Dark matter and the formation of large-scale structure in the Universe

A new scenario of clustering in a two component dark matter universe is discussed, from which we would expect the difference between the distributions of quasars and galaxies on the scale of 10–100 Mpc and the difference between the distributions of quasars withZ>2 andZ<2. Several analyses on quasars distribution are in good agreement with these predictions.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Energy conditions and inhomogeneities in the Universe

The so-called dominant energy condition and the strong energy condition (of singularity theorems) cannot be violated by the negative effective ‘pressure’ arising from the inhomogeneous distribution of matter in the Universe.     

Dark energy,antimatter gravity and geometry of the Universe

In this paper, motivated by fermions tunneling method of 4 dimensional black holes, we extend the analysis to the charged Kerr black hole in five dimension by constructing a set of appropriate matrices γ ^μ for general covariant Dirac equation. As a result, we successfully recover the expected Hawking temperature.     

Dark matter and dark energy in the Universe: Astrophysical reasons and theoretical models

The general review on the problem of dark matter and dark energy in observable Universe is given. The problem is treated from the point of view of research fields on the boundary of which this fundamental task is situated, namely, the astrophysics and theoretical physics. We emphasize that interdisciplinary nature of “dark sector” of Universe problem can assist in its resolution. The paper does not describe the history of the question, but is centred on revealing the main trends and perspectives. Published in Ukrainian in Kinematika i Fizika Nebesnykh Tel, 2009, Vol. 25, No. 2, pp. 83–106. The article was translated by the authors.     

Energy Composition of the Universe: Time-Independent Internal Symmetry

The energy composition of the Universe, as emerged from the Type Ia supernova observations and the WMAP data, looks preposterously complex, – but only at the first glance. In fact, its structure proves to be simple and regular. An analysis in terms of the Friedmann integral enables to recognize a remarkably simple time-independent covariant robust recipe of the cosmic mix: the numerical values of the Friedmann integral for vacuum, dark matter, baryons and radiation are approximately identical. The identity may be treated as a symmetry relation that unifies cosmic energies into a regular set, a quartet, with the Friedmann integral as its common genuine time-independent physical parameter. Such cosmic internal (non-geometrical) symmetry exists whenever cosmic energies themselves exist in nature. It is most natural for a finite Universe suggested by the WMAP data. A link to fundamental theory may be found under the assumption about a special significance of the electroweak energy scale in both particle physics and cosmology. A freeze-out model developed on this basis demonstrates that the physical nature of new symmetry might be due to the interplay between electroweak physics and gravity at the cosmic age of a few picoseconds. The big ‘hierarchy number’ of particle physics represents the interplay in the model. This number quantifies the Friedmann integral and gives also a measure to some other basic cosmological figures and phenomena associated with new symmetry. In this way, cosmic internal symmetry provides a common ground for better understanding of old and recent problems that otherwise seem unrelated; the coincidence of the observed cosmic densities, the flatness of the co-moving space, the initial perturbations and their amplitude, the cosmic entropy are among them.     

Simulation of a ground-layer adaptive optics system for the Kunlun Dark Universe Survey Telescope

Ground Layer Adaptive Optics (GLAO) is a recently developed technique extensively applied to ground-based telescopes, which mainly compensates for the wavefront errors induced by ground-layer turbulence to get an appropriate point spread function in a wide field of view. The compensation results mainly depend on the turbulence distribution. The atmospheric turbulence at Dome A in the Antarctic is mainly distributed below 15 meters, which is an ideal site for applications of GLAO. The GLAO system has been simulated for the Kunlun Dark Universe Survey Telescope, which will be set up at Dome A, and uses a rotating mirror to generate several laser guide stars and a wavefront sensor with a wide field of view to sequentially measure the wavefronts from different laser guide stars. The system is simulated on a computer and parameters of the system are given, which provide detailed information about the design of a practical GLAO system.     

暗能量的理论模型

自1998年超新星观测发现宇宙加速膨胀以来,暗能量问题已经成为当前天体物理和宇宙学研究中最重要的问题之一.此后关于宇宙微波背景辐射和大尺度结构的测量也进一步支持了1998年的发现.该文首先概述了宇宙学的起源,然后详细介绍了目前解释宇宙加速膨胀机制的三类模型,包括各模型提出的动机、存在的优缺点,以及当前的主要进展等.最后对暗能量模型作了总结和展望.     

Probing Dark Energy with Supernova Searches

Four years ago, two teams presented independent analyzes coming from photometry of type Ia supernovae at various distances. The results presented back then shook-up the scientific community: the universe is accelerating with a positive repulsive fluid sometimes called dark energy. No significant work has disproved the fundamental results, yet some doubt subsists in the assumptions behind the full use of type Ia supernovae as perfect distance indicators. The uncertainty of the evolution problem, the explosion mechanisms and the diversity of the observed light curves properties are often cited problems. All these aspects are now being deeply investigated in to-come or already started supernova searches along with the on-going quest of determining the nature of dark energy. We will present here a brief introduction to the use of type Ia supernova in cosmology, the current status of supernova cosmology as well as an overview of the wide supernova surveys about to begin.     

