标量场的动量与宇宙波函数

我们用有限维超空间模型分析了标量场的动量对宇宙波函数的影响。指出经典禁戒区的范围与动量值密切相关;在一定的条件下,在α～0附近区域内会出现经典允许区;波函数的行为与算符顺序因子p有关。使用Vilenkin边条件,我们得出α一定时波函数随标量场φ的分布几率不依赖φ,这与忽略标量场的动量时算出的分布几率不同,因此对于剧胀宇宙的初条件的推断也不同。最后,我们把所得的结果与经典剧胀理论进行了比较。     

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。     

含αR~2+γR_(μν)R~(μν)项的宇宙暴涨

我们利用含αR~2+γR_(μv)R~(μv)项的宇宙理论同带有一个标量场φ的Einstein理论之间的等价性,讨论了该宇宙的暴涨行为.结果表明,在D维空时(D>2)中,存在指数型的暴涨解.     

宇宙常数Λ≠0的平面引力波

本文讨论了宇宙常数Λ≠0时的平面引力波问题。在弱场近似下,得到了平面引力波传播方程及色散方程。通过对Kretschmann曲率标量的讨论发现,不同于Λ=0时h_(μv)仅有横场这一众所周知的结果,Λ<0时不存在一个坐标系,使h_(μv)的标量场、纵场、混合场分量全为零。最后讨论引力波辐射,结论是与Λ=0时无偶极辐射这一结果不同,Λ<0时,混合场的辐射有偶极辐射。     

星系内禀指向对弱引力透镜剪切场信号污染的去除方法

星系的内禀指向(intrinsic alignment, IA)的关联性是弱引力透镜观测中剪切场信号的一个重要系统误差,人们在之前的弱引力透镜研究中已经提出了许多修正该误差的方法。从数据处理方面,人们可以剔除物理距离比较近的星系对,但是这种方法只能近似消除星系内禀指向自相关带来的污染项,并不能消除星系内禀指向与周围物质密度场的相关性,并且这种方法也会丢失很多星系的信息。而目前弱引力透镜观测中广泛使用的IA模型与实际的IA模型可能相差甚远,使用不同的IA模型得到的宇宙学参数会存在很大差别。虽然零调(nulling)技术不用假设IA模型,但是这种技术仅能消除星系内禀指向与周围物质密度场的相关性。另外,由于这种技术须对红移设置不同的权重,所以会失去IA对红移的依赖性。Zhang^[1, 2]提出的自修正方法,在不假设任何IA模型的情况下,利用多种观测量以及几个物理量之间的比例关系就能够把弱引力透镜中的IA信号很好地消除。此自修正方法可望广泛应用于即将开始的第四代弱引力透镜巡天中。     

Abell团相关性-富度关系的统计研究

本文对D≤4,R≥0的Abell团样品和整个R≥3的Abell团样品的空间两点相关函数做了统计分析,结果表明R≥0,R=0和R≥3的Abell团的相关函数分别为175r~(-1.8),150r~(-1.8)和1900r~(-1.8)利用已有的R≥1和R≥2团的相关函数的统计结果,我们得到了Abell团的相关性幅度α与富度N之间的关系:α∝N~(1.6)。在相关性幅度的统计误差所允许的范围内,α与N之间的关系可以在宇宙弦理论中得到解释。     

Bianchi型宇宙的量子化

本文将Ｗｈｅｅｌｅｒ—ＤｅＷｉｔｔ方程的平方根形式用于具有辐射场源的Ｂｉａｎｃｈｉ—Ⅰ型宇宙组成的微超空间模型，由此导出一个具有守恒流和正定几率密度的宇宙波函数．本文探讨了Ｂｉａｎｃｈｉ型宇宙的３次量子化，把类似于弯曲时空中量子场论程序应用到各向异性的Ｂｉａｎｃｈｉ—Ⅲ型宇宙中，给出了Ｗｈｅｅｌｅｒ—ＤｅＷｉｔｔ方程所满足的宇宙波函数解．把波函数作为微超空间中宇宙场算符看待后，不仅能解决量子宇宙学中几率解释的困难，而且也能得到宇宙多次产生的结论．同时估算了各种宇宙从“无”产生平均数目，给出了宇宙生成的分布，发现它遵从Ｐｌａｎｃｋ分布．     

