scholarly journals ISOTROPIZATION IN CHAPLYGIN MATTER UNIVERSES CONNECTED BY A WORMHOLE

2013 ◽  
Vol 22 (10) ◽  
pp. 1350067 ◽  
Author(s):  
ANNA MOKEEVA ◽  
VLADIMIR POPOV
Keyword(s):  
Cosmological Model ◽  
Late Stage ◽  
Initial Singularity ◽  
Accelerated Expansion ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Classical Level ◽  
Anisotropic Matter ◽  
Symmetric Region

Chaplygin anisotropic matter governing the cosmological evolution in two identical universes with an intermediate static spherically symmetric region is considered. The static region contains a wormhole allowing one to pass between two horizons. The metric in the nonstatic region represents a kind of an anisotropic Kantowski–Sachs cosmological model starting from a horizon instead of the initial singularity. A classification of the cosmologies with a monotonic late stage is presented. It is shown that only one scenario can involve a de Sitter regime. The scales in the de Sitter phase allows one to describe the earliest accelerated expansion on the classical level.

scholarly journals The Asymmetric Cosmic Time – The Key to a New Cosmological Model

2020 ◽  
Vol 2 (1) ◽  
pp. 97-111
Author(s):  
Horst Fritsch ◽  
Eberhard Schluecker
Keyword(s):  
Cosmological Model ◽  
Initial Conditions ◽  
Logical Consequence ◽  
Cosmic Time ◽  
Big Bang ◽  
Relativity Theory ◽  
Accelerated Expansion ◽  
Theory Of Relativity ◽  
De Sitter ◽  
The Universe

The asymmetric cosmic time is a logical consequence of the General Theory of Relativity (GR), if one demands that it should apply to the entire cosmos. From the simplest cosmological model that is consistent with the ART (Einstein-de Sitter model) thus follows the < Cosmic Time Hypothesis > (CTH), which offers solutions for many unsolved problems of cosmology that the current standard model of cosmology (ɅCDM model) cannot explain. According to the CTH, space, time and matter form a unit and develop evolutionarily according to identical, time-dependent laws. According to the CTH time has neither beginning nor end. The "big bang" disappears into the infinite past, which is why the universe manages without inflation. The accelerated expansion of the universe is also unlikely to occur if the SN-Ia measurement results are interpreted using the CTH. The cosmological constant Ʌ can then be omitted (Ʌ=0) and consequently no "dark energy" is needed. In addition, the CTH also provides interesting results on the topics: Initial conditions for hypotheses, stability of the expanding, flat universe (Ω=1), cosmic energy balance (is there negative energy ?), theory of earth expansion, unification of natural forces, Mach's principle. Should the CTH receive broad experimental confirmation, the GR could be extended to the "Universal Relativity Theory" (UR).

Tissue microarray based classification of early and late stage colorectal cancer in optical and virtual microscopy

2007 ◽  
Vol 45 (05) ◽  
Author(s):  
F Sipos ◽  
S Spisák ◽  
T Krenács ◽  
O Galamb ◽  
B Galamb ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Tissue Microarray ◽  
Late Stage ◽  
Virtual Microscopy

Cosmological spacetimes

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Cosmological Model ◽  
Large Scale ◽  
Cosmic Time ◽  
De Sitter ◽  
Matter Distribution ◽  
Observable Universe ◽  
Cosmological Principle ◽  
Riemannian Spacetime ◽  
The Universe ◽  
Copernican Principle

This chapter provides a few examples of representations of the universe on a large scale—a first step in constructing a cosmological model. It first discusses the Copernican principle, which is an approximation/hypothesis about the matter distribution in the observable universe. The chapter then turns to the cosmological principle—a hypothesis about the geometry of the Riemannian spacetime representing the universe, which is assumed to be foliated by 3-spaces labeled by a cosmic time t which are homogeneous and isotropic, that is, ‘maximally symmetric’. After a discussion on maximally symmetric space, this chapter considers spacetimes with homogenous and isotropic sections. Finally, this chapter discusses Milne and de Sitter spacetimes.

