四维稳态伪Riemann时空中的Dirac粒子束缚态

在本中，我们在一般的四维稳态伪Riemann时空中讨论了Dirac粒子的束缚态问题。用零标架方法计算了旋系数，导出了Dirac方程，在视界曲面附近解了Cirac方程，得到了Dirac粒子四分量波函数显示表达式，发现在视界曲面附近，该解是具有无限个节点的共振态解，从而推知，具有非简并视界的四维稳态伪Riemann时空一般不可能存在Dirac粒子束缚态。     

动态Dilaton—Maxwell黑洞中Dirac粒子的Hawking辐射

给出了动态Dilaton-Maxwell黑洞背景下Dirac方程的退耦与分离变量,并通过适当的变换在动态Dilaton-Maxwell黑洞的视界附近找到了静止质量不为零的Dirac方程的有物理意义的解,导出了Hawking热谱公式、辐射温度和视界面方程。从而解决了Dirac粒子在Dilaton-Maxwell黑洞背景下Hawking蒸发的问题。     

宇宙γ射线暴的一种可能产能机制

本文对宇宙r射线暴的能源提出了一个模型。按照这种模型,等离子体的不稳定过程包含两个相,即热暴发相和稳定湮灭相。而贮存在局部源中的磁能,以一种与观测相一致的速率有效地转换为等离子体的动力能和欧姆耗散能。随着反常阻抗的快速增加,建立了等离子体的湍动场。它与麦克思韦高能尾巴电子迅速耦合,产生了相对论性电子。r射线能够通过相对论性电子在磁场中的同步辐射而得到说明。     

小角动量Kerr度规中的Dirac方程与准束缚能级

本利用Bergman-Brill-Wheeler方法，给出了小角动量Kerr度规中的Dirac方程的Hamiltonian形式，并计算了小角动量对于准束缚能级的影响。     

等离子体天体物理中的弱湍动和强湍动

本文对等离子体天体物理中的弱及强湍动进行评述,并强调了等离子体的基本相互作用。 弱湍动的主要课题是波—波、波—粒子间的非线性相互作用;相互作用的动力学方程组可用半经典方法导出。讨论了如下重要课题:弱非均匀性介质中波的传播方程,湍动加速和磁发电机制。 分析了控制强湍动现象的查哈罗夫方程。讨论了一些天体物理中的重要问题,例如宇宙天体中自生磁场、电双层、孤波加速、辐射以及爆发等等。     

宇宙信息

宇宙信息星系研究的新进展今天天文学家利用空间望远镜已经较为深入地考察了年龄在１００～１５０亿年的宇宙。虽然宇宙微波背景图提供了宇宙幼年时期的一幅模糊图象，然而天文学家对星系是在什么时候和怎样形成的仍感困惑。星系演化难题中的一个关键部分已经通过《哈勃深...     

在Kerr-Newman时空中Dirac粒子的Hawking蒸发

本文得到了Kerr-Newman黑洞视界附近Dirac方程的解,并与Klein-Gordon方程的解作了比较。把刘辽、许殿彦的工作首先从准极端Kerr黑洞推广到准极端Kerr-Newman黑洞,然后又进一步推广到一般Kerr-Newman黑洞,从而证实了一般Kerr-Newman黑洞辐射的Dirac粒子的能谱具有黑体辐射的形式。     

脉冲星、中子星和奇异星的故事

在茫茫宇宙中,什么天体的质量堪比太阳而大小还比不上北京城区(图1)?什么天体的旋转速度可以赛过陀螺?什么天体有胜过地球百万亿倍的超级磁场?它就是脉冲星,一个有着与太阳相当的质量而半径却只有十千米左右的致密天体。     

超弦理论中的宇宙波函数

本文讨论了超弦理论中的宇宙波函数，使用Ｖｉｌｅｎｋｉｎ的边界条件，我们得到了膨胀子场Ｄ的值给定时宇宙标度因子ａ的几率分布。我们还得到了宇宙自发成核时，经典宇宙的标度因子的最小值为Ｐｌａｎｃｋ长度的数量级，这说明量子效应能阻止宇宙塌缩到奇点。     

冕洞磁场研究的现状

冕洞是太阳大气日冕层中的现象。近代太阳大气物理性质的研究表明,磁场起着重要的作用。就日冕层来说,磁场明显地起两个作用:一个作用是日冕中的一些现象因贮存在磁场中的磁能积聚而产生;另一个作用是磁场沟通了日冕的物质流和能流。同样,冕洞磁场强度的大小及其位形,对冕洞的物理性质有重要影响。 本文的目的是叙述冕洞磁场近代研究情况,从中看出发展趋势、基本思想、方法和主要结论,同时从中总结出存在的问题和需要深入进行的工作。 本文分四个方面作简要叙述:一、冕洞磁场的经验模式和计算模式;二、冕洞磁场在冕洞内的色球层和过渡区所起的作用;三、冕洞磁场的行星际效应;四、存在问题。     

Primordial magnetic field,inflation and cosmic strings

The possibility of a primordial magnetic field is discussed. The formation of closed, superconducting cosmic strings before the end of inflation is pointed out as a mechanism able to preserve a magnetic field inside the loops which could provide seeds for galactic magnetic fields.     