等离子体湍动电场对Stark致宽函数的贡献

过去在用Stark效应研究天体活动过程的光谱时,一般仅考虑Holtsmark场的作用,所得出的电子密度只是一个上限。近来的研究表明,等离子体湍动电场在其中也起着重要的作用,而且当计及这种场的作用时,电子密度减小很多。本文给出Balmer线从H_3—H_(30)的Stark致宽函数S(α,α),它们是考虑到Holtsmark场和湍动场的联合作用以及对两者的不同比值而计算的,所给出的结果与Underhill等和Galdetskii等分别对纯Holtsmark场和纯湍动场而得到的类似数值不同。由于除了极少数外,大部分太阳耀斑和爆发日珥以及其他天体活动过程可能都处于弱或中等等离子体湍动状态,因而所算出的S(α,α)值可用于这些过程的氢线轮廓或半宽的分析。     

大尺度质量扰动和速度场的计算

本文在宇宙弦模型中,计算了各种暗物质主导宇宙的大尺度均方质量扰动和速度场。我们的计算结果表明,如果冷暗物质和重子主导字苗在8Mpch~(-1)处引力成团达到非线性或者中微子主导宇宙在z～3时出现Pancake碎裂,则相应的宇宙弦线密度μ均应满足关系式:Gμ>10~(-5),而这样的弦密度将导致宇宙微波背景较大的各向异性并违反大爆炸核合成理论。对大尺度速度场的计算,我们得到了它随距离增大比通常宇宙模型下降得更慢的结果,但它仍不足以解释Collins等最近报告的在50h~(-1)Mpc处v_p=970±300km·s~(-1)的固有速度。因此我们的计算表明,由单一的弦扰动形成观测到的大尺度结构是困难的。双扰动模型有可能是解决困难的一种途径。     

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。     

Quantization of the Bianchi type universe

In this paper, we have used a square root formulation of the Wheeler-De Witt equation to quantize a minisuperspace model consisting of the Bianchi-I type universe with a radiation field source. We have derived a wavefunction with a conserved current and a positive-definite probability density.

We have also explored the third quantization of the Bianchi type universe using a procedure usual in the quantum field theory of curved space-time. We have given the wave function that satisfies the Wheeler-De Witt equation. By regarding the wave function as the universe field operator in a minisuperspace, we have not only circumvented the difficulty of a probabilistic interpretation in quantum cosmology, we have also reached the conclusion that multiple universes would result. We have estimated the average number of universes produced from ‘nothing’, and have given their distribution, which turned out to be a Planck distribution.     

The wave function of the universe in the superstring theory

Wave function of the universe in the superstring theory is discussed and using Vilenkin's boundary condition, the probability density of the scale factor a at a given value of the dilaton field, is obtained. It is shown that when the universe spontaneously nucleates, the minimum value of the scale factor of the classical universe is of the order of the Planck length, that is, quantum effects can prevent the universe from collapsing to a single point.     

Nonlinear spinor field in Bianchi type-I Universe filled with viscous fluid: numerical solutions

We consider a system of nonlinear spinor and a Bianchi type I gravitational fields in presence of viscous fluid. The nonlinear term in the spinor field Lagrangian is chosen to be λ F, with λ being a self-coupling constant and F being a function of the invariants I an J constructed from bilinear spinor forms S and P. Self-consistent solutions to the spinor and BI gravitational field equations are obtained in terms of τ, where τ is the volume scale of BI universe. System of equations for τ and ε, where ε is the energy of the viscous fluid, is deduced. This system is solved numerically for some special cases.      

Cosmic energy equation and clustering of non-point mass system of galaxies

Cosmic energy equation is an important equation for studying the gravitational galaxy clustering in the expanding universe. We derive the distribution function for fluctuations in particle number by using the cosmic energy equation for extended structures (galaxies with halos). From spatial distribution function, containing particle fluctuations, we derive the velocity distribution function to understand the influence of particle fluctuations on the velocities of galaxies.With the help of cosmic energy equation we try to find out the physical constraints for the application of quasi-equilibrium approximation.     

