的状态方程以及三体核力的影响，特别是研究了三体核力对中子星物质中K介子凝聚的影响. 结果表明三体核力对β稳定中子星物质中出现K介子凝聚的临界密度以及中子星物质中各种粒子所占的比例均有重要影响. 三体核力的主要作用是降低了中子星物质中出现K介子凝聚的临界密度并使K凝聚相中的核物质更加接近于对称核物质.     

中子星中质子比例的密度依赖

利用Hartree-Fock理论,基于扩展的Skyrme有效相互作用,采用抛物线近似下对称能的密度相关形式以及β平衡和电中性条件,给出了中子星中质子比例的密度依赖关系.通过比较不同的势参数SII,SIII,SKM和SKI5下对称能强度系数的密度依赖关系研究了中子星中的质子比例,发现在高密时势参数SII,SIII和SKM能够给出中子星中质子消失的结果,这预示着致密核物质可能存在纯中子物质的基态.同时计算表明,考虑中子星中μ^－子的贡献后使质子比例增加.     

超强磁场对中子星外壳层核素56Fe,56Co,56Ni,56Mn和56Cr电子俘获过程中微子能量损失的影响

研究了超强磁场对中子星外壳层核素⁵⁶Fe,⁵⁶Co,⁵⁶Ni,⁵⁶Mn和⁵⁶Cr电子俘获过程中微子能量损失的影响.结果表明,就大部分中子星表面的磁场B<10¹³G,超强磁场对中微子能量损失率的影响很小.对于一些磁场范围为10¹³—10¹⁵G的超磁星,超强磁场可使中微子能量损失率大大降低,甚至超过5个数量级.     

Nonextensive statistical effects in protoneutron stars

We investigate the bulk properties of protoneutron stars in the framework of a relativistic mean-field theory based on nonextensive statistical mechanics, characterized by power-law quantum distributions. We study the relevance of nonextensive statistical effects on the b \beta -stable equation of state at fixed entropy per baryon, in the presence and in the absence of trapped neutrinos, for nucleonic and hyperonic matter. We show that nonextensive statistical effects could play a crucial role in the structure and in the evolution of the protoneutron stars also for small deviations from the standard Boltzmann-Gibbs statistics.     

Equation of State of Protoneutron Star with Trapped Neutrinos

The influence of trapped neutrinos on the proto-neutron star is studied in the framework of relativistic mean-field theory. The results show that trapped neutrinos increase proton fraction and make the equation of ๏๏ state of neutron star matter softer when neglecting hyperonic freedom, while suppress the appearance of hyperons and make the equation of state stiffer when including hyperons in the protoneutron star. The maximum mass, compared with cold neutron star which is in beta equilibrium, decreases by 0.06_{M_{\odot}} for non-strange protoneutron star while increases by 0.21_{M_{\odot}} for protoneutron star with hyperons when the relative number of trapped neutrino is 0.4.     

超子耦合参数对热前中子星物质的影响

在相对论平均场理论框架内,利用Λ超子的结合能和中子星质量的观测数据得到超子标量介子耦合参数χσ的范围是0.33—0.77。在这个范围内, 研究了χσ取不同值时, 包含核子, Λ和Ξ超子的热前中子星（固定单个重子熵s=1）的性质。结果表明, 如果超子耦合参数变大, 前中子星核心温度变高, 中微子丰度变低, 前中子星的亚稳态质量范围变小。如果χσ超过了0.75, 前中子星不可能演变成黑洞。联系SN1987A讨论了这一结果的意义。In the framework of the relativistic mean field theory(RMFT), protoneutron stars with hyperons are studied. To be compatible with neutron star masses, the hyperon scalar coupling χσ should lie in the range of 0.33—0.77. As the hyperon scalar coupling increases, in protoneutron star matter, the core temperature increases whereas the abundance of neutrinos decreases. The metastable mass range of protoneutron stars narrows as the temperature increases. It is found that a protoneutron star cannot subside into a low mass black hole when χσ>0.75. Furthermore, the case of SN1987A is discussed.     

Strangeness in stellar matter

A protoneutron star is formed immediately after the gravitational collapse of the core of a massive star. At birth, the hot and high density matter in such a star contains a large number of neutrinos trapped during collapse. Trapped neutrinos generally inhibit the presence of exotic matter — hyperons, a kaon condensate, or quarks. However, as the neutrinos diffuse out in about 10–15 s, the threshold for the appearance of strangeness is reduced; hence, the composition and the structure of the star can change significantly. The effect of exotic, negatively-charged, strangeness-bearing components is always to soften the equation of state, and the possibility exists that the star collapses to a black hole at this time. This could explain why no neutron star has yet been seen in the remnant of supernova SN1987A, even though one certainly existed when neutrinos were detected on Feb. 23, 1987. With new generation neutrino detectors it is feasible to test different theoretical scenarios observationally.     

Antikaon Condensation and In-medium Kaon and Antikaon Production in Protoneutron Stars

Antikaon condensation and kaon and antikaon production in protoneutron stars are investigated in a chiral hadronic model （also referred to as the FST model in this paper）. The effects of neutrino trapping on protoneutron stars are analyzed systematically. It is shown that neutrino trapping makes the critical density of K^- condensation delay to higher density and fifo condensation not occur. The equation of state （EOS） of （proto）neutron star matter with neutrino trapping is stiffer than that without neutrino trapping. As a result, the maximum masses of （proto）neutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are taken into account, antikaon does not form a condensate in （proto）neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of （proto）neutron stars are smaller than those without hyprons. Finally, our results illustrate that the Q values for K^＋ and K^- production in （proto）neutron stars are not sensitive to neutrino trapping and inclusion of hyperons.     

Thermal Dynamics Behavior of Protoneutron Star Matter

In the relativistic σ-ω model, including the vacuum fluctuation of nucleons and σ mesons, the effect of the temperature to the composition and equation of state of protoneutron star matter, nucleon effective mass and chemical potential of neutrons and electrons are studied. We find that the influence of the temperature on the equation of state of protoneutron star matter is indeed small, however, its influence on the composition of protoneutron star, which will contribute to the evolution of protoneutron star, cannot be neglected in low density region. The chemical potentials of neutrons and electrons also depend on the temperature in almost the same density region.     

Neutrinos and explosive nucleosynthesis

Core-collapse supernovae produce a hot protoneutron star that cools emitting huge amounts of neutrinos of all flavors. The interaction of these neutrinos with the outer layers of the protoneutron star produces an outflow of matter whose composition is determined by the luminosities and energies of the emitted neutrinos and antineutrinos. The presence of light nuclei like deuterons and tritons can have a big impact in the average energies of the emitted antineutrinos and consequently in the neutron-richness of the ejected matter. Recent hydrodynamical models show that the ejected matter is in fact proton-rich and constitutes the site of the νp-process where antineutrino absorption reactions catalyze the nucleosynthesis of nuclei with A>64.     

Neutrino signals from the formation of a black hole: A probe of the equation of state of dense matter

The gravitational collapse of a nonrotating, black-hole-forming massive star is studied by nu-radiation-hydrodynamical simulations for two different sets of realistic equation of state of dense matter. We show that the event will produce as many neutrinos as the ordinary supernova, but with distinctive characteristics in luminosities and spectra that will be an unmistakable indication of black hole formation. More importantly, the neutrino signals are quite sensitive to the difference of equation of state and can be used as a useful probe into the properties of dense matter. The event will be unique in that they will be shining only by neutrinos (and, possibly, gravitational waves) but not by photons, and hence they should be an important target of neutrino astronomy.