SPIN-ROTATION COUPLING EFFECTS ON THE STRUCTURE FORMATION IN GÖDEL UNIVERSE AND COBE DATA

2002 ◽  
Vol 11 (05) ◽  
pp. 733-737
Author(s):  
L. C. GARCIA DE ANDRADE
Keyword(s):  
Structure Formation ◽  
Fluid Model ◽  
Temperature Fluctuations ◽  
Constant Term ◽  
Spin Rotation ◽  
Cosmological Perturbation ◽  
Cartan Torsion ◽  
Rotating Universe ◽  
The Universe ◽  
Gödel Universe

A rotating universe represented by the Gödel metric in spacetimes with Cartan torsion is investigated. The spin–torsion coupling is shown to contribute to the structure formation in an apppreciable way only at the early stages of the universe. To demonstrate these conjectures, we have made use of a spinning fluid model in Einstein–Cartan gravity. We also show that autoparallel equation in Riemann–Cartan spacetime leads to the evolution equation of the cosmological perturbation where the spin-rotation coupling contributes to the growth of inhomogeneities through a constant term. From this idea, one is able to estimate that torsion in the Planck era is around 1015 s -1 where COBE constraint on temperature fluctuations is used in this computation. A spin density of the universe of 1053 g · cm -1 s -1 is also obtained in our framework.

scholarly journals Time Varying Cosmological Constant and Its Implications for Structure Formation

2021 ◽  
Author(s):  
Louise Rebecca ◽  
C Sivaram ◽  
Arun Kenath
Keyword(s):  
Cosmological Constant ◽  
Structure Formation ◽  
Large Scale ◽  
Constant Term ◽  
Time Varying ◽  
True Nature ◽  
Large Scale Structures ◽  
Set Constraints ◽  
Scale Structures ◽  
The Universe

Although the presence of dark energy is well established from various observations, its true nature is still not well understood. The cosmological constant term seems to be the preferred candidate. In earlier work we had a constant cosmological constant term to limit the sizes of large-scale structures at lower redshifts. In this work, we extend this to large scale structures at higher redshifts. Here we invoke a time varying cosmological constant to set constraints on sizes of galaxies at high redshifts and see that they are consistent with their observed sizes. The time-varying cosmological constant also provides a possible solution to the puzzle of structure formation of large disk galaxies (like the Wolfe disk) observed at very early stages of the Universe. Future observations of galaxies at even higher redshifts could support our approach.

scholarly journals Supercomputer simulations of structure formation in the Universe

2016 ◽  
Vol 12 (S325) ◽  
pp. 10-16
Author(s):  
Tomoaki Ishiyama
Keyword(s):  
Domain Decomposition ◽  
Structure Formation ◽  
Short Range ◽  
Large Scale ◽  
Massively Parallel ◽  
Average Performance ◽  
And Performance ◽  
Performance Results ◽  
The Universe ◽  
Peak Speed

AbstractWe describe the implementation and performance results of our massively parallel MPI†/OpenMP‡ hybrid TreePM code for large-scale cosmological N-body simulations. For domain decomposition, a recursive multi-section algorithm is used and the size of domains are automatically set so that the total calculation time is the same for all processes. We developed a highly-tuned gravity kernel for short-range forces, and a novel communication algorithm for long-range forces. For two trillion particles benchmark simulation, the average performance on the fullsystem of K computer (82,944 nodes, the total number of core is 663,552) is 5.8 Pflops, which corresponds to 55% of the peak speed.

On structure formation in the universe

1994 ◽  
Vol 222 (1-2) ◽  
pp. 205-212
Author(s):  
A. Satya Narayanan
Keyword(s):  
Structure Formation ◽  
The Universe

scholarly journals Dissipative unified dark fluid model

2019 ◽  
Vol 28 (09) ◽  
pp. 1950110
Author(s):  
Esraa Elkhateeb
Keyword(s):  
Dark Energy ◽  
Fluid Model ◽  
Dynamical Behavior ◽  
Power Laws ◽  
Viscosity Coefficient ◽  
Distance Modulus ◽  
Effective Equation ◽  
Dark Fluid ◽  
System Solution ◽  
The Universe

We consider a unified barotropic dark fluid model with dissipation. Our fluid asymptotes between two power laws and so can interpolate between the dust and dark energy (DE) equations-of-state at early and late times. The dissipative part is a bulk viscous part with constant viscosity coefficient. The model is analyzed using the phase-space methodology which helps to understand the dynamical behavior of the model in a robust manner without reference to the system solution. The parameters of the model are constrained through many observational constraints. The model is tested through many physical and observational tests. We first considered the model independent [Formula: see text] test. Results for [Formula: see text] are plotted against the BAO data for this quantity from different authors, which shows that the model is consistent with the data points for the full redshift range. The [Formula: see text] statistics results in the value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. The Hubble parameter equation is solved numerically and results are plotted against the recent set of Hubble data. The [Formula: see text] test with the Hubble data resulted in the [Formula: see text] value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. The distance modulus at different values of redshift is calculated numerically and results are compared to the newest set of SNe Ia data, the Pantheon Sample. We obtained a [Formula: see text] value of [Formula: see text] with a [Formula: see text]-value of [Formula: see text]. These results show that our model is efficiently consistent with observations. The model expectations for the evolution of the universe are also studied by testing the evolution of the deceleration parameter, the density of the universe, and the effective equation-of-state parameter of the model and of its underlying dark energy candidate. The value of the present day viscosity coefficient of the cosmic fluid, [Formula: see text], is estimated. It is found to be [Formula: see text][Formula: see text]Pa[Formula: see text]s. We argue that this model is able to explain the behavior of the universe evolution.

scholarly journals Structure Constraints from Large Angle CMB Anisotropies

1992 ◽  
Vol 9 ◽  
pp. 319-321
Author(s):  
J. Richard Bond
Keyword(s):  
Correlation Function ◽  
Structure Formation ◽  
Large Distance ◽  
Large Angle ◽  
Microwave Background ◽  
Scale Invariant ◽  
Intermediate Angle ◽  
History Of ◽  
Adiabatic Fluctuations ◽  
The Universe

Constraints on models of cosmic structure formation that can be drawn from current limits on large angle microwave background anisotropies are now competitive with those from recent small and intermediate angle experiments and are relatively insensitive to the reheating history of the Universe. Here I give limits on Gaussian scale invariant adiabatic fluctuations and describe the role that the large angle results play in constraining models with enhanced large distance galaxy clustering power inferred from correlation function measurements is described.

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