scholarly journals Isotropization of Homogeneous Cosmological Models

1974 ◽  
Vol 63 ◽  
pp. 273-282
Author(s):  
I. D. Novikov
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Cosmological Models ◽  
Matter Distribution ◽  
Cosmological Singularity ◽  
Universe Expand ◽  
Starting Point ◽  
Microwave Background Radiation ◽  
Friedmann Cosmological Models ◽  
The Universe

Observations primarily of the microwave background radiation show that the Universe expands isotropically with a high degree of accuracy at the present time and that the matter distribution is homogeneous on a large scale. Thus, the Friedmann cosmological models are a good approximation today for the expanding Universe. This is valid for at least some period of time in the past too. But how did the Universe expand and what was the matter distribution close to the starting point, near the cosmological singularity?

The TopHat Cosmic Microwave Background Anisotropy Experiment

2005 ◽  
Vol 201 ◽  
pp. 65-70
Author(s):  
Robert F. Silverberg ◽  
Keyword(s):  
Cosmic Microwave Background ◽  
Large Scale ◽  
Background Radiation ◽  
High Sensitivity ◽  
Microwave Background ◽  
Long Duration ◽  
Cosmic Microwave Background Anisotropy ◽  
Microwave Background Radiation ◽  
The Universe ◽  
Large Scale Structure Formation

We have developed a balloon-borne experiment to measure the Cosmic Microwave Background Radiation anisotropy on angular scales from ˜50° down to ˜20′. The instrument observes at frequencies between 150 and 690 GHz and will be flown on an Antarctic circumpolar long duration flight. To greatly improve the experiment performance, the front-end of the experiment is mounted on the top of the balloon. With high sensitivity, broad sky coverage, and well-characterized systematic errors, the results of this experiment can be used to strongly constrain cosmological models and probe the early stages of large-scale structure formation in the Universe.

scholarly journals Large Scale Anisotropy of the Cosmic Microwave Background

1974 ◽  
Vol 63 ◽  
pp. 157-162 ◽  
Author(s):  
R. B. Partridge
Keyword(s):  
Angular Distribution ◽  
Large Scale ◽  
Background Radiation ◽  
Big Bang ◽  
Microwave Background ◽  
Initial State ◽  
Microwave Background Radiation ◽  
Cosmological Data ◽  
The Big Bang ◽  
The Universe

It is now generally accepted that the microwave background radiation, discovered in 1965 (Penzias and Wilson, 1965; Dicke et al., 1965), is cosmological in origin. Measurements of the spectrum of the radiation, discussed earlier in this volume by Blair, are consistent with the idea that the radiation is in fact a relic of a hot, dense, initial state of the Universe – the Big Bang. If the radiation is cosmological, measurements of both its spectrum and its angular distribution are capable of providing important – and remarkably precise – cosmological data.

scholarly journals Large-Scale Anisotropy of the Cosmic Relic Radiation in Spatially Open Cosmological Models

1983 ◽  
Vol 104 ◽  
pp. 149-152
Author(s):  
V. N. Lukash
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Microwave Background ◽  
Spatial Homogeneity ◽  
Sensitive Tool ◽  
Microwave Background Radiation ◽  
Universal Expansion ◽  
Celestial Sphere ◽  
The Universe ◽  
Small Anisotropy

The observed microwave background radiation is a sensitive tool for studying the fundamental features of the universe. A puzzling constancy on the celestial sphere of the temperature, T, of the equilibrium relic radiation coming to us from causally nonrelated regions of space-time points to the global spatial homogeneity and isotropy of the cosmological expansion. On the other hand, a small anisotropy of the relic background can tell a lot about the physics of the beginning of the universal expansion, where primordial cosmological perturbations, which later affect the relic isotropy, formed (see, e.g., [1,2] and other reviews on the early universe). We would like to emphasize another factor that forms mainly the large-scale structure of relic anisotropy: the spatial curvature of the background Friedmann Universe. In the light of the discovery of the large-scale anisotropy of the cosmic radiation [3–5], this problem becomes very important.

scholarly journals Note On A Super-Horizon-Scale Inhomogeneous Cosmological Model

1996 ◽  
Vol 173 ◽  
pp. 25-26
Author(s):  
K. Tomita
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Theoretical Explanation ◽  
Cosmological Models ◽  
Low Density ◽  
De Sitter ◽  
Number Count ◽  
Microwave Background Radiation ◽  
Sitter Model ◽  
De Sitter Model

Many observations of large-scale and cosmological structures in the universe have been collected, but so far there is no consistent theoretical explanation. In the region within 100 Mpc from us, the observed two-point correlations of galaxies and clusters of galaxies can be described well by low-density homogeneous cosmological models (Bahcall & Cen 1993; Suto 1993). On the other hand, the observed anisotropies of the cosmic microwave background radiation have been explained well by comparatively high-density cosmological models such as the Einstein-de Sitter model (Bunn & Sugiyama 1994). In the intermediate scale, the angular sizes of the cores of quasars have been measured and their redshift dependence has been shown to be more consistent with the Einstein-de Sitter model than with the low-density models (Kellermann 1993). The number count-magnitude relation for remote galaxies supports low-density models with a nonzero cosmological constant (for example, Fukugita et al. 1990), but these models may be inconsistent with the observed distribution of Lyα clouds (Fukugita & Lahav 1991).

