混杂星结构限制与化学加热机制研究

发布时间：2018-05-25 14:40

本文选题：中子星 + 夸克物质　；参考：《华中师范大学》2012年博士论文

【摘要】：一般认为,脉冲星是由超密核物质构成的致密天体(中子星),但其内部物质成分到底如何至今仍在探索中。中子星理论模型与观测对比研究是探究中子星内部致密物质性质的重要手段,本文在第一章介绍了中子星内部结构及各种理论模型,并讨论了各种观测(最大质量、表面热辐射、质量-半径关系等)对理论模型的限制。近年来一些研究结果表明,中子星内极有可能存在奇异夸克物质。随着地面高能核物理的发展,高能重离子碰撞实验也预示夸克物质的存在,含有奇异夸克物质的中子星理论模型研究显得日益重要。本文第二章介绍了描述夸克物质的主要状态方程,重点研究了最新中子星最大质量观测结合奇异夸克物质稳定存在的物理条件,对奇异星内夸克物质状态方程的限制,发现奇异星模型与观测并不矛盾。对于密度依赖质量模型描述的非色超导奇异星,最大质量对参数C更为敏感,在参数允许范围内,夸克星的最大质量最大可达到2.25M& ,这一最大质量可以解释大质量中子星的观测值；而对于CFL奇异星,较大的s夸克质量,需要更大的色超导能隙值,尽管可以通过提高能隙值而获得更大的CFL奇异星质量,但是s夸克质量仍然在决定奇异星质量中起到重要作用。与以往研究利用质量-半径关系对状态方程进行排除不同,我们计算模拟了奇异星最大质量随两个状态方程参数连续变化的情况,给出了对状态方程参数的明确限制。表面热辐射观测是探寻中子星内部物态及相关物理过程机制的另一重要途径。随着Chandara和XMM-Newton的升空,加之ROSAT巡天,中子星热辐射观测和研究有了显著的进展。最新的来自XMM-Newton的观测显示,几颗处于光子冷却阶段的年老(大于105年)中子星(PSR B2224+65,PSRJ2043-2740,PSR B0628-28,PSR B1929+10)出现老年高温行为,而这些星体的解释需要加热机制的支持。本文在第三章介绍了中子星热演化的基本理论,并对星体内各种主要的加热机制进行了对比分析,其中化学加热机制是解释老年中子星高温行为最为重要的加热机制。化学加热机制源于中子星转动减慢过程中,星体内各种弱作用反应平衡的偏离。因为引发化学偏离的转动时标要比恢复平衡的弱反应时标快,系统始终处于非平衡状态,化学不平衡储存的化学能通过反应转化为热能加热星体。第四章在介绍了中子星内化学偏离及化学加热机制发生的物理过程后,重点作了以下工作。计算了非平衡态下色超导夸克物质弱过程的反应率和中微子辐射率。计算表明反应同时受到化学偏离量和色超导的影响,有趣的是化学偏离会加快夸克物质Urca过程反应率提高中微子辐射率,而色超导因为压缩了粒子的相空间而起到完全相反的作用。当化学偏离量较小时,色超导抑制了Urca过程的中微子反应率,抑制的程度与色超导的能隙大小有关,但是随着化学偏离量的增大,当偏离量达到能隙大小附近时,抑制作用被快速完全破坏,反应的中微子辐射率被大幅提升恢复至没有色超导时的情况。计算结果对于研究含色超导夸克物质的热演化问题十分重要。研究了中子星内核子的退禁闭相变对化学偏离的重要影响,在均匀混杂星模型下计算化学偏离量和表面温度演化情况,结果表明退禁闭相变加剧了中子星内各粒子的化学偏离程度,并明显提升化学加热的加热效率,加热效应更早出现。而且当星体内的核子分别发生直接Urca过程和修改Urca过程时,混合相中夸克、核子对热演化过程的主导地位并不相同。化学加热机制的研究提示我们,以往的研究主要考虑星体处于各种平衡态,而实际上非平衡态才是旋转中子星内的常态,非平衡态下中子星内的物理图象也与以往不同,可能出现一些新的物理现象和效应,这为我们以后的研究提供方向。
[Abstract]:It is generally believed that the pulsar is a compact celestial body (the neutron star) composed of superdense nuclei, but how the internal material composition is still exploring. The theoretical model of the neutron star and the observation and contrast study are the important means to explore the properties of the dense matter inside the neutron star. In the first chapter, the internal structure and various theories of the neutron star are introduced. Models, and the limitations of theoretical models on various observations (maximum mass, surface heat radiation, mass radius relations, etc.) are discussed.
In recent years, some research results show that there is a possible existence of singular quark matter in the neutron star. With the development of high energy nuclear physics on the ground, high energy heavy ion collision experiments also indicate the existence of quark matter. The theoretical model of neutron star containing singular quark matter is becoming more and more important. The second chapter introduces the main description of quark matter. For the state equation, we focus on the physical conditions of the maximum mass observation of the latest neutron star combined with the physical conditions of the singular quark matter, and the limitation of the state equation of the quark matter in the singular star. It is found that the singular star model is not contradictory to the observation. For the non chromatic superconducting singularity described by the density dependent mass model, the maximum mass to the parameter C is more. In the range of parameters, the maximum mass of the quark star can reach 2.25M&. This maximum mass can explain the observational value of the mass neutron star, and for the CFL singular star, the larger s quark mass requires a larger color superconducting gap value, although the mass of the CFL singularities can be obtained by raising the high energy gap value, but s The mass of quarks still plays an important role in determining the mass of singular stars. It is different from the previous study of the relationship between the mass radius and the equation of state. We calculate and simulate the continuous variation of the maximum mass of a singular star with the parameters of the two state equation, and give a definite limit to the parameter of the state.