Classification of Static Spherically Symmetric Spacetimes by Noether Symmetries

2013 ◽  
Vol 52 (10) ◽  
pp. 3534-3542 ◽  
Author(s):  
Ashfaque H. Bokhari ◽  
A. G. Johnpillai ◽  
A. H. Kara ◽  
F. M. Mahomed ◽  
F. D. Zaman
Keyword(s):  
Spherically Symmetric ◽  
Noether Symmetries ◽  
Symmetric Spacetimes ◽  
Spherically Symmetric Spacetimes ◽  
Static Spherically Symmetric Spacetimes

The classification of spherically symmetric space-times

1995 ◽  
Vol 110 (3) ◽  
pp. 317-334 ◽  
Author(s):  
A. Qadir ◽  
M. Ziad
Keyword(s):  
Symmetric Space ◽  
Spherically Symmetric

scholarly journals LUKEWARM BLACK HOLES IN QUADRATIC GRAVITY

2011 ◽  
Vol 26 (14) ◽  
pp. 999-1007 ◽  
Author(s):  
JERZY MATYJASEK ◽  
KATARZYNA ZWIERZCHOWSKA
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Fourth Order ◽  
Spherically Symmetric ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Quadratic Gravity ◽  
De Sitter Universe ◽  
Electrically Charged

Perturbative solutions to the fourth-order gravity describing spherically-symmetric, static and electrically charged black hole in an asymptotically de Sitter universe is constructed and discussed. Special emphasis is put on the lukewarm configurations, in which the temperature of the event horizon equals the temperature of the cosmological horizon.

Charged gravastars in f(R,T,RμνTμν) gravity

2021 ◽  
pp. 2150084
Author(s):  
Z. Yousaf ◽  
M. Z. Bhatti
Keyword(s):  
Perfect Fluid ◽  
Energy Momentum Tensor ◽  
Equations Of State ◽  
Mathematical Formulation ◽  
Momentum Tensor ◽  
Spherically Symmetric ◽  
De Sitter ◽  
The Stability ◽  
Physical Features ◽  
Modified Theory

We explore the aspects of the electromagnetism on the stability of gravastar in a particular modified theory, i.e. [Formula: see text] where [Formula: see text], [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of energy–momentum tensor. We assume a spherically symmetric static metric coupled comprising of perfect fluid in the presence of electric charge. The purpose of this paper is to extend the results of [S. Ghosh, F. Rahaman, B. K. Guha and S. Ray, Phys. Lett. B 767 (2017) 380.] to highlight the effects of [Formula: see text] gravity in the formation of charged gravastars. We demonstrated the mathematical formulation, utilizing different equations of state, for the three respective regions (i.e. inner, shell, exterior) of the gravastar. We have matched smoothly the interior de Sitter and the exterior Reissner–Nordström metric at the hypersurface. At the end we extracted few conclusions by working on the physical features of the charged gravastar, mathematically and graphically.

Stability of generalized polytropic models

2019 ◽  
Vol 16 (04) ◽  
pp. 1950056
Author(s):  
I. Nazir ◽  
M. Azam
Keyword(s):  
Equation Of State ◽  
Local Density ◽  
Hydrostatic Equilibrium ◽  
Physical Parameters ◽  
Spherically Symmetric ◽  
Anisotropic Matter ◽  
Polytropic Equation ◽  
Density Perturbations ◽  
Radial Forces ◽  
The Stability

In this paper, we have investigated the stability of a spherically symmetric object with charged anisotropic matter by using the concept of cracking. The cracking is a very intuitive technique to check the stability which is based on the analysis of the radial forces that appear on the system due to perturbations taking it out of its equilibrium state. For this, we have applied and studied the effect of local density perturbations to the hydrostatic equilibrium equation and on all the physical parameters with generalized polytropic equation of state. It is found that some of the generalized polytropic models exhibit cracking.

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