Energy enigmas in the early Universe and related problems in Newtonian cosmology

Some paradoxical situations regarding the balance between the different forms of energy present and the velocities of expansion in the early stages of the big bang are discussed. Solutions are suggested in the framework of Newtonian gravitation.     

Constraints on Dark Energy from the CSST Galaxy Clusters

We study the potential of the galaxy cluster sample expected from the Chinese Space Station Telescope(CSST)survey to constrain dark energy properties.By modeling the distribution of observed cluster mass for a given true mass to be log-normal and adopting a selection threshold in the observed mass M_200m≥0.836×10¹⁴ h^-1 M_⊙,we find about 4.1×10⁵ clusters in the redshift range 0≤z≤1.5 can be detected by the CSST.We construct the Fisher matrix fo...     

An Interacting Model of Dark Energy in Brans-Dicke Theory

In this paper it is shown that in non-minimally coupled Brans-Dicke theory containing a self-interacting potential, a suitable conformal transformation can automatically give rise to an interaction between the normal matter and the Brans-Dicke scalar field. Considering the scalar field in the Einstein frame as the quintessence matter, it has been shown that such a non-minimal coupling between the matter and the scalar field can give rise to a late time accelerated expansion for the universe preceded by a decelerated expansion for very high values of the Brans-Dicke parameter ω. We have also studied the observational constraints on the model parameters considering the Hubble and Supernova data.     

A Better Reconciliation of Hubble Tension in the Dark Energy Scalar Field

Hubble tension between the local measurement and global observation has been a key problem in cosmology. In this paper, we consider the quintessence scalar field, phantom field and quintom field as the dark energy to reconcile this problem. Different from most previous work, we start from the dimensionless equation of state(w) of dark energy, not a parameterization of potential. The combined analysis shows that observational data sets favor Hubble constant H₀ =71.3_-0.917     

Dynamics of Kantowski-Sachs universe with magnetized anisotropic Dark Energy

Kantowski-Sachs cosmological model in the presence of magnetized anisotropic dark energy is investigated. The energy-momentum tensor consists of anisotropic fluid with anisotropic EoS p=ωρ and a uniform magnetic field of energy density ρ _B . We obtain exact solutions to the field equations using the condition that expansion is proportional to the shear scalar. The physical behavior of the model is discussed with and without magnetic field. We conclude that universe model as well as anisotropic fluid does not approach isotropy through the evolution of the universe.     

Holographic Dark Energy Cosmological Models in f(G) Theory

In this paper, Locally Rotationally Symmetric (LRS) Bianchi type-I models with holographic dark energy within the framework of f(G) theory of gravitation are thought about. So as to get determinate solutions, volumetric exponential expansion, power law expansion and hybrid expansion law are mentioned. The physical interpretations of the solution have been studied by using some physical quantizes. Additionally to make the interpretation more clear for that the statefinder diagnostic pair {r, s} and jerk parameter are analyzed to characterize completely different phases of the universe.     

Reconstruction of f(T) gravity from the Holographic Dark Energy

Among different candidates to play the role of Dark Energy (DE), modified gravity has emerged as offering a possible unification of Dark Matter (DM) and DE. The purpose of this work is to develop a reconstruction scheme for the modified gravity with f(T) action using holographic energy density. In the framework of the said modified gravity we have considered the equation of state of the Holographic DE (HDE) density. Subsequently we have developed a reconstruction scheme for modified gravity with f(T) action. Finally we have obtained a modified gravity action consistent with the HDE scenario.     

The Feasibility of Constraining Dark Energy Using LAMOST Redshift Survey

We consider using future redshift surveys with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to constrain the equation of state of dark energy ω. We analyze the Alcock & Paczyriski (AP) effect imprinted on the two-point correlation function of galaxies in redshift space. The Fisher matrix analysis is applied to estimate the expected error bounds of ω0 and ωa from galaxy redshift surveys, ω0 and ωa being the two parameters in the equation of state parametrization ω(z) = ω0 + ωaz/(1 + z). Strong degeneracies between ω0 and ωa are found. The direction of the degeneracy in ω0 - ωa plane, however, rotates counter-clockwise as the redshift increases. LAMOST can potentially contribute in the redshift range up to 0.5. In combination with other high redshift surveys, such as the proposed Kilo-Aperture Optical Spectrograph project (KAOS), the joint constraint derived from galaxy surveys at different redshift ranges is likely to efficiently break the degeneracy of ω0 and ωa. We do not anticipate that the nature of dark energy can be well constrained with LAMOST alone, but it may help to reduce the error bounds expected from other observations, such as the Supernova/Acceleration Probe (SNAP).