The observation of surface thermal radiation is another important way to explore the internal state and related physical process mechanism of neutron stars. With the lift of Chandara and XMM-Newton and the ROSAT patrol, the observation and research of neutron star thermal radiation have made remarkable progress. The latest observations from XMM-Newton show that several years of aging in the phase of photon cooling (greater than 10) 5 years) the neutron stars (PSR B2224+65, PSRJ2043-2740, PSR B0628-28, PSR B1929+10) have high temperature behavior in the aged, and the explanation of these stars needs the support of the heating mechanism. In this paper, the basic theory of thermal evolution of neutron stars is introduced in the third chapter, and the main heating mechanisms in the stars are compared and analyzed, in which the mechanism of chemical heating is Explain the most important heating mechanism of the high temperature behavior of the neutron star in the old age.
The mechanism of chemical heating is due to the deviation of the equilibrium of various weak reactions in the star body during the rotation of the neutron star. Because the rotation time of the chemical deviation is faster than the weak reaction of the recovery equilibrium, the system is always in the nonequilibrium state and the chemical energy stored by chemical imbalance is converted into heat through the reaction to heat the star. The fourth chapter is After introducing the physical process of neutron star chemical deviation and the mechanism of chemical heating, the following work is emphasized.
The reaction rate and the neutrino emissivity of the weak process of the superconducting quark matter in the nonequilibrium state are calculated. The calculation shows that the reaction is influenced by the chemical deviation and the color superconductivity. It is interesting that the chemical deviation will accelerate the reaction rate of the quark matter Urca process to increase the neutrino radiant rate, and the color superconductor acts as the phase space of the particle. When the chemical deviation is small, color superconductivity inhibits the neutrino reaction rate in the Urca process, and the degree of inhibition is related to the energy gap size of the color superconductor, but with the increase of the chemical deviation, when the deviation reaches the gap size, the inhibition is rapidly completely destroyed and the neutrino radiation rate of the reaction is greatly raised. It is important to study the thermal evolution of color superconducting quark matter.
The important effect of the retrograde phase transition on the chemical deviation in the neutron star nucleus is studied. The chemical deviation and the surface temperature evolution are calculated under the uniform hybrid star model. The results show that the closed phase transition intensifies the chemical deviation of the particles in the neutron star, and obviously improves the heating efficiency of the chemical heating, and the heating effect appears earlier. In addition, when the nucleons in the body occur direct Urca process and modify the Urca process, the dominant position of the quarks and nucleons in the thermal evolution process is different in the mixed phase. The study of chemical heating mechanism suggests that the previous studies mainly consider the stars in various equilibrium states, but the nonequilibrium state is the constant in the rotating neutron star. The physical images of the neutron stars in the state and the nonequilibrium state are different from the previous ones, and some new physical phenomena and effects may appear, which provides the direction for our future research.
【学位授予单位】：华中师范大学
【学位级别】：博士
【学位授予年份】：2012
【分类号】：P145.6

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