Cosmological magnetic fields: their generation,evolution and observation

We review the possible mechanisms for the generation of cosmological magnetic fields, discuss their evolution in an expanding Universe filled with the cosmic plasma and provide a critical review of the literature on the subject. We put special emphasis on the prospects for observational tests of the proposed cosmological magnetogenesis scenarios using radio and gamma-ray astronomy and ultra-high-energy cosmic rays. We argue that primordial magnetic fields are observationally testable. They lead to magnetic fields in the intergalactic medium with magnetic field strength and correlation length in a well defined range.We also state the unsolved questions in this fascinating open problem of cosmology and propose future observations to address them.     

List of forthcoming papers

This paper is largely a reply to Cowling's review of the present status of cosmic dynamo theory and its alternatives of primordial or fossil field models. Central is the question of turbulent diffusion, without which plasma dynamos will not work but primordial magnetic fields are retained. Turbulence does not shred or divide fields into small-scale elements as claimed; instead it creates these elements in addition to the large-scale field which remains after Ohmic diffusion has destroyed the small fields. The significance of the existence of a terrestrial dynamo is stressed and various objections to the existence of a solar-type dynamo are discussed, including the steady divergence of theory and observational evidence over a quarter century. Cowling's criticisms of the primordial field theory are discussed; these include turbulent diffusion, the timing of the solar magnetic cycle, and the importance attached to observations in active and quiet magnetic regions.Since this paper was communicated, a personal communication from Professor Cowling has partially resolved the difference of opinion about turbulent diffusion and its effects. This is discussed in a letter to the Editor, at the end of this volume, p. 477.     

The neutrino in the primordial magnetic field

We discuss the evolution of the massive Dirac particle in the cosmic magnetic field. The magnetic field makes the space metric anisotropic. By solving the Dirac equation we obtain the apparent magnetic moment of the neutrino in the cosmic magnetic field.     

Primordial magnetic fields in the post-recombination era and early reionization

We explore the ways in which primordial magnetic fields influence the thermal and ionization history of the post-recombination Universe. After recombination, the Universe becomes mostly neutral, resulting also in a sharp drop in the radiative viscosity. Primordial magnetic fields can then dissipate their energy into the intergalactic medium via ambipolar diffusion and, for small enough scales, by generating decaying magnetohydrodynamics turbulence. These processes can significantly modify the thermal and ionization history of the post-recombination Universe. We show that the dissipation effects of magnetic fields, which redshifts to a present value   B ₀= 3 × 10⁻⁹ G  smoothed on the magnetic Jeans scale and below, can give rise to Thomson scattering optical depths  τ≳ 0.1  , although not in the range of redshifts needed to explain the recent Wilkinson Microwave Anisotropy Probe ( WMAP ) polarization observations. We also study the possibility that primordial fields could induce the formation of subgalactic structures for   z ≳ 15  . We show that early structure formation induced by nanoGauss magnetic fields is potentially capable of producing the early reionization implied by the WMAP data. Future cosmic microwave background observations will be very useful to probe the modified ionization histories produced by primordial magnetic field evolution and constrain their strength.     

Galactic magnetic fields and their interactions with the gas and cosmic rays

(i) The controversy of dynamo or primordial origin of galactic magnetic fields is summarized and extended to show that the dynamo theory appears to fail. However, much more important than their origin are the characteristics of the fields and their interactions with the gas and cosmic rays. (ii) A passive magnetic field frozen into a turbulent plasma is not dissipated like a cloud of smoke (turbulent or eddy diffusion) as believed previously. On the contrary it is amplified exponentially until, within a few eddy periods, either the growing magnetic stresses halt the turbulence or the field becomes chaotic. Even if the Petschek reconnection mechanism operates, the field is always disordered to a scale <0.1L, whereL is the eddy dimension. The investigation may at last provide a semi-quantitative deductive theory of hydromagnetic eddies. (iii) It is concluded that the gas motions observed in our Galaxy are not convective but are mainly hydromagnetic waves or oscillations, with the magnetic field in control. The significance of this result is discussed in connection with the overall gas velocity field, the creation of stars and stellar systems, and with the origin and distribution of cosmic rays.     

Milestones in the Observations of Cosmic Magnetic Fields

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from anal     

Building the Fast Galactic Dynamo

In this paper we demonstrate the importance of cosmic rays for the dynamics of the interstellar medium. We present the first 3D-MHD numerical simulations of the Parker instability triggered by cosmic rays accelerated in randomly distributed supernova remnants. We show that in the presence of galactic rotation a net radial magnetic field is produced as a result of the cosmic ray injection and Coriolis force. This process provides a possibility of very efficient magnetic field amplification within the general frame of so called fast galactic dynamo proposed by Parker (1992).     

Non-linear amplification of a magnetic field driven by cosmic ray streaming

One-, two- and three-dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These show that cosmic ray streaming drives large-amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently transferred to the perturbed magnetic field of the Alfvén waves, and the non-linear time-scale of the growth of the waves is found to be very rapid, of the order of the gyro-period of the cosmic ray. Thus, a magnetic field of interstellar values, assumed in models of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic field reduces the cosmic ray acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant resolution to the highest energy Galactic cosmic ray problem, where the cosmic rays themselves provide the fields necessary for their acceleration.     

Non-Linear Amplification of a Magnetic Field Driven by Cosmic Ray Streaming

One dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These show that cosmic ray streaming drives large amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently transfered to the perturbed magnetic field of the Alfvén waves. Thus a magnetic field of interstellar values, assumed in models of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic field reduces the acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant resolution to the highest energy galactic cosmic ray problem were the cosmic rays themselves provide the fields necessary for their acceleration. This revised version was published online in July 2006 with corrections to the Cover Date.