Exact Scalar Field Inflationary Solution in Rainbow Universe

Using the Friedmann equation in rainbow Universe, we obtain an exact scalar field Inflationary Solution, which is a modification of the exact scalar field with negative potential −V ₀+m ² φ ²/2. Because the rainbow metric is Finsler metric, the result in this paper implies that the research of Finsler geometry in Cosmology should lead to several new physics theories.     

Role of Modified Chaplygin Gas in Bianchi Type-I Universe

We have studied the evolution of a homogeneous, anisotropic universe given by a Bianchi type-I cosmological model with modified Chaplygin gas. We have assumed that the equation of state of this modified model is valid from the radiation era to the ΛCMD model. We have used state-finder parameters in characterizing different phase of the model.     

The Planck Scale in the Universe

Extending the result of a previous paper, wherein elementary particles were considered to be an array of Planck scale oscillators, we show that the universe itself is the normal mode of a set of Planck scale oscillators.     

A Quantum Universe and the Solution to the Cosmological Problems

We have found that the hierarchial problems appearing in cosmology are a manifestation of the quantum nature of the universe. The universe is still described by the same formulae that once hold at Planck's time. The universe is found to be governed by the Machian equation, GM = Rc ², where M and R are mass and radius of the universe. A Planck's constant xsfor different cosmic scales is provided. The status of the universe at different stages is shown to be described in terms of the fundamental constants (c, , G, , H) only. The concept of maximal (minimal) acceleration, power, temperature, etc., is introduced and justified.     

Letter: A Model of Dark Energy for the Accelerating Universe

Recent observations of large scale structure of the Universe, especially that of Type Ia supernovae, indicate that the Universe is flat and is accelerating, and that the dominant energy density in the Universe is the cosmic dark energy. We propose a model in which the cosmic effective Yang-Mills condensate familiar in particle physics plays the role of the dark energy that causes the acceleration of the Universe. Since the quantum effective Yang-Mills field in certain states has the equation of state p _y = – _y , when employed as the cosmic matter source, it naturally results in an accelerating expansion of the Universe. With the matter components ( _m 1/3) being added into the model, the composition of YM condensate and matter components can give rise to the desired equation of state w –2/3 for the Universe.     

Study of Tachyon Warm Intermediate and Logamediate Inflationary Universe from Loop Quantum Cosmological Perspective

We have studied the tachyon intermediate and logamediate warm inflation in loop quantum cosmological background by taking the dissipative co-efficient Γ=Γ₀ (where Γ₀ is a constant) in “intermediate” inflation and Γ=V(φ), (where V(φ) is the potential of tachyonic field) in “logamediate” inflation. We have assumed slow-roll condition to construct scalar field φ, potential V, N-folds, etc. Various slow-roll parameters have also been obtained. We have analyzed the stability of this model through graphical representations.     

Axially Symmetric Inflationary Universe in General Relativity

We have investigated a simple axially symmetric inflationary universe in the presence of mass less scalar field with a flat potential. To get an inflationary universe, we have considered a flat region in which potential V is constant. Some physical properties of the universe are also discussed.     

Spin Zero Quantum Relativistic Particles in Einstein Universe

We find exact eigenvalues and eigenfunctions of relativistic massless scalar particle conformally coupled to a background Einstein universe.     

New Solutions to Einstein's Equations in the Taub Universe and Their Accelerating Stage

Following a specific strategy in which the cosmological time variables are operated upon, a new family of solutions to the empty Taub universe is found. Among the characteristics of such a family, it stands the positive acceleration provided by the tri-curvature property of this universe to two of the three scale factors of the Taub model. This effect of the tri-curvature results not in a restoring force such as normal gravity but in the conversion of the Taub cosmology into an accelerating universe.     

Tachyon field in cosmology

We study cosmological effects of homogeneous tachyon field as dark energy. We concentrate on two different scalar field potentials, the inverse square potential and the exponential potential. These models have a unique feature that the matter density parameter and the density parameter for tachyons remain comparable for a large range in red-shift. It is shown that there exists a range of parameters for which the universe undergoes an accelerated expansion and the evolution is consistent with structure formation requirements. For a viable model we require fine tuning of parameters comparable to that in ACDM or in quintessence models. For the exponential potential, the accelerated phase is followed by a phase witha(t) α t ^2/3 thus eliminating a future horizon.     

Bianchi Type-V Inflationary Universe in General Relativity

A Bianchi type-V space-time is considered in the presence of massless scalar field with a flat potential. To get an inflationary universe, we have considered a flat region in which potential V is constant. Some physical and kinematical properties of the model are also discussed.     

First Principles Calculation of the Baryon Asymmetry of the Universe: Generalities and Application

We present a formalism that allows the computation of the lepton asymmetry of the universe from first principles of statistical physics and quantum field theory (this lepton asymmetry is then converted to a baryon asymmetry via sphaleron processes). This formalism includes a thermal bath of Standard Model particles (active neutrinos) coupled to a new sector that is out-of-equilibrium (sterile neutrinos). The key point that allows a first principles computation is that the number of sterile neutrinos produced during the relevant cosmological period remains small (we assume zero sterile neutrinos initially). In such a case, it is possible to expand the formal solution of Liouville's equation perturbatively and obtain a master formula for the lepton asymmetry expressed in terms of non-equilibrium Wightman functions. The master formula neatly separates CP-violating contributions from finite temperature correlation functions and satisfies all three Sakharov conditions. These correlation functions can then be evaluated perturbatively; the validity of the perturbative expansion depends on the parameters of the model considered. Here we choose the νMSM (i.e. a minimal extension of the Standard Model that includes three generations of sterile neutrinos with masses of the order of the electroweak scale) to illustrate the use of the formalism, but it could in principle be applied to other models.     