DYNAMICS OF FERROMAGNETIC WALLS: GRAVITATIONAL PROPERTIES

2005 ◽  
Vol 14 (03n04) ◽  
pp. 521-541 ◽  
Author(s):  
L. CAMPANELLI ◽  
P. CEA ◽  
G. L. FOGLI ◽  
L. TEDESCO
Keyword(s):  
Domain Wall ◽  
Large Scale ◽  
Domain Walls ◽  
Background Radiation ◽  
Ideal Gas ◽  
Microwave Background ◽  
Electroweak Phase Transition ◽  
Microwave Background Radiation ◽  
The Universe ◽  
Negligible Contribution

We discuss a new mechanism which allows domain walls produced during the primordial electroweak phase transition. We show that the effective surface tension of these domain walls can be made vanishingly small due to a peculiar magnetic condensation induced by fermion zero modes localized on the wall. We find that in the perfect gas approximation the domain wall network behaves like a radiation gas. We consider the recent high-red shift supernova data and we find that the corresponding Hubble diagram is compatible with the presence in the Universe of an ideal gas of ferromagnetic domain walls. We show that our domain wall gas induces a completely negligible contribution to the large-scale anisotropy of the microwave background radiation.

scholarly journals DIVISION VIII: GALAXIES AND THE UNIVERSE

2008 ◽  
Vol 4 (T27A) ◽  
pp. 283-285
Author(s):  
Sadanori Okamura ◽  
Elaine Sadler ◽  
Francesco Bertola ◽  
Mark Birkinshaw ◽  
Françoise Combes ◽  
...  
Keyword(s):  
Computer Simulations ◽  
Large Scale ◽  
Background Radiation ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Wide Range ◽  
Microwave Background Radiation ◽  
The Universe

Division VIII provides a focus for astronomers studying a wide range of problems related to galaxies and cosmology. Objects of the study include individual galaxies, groups and clusters of galaxies, large scale structure, comic microwave background radiation and the universe itself. Approaches are diverse from observational one to theoretical one including computer simulations.

scholarly journals Dragging Force on Galaxies Due to Streaming Dark Matter

1990 ◽  
Vol 124 ◽  
pp. 645-649
Author(s):  
Tetsuya Hara ◽  
Shigeru Miyoshi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Rest Frame ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
The Universe

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.

scholarly journals ANISOTROPIC DARK ENERGY AND ELLIPSOIDAL UNIVERSE

2011 ◽  
Vol 20 (06) ◽  
pp. 1153-1166 ◽  
Author(s):  
L. CAMPANELLI ◽  
P. CEA ◽  
G. L. FOGLI ◽  
L. TEDESCO
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Background Radiation ◽  
Microwave Background ◽  
Anisotropic Dark Energy ◽  
Large Scale Geometry ◽  
Microwave Background Radiation ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

A cosmological model with anisotropic dark energy is analyzed. The amount of deviation from isotropy of the equation of state of dark energy, the skewness δ, generates an anisotropization of the large-scale geometry of the Universe, quantifiable by means of the actual shear Σ0. Requiring that the level of cosmic anisotropization at the time of decoupling be such that we can solve the "quadrupole problem" of cosmic microwave background radiation, we find that |δ| ~ 10-4 and |Σ_0| ~10-5, compatible with existing limits derived from the magnitude redshift data on Type Ia supernovae.

General relativistic cosmological models and the cosmic microwave background radiation

1986 ◽  
Vol 64 (2) ◽  
pp. 152-159 ◽  
Author(s):  
John D. Barrow
Keyword(s):  
Observational Studies ◽  
Background Radiation ◽  
Relativistic Effects ◽  
Cosmological Models ◽  
Total Density ◽  
Microwave Background ◽  
Small Deviations ◽  
Microwave Background Radiation ◽  
General Relativistic ◽  
The Universe

We survey recent theoretical ideas regarding the possible value of the present total density of the Universe and show how physically realistic cosmological models containing small deviations from isotropy allow observations of intrinsically general relativistic effects on the microwave background to determine whether or not the Universe is open or closed no matter how close the total density lies to the critical value. Applications of these results to inhomogeneous cosmological models, cosmic vorticity, and observational studies of the microwave-background-radiation isotropy are also discussed.

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