Thermodynamic study of non-linear electrodynamics in loop quantum cosmology

In this work, we have discussed the Maxwell’s electrodynamics in non-linear forms in FRW universe. The energy density and pressure for non-linear electrodynamics have been written in the electro-magnetic universe. The Einstein’s field equations for flat FRW model in loop quantum cosmology have been considered if the universe is filled with the matter and electro-magnetic field. We separately assumed the magnetic universe and electric universe. The interaction between matter and magnetic field have been considered in one section and for some particular form of interaction term, we have found the solutions of magnetic field and the energy density of matter. We have also considered the interaction between the matter and electric field and another form of interaction term has been chosen to solve the field equations. The validity of generalized second law of thermodynamics has been investigated on apparent and event horizons using Gibb’s law and the first law of thermodynamics for magnetic and electric universe separately.     

Noncommutative branch-cut quantum gravity with a self-coupling inflaton scalar field: The wave function of the Universe

This article focuses on the implications of a noncommutative formulation of branch-cut quantum gravity. Based on a mini-superspace structure that obeys the noncommutative Poisson algebra, combined with the Wheeler–DeWitt equation and Hořava–Lifshitz quantum gravity, we explore the impact of a scalar field of the inflaton-type in the evolution of the Universe's wave function. Taking as a starting point the Hořava–Lifshitz action, which depends on the scalar curvature of the branched Universe and its derivatives, the corresponding wave equations are derived and solved. The noncommutative quantum gravity approach adopted preserves the diffeomorphism property of General Relativity, maintaining compatibility with the Arnowitt–Deser–Misner Formalism. In this work we delve deeper into a mini-superspace of noncommutative variables, incorporating scalar inflaton fields and exploring inflationary models, particularly chaotic and nonchaotic scenarios. We obtained solutions to the wave equations without resorting to numerical approximations. The results indicate that the noncommutative algebraic space captures low and high spacetime scales, driving the exponential acceleration of the Universe.     

Interacting new agegraphic dark energy in a cyclic universe

The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase (ω<−1), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of Li et al. (Adv. High Energy Phys. 2009: 905705, 2009), which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.     

The branch-cut quantum gravity with a self-coupling inflation scalar field: The wave function of the Universe

This paper focuses on the implications of a commutative formulation that integrates branch-cutting cosmology, the Wheeler–DeWitt equation, and Hořava–Lifshitz quantum gravity. Building on a mini-superspace structure, we explore the impact of an inflaton-type scalar field on the wave function of the Universe. Specifically analyzing the dynamical solutions of branch-cut gravity within a mini-superspace framework, we emphasize the scalar field's influence on the evolution of the evolution of the wave function of the Universe. Our research unveils a helix-like function that characterizes a topologically foliated spacetime structure. The starting point is the Hořava–Lifshitz action, which depends on the scalar curvature of the branched Universe and its derivatives, with running coupling constants denoted as $g_i$. The corresponding wave equations are derived and are resolved. The commutative quantum gravity approach preserves the diffeomorphism property of General Relativity, maintaining compatibility with the Arnowitt–Deser–Misner formalism. Additionally, we delve into a mini-superspace of variables, incorporating scalar-inflaton fields and exploring inflationary models, particularly chaotic and nonchaotic scenarios. We obtained solutions for the wave equations without recurring to numerical approximations.     

Status of physical observables of a friedmann universe in the classical and quantum hamiltonian formalisms

The paper is devoted to an investigation of the relationships between the classical Friedmann cosmology and the Dirac Hamiltonian approach to quantization of the universe, based on the simple but important example of a homogeneous universe filled with excitations of a scalar field. The method of gaugeless reduction is used to completely separate the sector of physical variables from the purely gauge sector, making it possible to find the relationship between cosmological observables in the Friedmann — Einstein sense and observables of the Dirac Hamiltonian formalism in the Narlikar conformai reference frame. Gaugeless reduction enabled us to establish that in the process of reduction, one of the variables of the nonphysical sector is converted into an invariant time parameter and cannot be treated as a dynamical variable in either the functional or the operator approach to quantization. It is shown that in this conversion of a variable into a time parameter, the Hartle-Hawking functional integral is the reason why the wave function of the Wheeler—De Witt (WDW) equation cannot be normalized and why an infinite gauge factor arises. The gaugeless reduction provides a certain recipe for mathematical and physical interpretation of the WDW equation and wave functions, the use of which makes their relationship to observational cosmology clear and transparent. It is shown, in particular, how the WDW wave function describes the Friedmann evolution with respect to proper time. Translated from Astrofizika, Vol. 40, No. 2, pp. 303–321, April–June, 1997.