Cosmological Constant and Stability of the Cosmological Models

The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters and were discussed respectively. Near , the cosmological model is unstable with the change of , and near , the cosmological model is unstable with the change of . So when we consider the stable cosmological model, we must consider the nonzero cosmological constant.

The Precise Inner Solutions of Gravity Field Equations of Hollow and Solid Spheres and the Theorem of Singularity

The precise inner solutions of gravity field equations of hollow and solid spheres are calculated in this paper. To avoid space curvature infinite at the center of solid sphere, we set an integral constant to be zero directly at present. However, according to the theory of differential equation, the integral constant should be determined by the known boundary conditions of spherical surface, in stead of the metric at the spherical center. By considering that fact that the volumes of three dimensional hollow and solid spheres in curved space are different from that in flat space, the integral constants are proved to be nonzero. The results indicate that no matter what the masses and densities of hollow sphere and solid sphere are, there exist space-time singularities at the centers of hollow sphere and solid spheres. Meanwhile, the intensity of pressure at the center point of solid sphere can not be infinite. That is to say, the material can not collapse towards the center of so-called black hole. At the center and its neighboring region of solid sphere, pressure intensities become negative values. There may be a region for hollow sphere in which pressure intensities may become negative values too. The common hollow and solid spheres in daily live can not have such impenetrable characteristics. The results only indicate that the singularity black holes predicated by general relativity are caused by the descriptive method of curved space-time actually. If black holes exist really in the universe, they can only be the Newtonian black holes, not the Einstein’s black holes. The results revealed in the paper are consistent with the Hawking theorem of singularity actually. They can be considered as the practical examples of the theorem.

Anisotropic Standard Decelerating Cosmological Model with Quadratic Equation of State

Spatially homogeneous and anisotropic Bianchi type-I cosmological model containing perfect fluid with quadratic equation of state has been diagnosed in general theory of relativity. To obtain a deterministic solution, we have used a relation between metric potentials. The exact solution of Einstein’s field equations thus obtained represents an expanding and decelerating universe. The physical and kinematical parameters of the model have also been analyzed with certain constrained between the parameters of the quadratic equation of state.

Relativity: Towards a New Interpretation

The aim of this paper essentially lies in attributing a new meaning, coherent with phenomenological reality, to several phenomena usually classified as relativistic, such as the alleged increase of the mean lifetime of muons and the gravitational redshift. According to the model herein proposed, all the relativistic equations preserve their validity, albeit with a different connotation. We consider a Simple-Harmonically Oscillating Universe, characterized by a null curvature parameter, postulating the existence of a further spatial dimension, not directly perceivable. Time is considered as being absolute, although instruments and devices of whatever kind, commonly employed to measure it, may be significantly influenced by motion and gravity. The Planck Constant is regarded as a parameter, locally variable and subjected to a cyclic evolution. Time and space are treated as quantized physical quantities.

Why the Big Bang Model Cannot Describe the Observed Universe Having Pressure and Radiation

It has been recently shown that, since in general relativity (GR), given one time label t, one can choose any other time label t → t*= f(t), the pressure of a homogeneous and isotropic fluid is intrinsically zero (Mitra, Astrophys. Sp. Sc. 333, 351, 2011). Here we explore the physical reasons for the inevitability of this mathematical result. The essential reason is that the Weyl Postulate assumes that the test particles in a homogeneous and isotropic spacetime undergo pure geodesic motion without any collisions amongst themselves. Such an assumed absence of collisions corresponds to the absence of any intrinsic pressure. Accordingly, the “Big Bang Model” (BBM) which assumes that the cosmic fluid is not only continuous but also homogeneous and isotropic intrinsically corresponds to zero pressure and hence zero temperature. It can be seen that this result also follows from the relevant general relativistic first law of thermodynamics (Mitra, Found. Phys. 41, 1454, 2011). Therefore, the ideal BBM cannot describe the physical universe having pressure, temperature and radiation. Consequently, the physical universe may comprise matter distributed in discrete non-continuous lumpy fashion (as observed) rather than in the form of a homogeneous continuous fluid. The intrinsic absence of pressure in the “Big Bang Model” also rules out the concept of a “Dark Energy”.

一类无奇点宇宙模型

按照Penrose-Hawking的奇点定理,在场源物质无旋、无加速且能量密度满足条件ρ+3p≥0的宇宙模型中一定存在奇点.本文研究了场源物质有旋时的无奇点宇宙模型,获得了几种无奇点的宇宙解.