Moving Observers in an Isotropic Universe

This paper considers how the motion of an observer in an isotropic universe may be determined by measurements. This provides a means to identify inertial frames, yielding a simple resolution to the twins paradox of relativity theory in such a universe. We propose that isotropy is a requirement for a frame to be inertial; this makes it possible to relate motion to the large scale structure of the universe.     

A Higher Dimensional Inflationary Universe in General Relativity

A five dimensional Kaluza-Klein inflationary universe is investigated in the presence of massless scalar field with a flat potential. To get an inflationary universe a flat region in which potential V is constant is considered. Some physical and kinematical properties of the universe are also discussed.     

Isotropic Evolution of a JBD Anisotropic Bianchi Universe

I study the dynamical effects due to the Brans-Dicke scalar -field at the early stages of a supposedly anisotropic Universe expansion in the scalar-tensor cosmology of Jordan-Brans-Dicke. This is done considering the behaviour of the general solutions for the homogeneous model of Bianchi type VII in the vacuum case. I conclude that the Bianchi-VII₀ model shows an isotropic expansion and that its only physical solution is equivalent to a Friedman-Robertson-Walker spacetime whose evolution can, depending on the value of the JBD coupling constant, begin in a singularity and, after expanding (inflating, if > 0), shrink to another, or starting in a non-singular state, collapse to a singularity. I also conclude that the general Bianchi-VII _h (with h 0) models show strong curvature singularities producing a complete collapse of the homogeneity surfaces to 2D-manifolds, to 1D-manifolds or to single points. Our analysis depends crucially on the introduction of the so-called intrinsic time, , as the product of the JBD scalar field times a mean scale factor a ³ = a ₁ a ₂ a ₃, in which the finite-cosmological-time evolution of this universe unfolds into an infinite -range. These universes isotropize from an anisotropic initial state, thence I conclude that they are stable against anisotropic perturbations.     

Does Operator Ordering Need Wormhole Dominance in the Wavefunction of the Universe?

In dealing with the wavefunction of the universe there is a debate on the various proposals about the boundary condition of the wavefunction of the universe. At present we have three proposals, namely, the Hartle-Hawking proposal, the tunneling proposal and the Linde proposal. Recently it has been argued that the operator ambiguity factor has a decisive role in deciding the consequences of the various wavefunction at the zero scale factor region. In the present paper we discuss the role of operator ordering in the light of wormhole dominance proposal proposed by one of the authors and compare the results with that of others obtained earlier. We present an interpretation of operator ordering as a contribution of some sort of matter fields and discuss the role of complex path WKB analysis in avoiding the initial singularity and allowing us to incorporate the contribution of wormhole in the wavefunction of the universe.     

大数猜想与暗物质

讨论恒星质量、核子质量、暗物质粒子质量和普朗克质量四者间通过大数A～10¹⁹联系在一起,而且强相互作用与引力间也唯象地通过大数A似乎有着某种深层的联系.     

Rotationally Symmetric Massless Modes in Closed Robertson-Walker Universe

The aim of the present paper is to investigate the minimally coupled rotationally symmetric scalar field configurations in spatially closed Friedman-Robertson-Walker Universe with incoherent dust. We have got the closed form solution of the Klein-Gordon equation in terms of two real-valued linearly independent hypergeometric functions. The orthonormal set of positive-frequency-like parity modes thereafter derived points out that each parity given state is conformally built up of three Einsteinian particle states and also leads to the explicit coordinate-representation of the field propagator.     

曲面相机阵列多分辨成像方法

针对现有成像系统因数据冗余而无法兼顾大视场、高分辨、高效性的问题,结合人眼视网膜变分辨成像和并列式复眼成像原理,设计一种多分辨率成像的复合仿生成像系统.该成像系统按照球面和平面兼顾的曲面布局方式,利用11个相机镜头构建相机阵列,组成了四个等级分辨率的子眼拍摄模块.通过物距100 m的远景实验和物距10 m的近景实验发现,该系统在实现高分辨成像的同时,获得总视场达150.8°×37.8°.多分辨率成像实验结果表明,该系统获取的图像的分辨率从中心视场到边缘视场逐渐降低,并且相较于中心清晰全视场成像,四级分辨率成像的拼接图像数据量减少了17.2倍的数据冗余.     

Energy Momentum of Marder Universe in Teleparallel Gravity

In order to evaluate the energy distribution (due to matter and fields including gravitation) associated with a space-time model of cylindrically-symmetric Marder universe, we consider the Møller, Einstein, Bergmann–Thomson and Landau–Lifshitz energy and momentum definitions in the teleparallel gravity (TG). The energy-momentum distributions are found to be zero. These results are the same as a previous works of Aygün et al., they investigated the same problem in general relativity (GR) by using the Einstein, Møller, Bergmann–Thomson, Landau–Lifshitz (LL), Papapetrou, Qadir–Sharif and Weinberg’s definitions. These results support the viewpoints of Banerjee–Sen, Xulu, Radinschi and Aydo?du–Salt?. Another point is that our study agree with previous works of Cooperstock–Israelit, Rosen, Johri et al. This paper indicates an important point that these energy-momentum definitions agree with each other not only in general relativity but also in teleparallel gravity. It is also independent of the teleparallel dimensionless coupling constants, which means that it is valid not only in the teleparallel equivalent of general relativity, but also in any teleparallel model.