scholarly journals Density perturbations of quantum-mechanical origin and anisotropy of the microwave background

1994 ◽  
Vol 50 (12) ◽  
pp. 7154-7172 ◽  
Author(s):  
L. P. Grishchuk
Keyword(s):  
Quantum Mechanical ◽  
Microwave Background ◽  
Density Perturbations

scholarly journals Anisotropy of the Microwave Background and Biased Galaxy Formation

1988 ◽  
Vol 130 ◽  
pp. 43-50
Author(s):  
Nick Kaiser
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Microwave Background ◽  
Galaxy Clustering ◽  
Clear View ◽  
Hot Gas ◽  
Density Perturbations ◽  
The Universe ◽  
Theoretical Developments

Fluctuations in the microwave background will have been imprinted at z ≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.

Are we falling into the Virgo Cluster?

1981 ◽  
Vol 4 (2) ◽  
pp. 172-177 ◽  
Author(s):  
N. Visvanathan
Keyword(s):  
Hubble Constant ◽  
Virgo Cluster ◽  
Microwave Background ◽  
Mean Velocity ◽  
Distant Galaxies ◽  
Induced Motion ◽  
Density Perturbations ◽  
Peculiar Motion ◽  
The Mean ◽  
The Universe

One of the important discoveries of astronomy is that the Universe expands: distant galaxies have large recession velocities in direct proportion to their distances. Attempts to determine a global value for the constant of proportionality between the velocity and the distance (Hubble constant) are met with difficulties by the presence of peculiar, random and streaming motions in the local region. These peculiar motions are either of primordial origin or the effect of density perturbations. These affect the mean velocity of the nearby groups in the level of 50-100 km/sec (Tammann, Sandage and Yahil 1980). However, the expected peculiar gravitationally induced motion of the Local Group towards the Virgo cluster, could be large due to the high density contrast in that direction (Sciama 1967; de Vaucouleurs and Peters 1968; Sandage, Tammann and Hardy 1972; Jones 1976). This infall motion could be as high as 500 km/sec if the anisotropy of the microwave background is interpreted to have a component of our peculiar motion towards the Virgo cluster (Peebles 1971, Boughn, Cheng and Wilkinson 1981; Gorenstein and Smoot 1981).

scholarly journals CMB: Anisotropies Due to Non-Linear Clustering

1996 ◽  
Vol 168 ◽  
pp. 445-446
Author(s):  
E. Martínez-González ◽  
J. L. Sanz
Keyword(s):  
Linear Density ◽  
Gravitational Effect ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Gravitational Fields ◽  
Hot Gas ◽  
Peculiar Velocities ◽  
Non Linear ◽  
Density Perturbations ◽  
The Universe

Most of the studies on the anisotropy expected in the temperature of the cosmic microwave background (CMB) have been based on linear density perturbations. The anisotropies at angular scales ≥ 1o(horizon at recombination) are preserved during the evolution of the universe, whereas for smaller scales new effects can appear, generated during the non-linear phase of matter clustering evolution: i) the Sunyaev-Zeldovich effect due to hot gas in clusters (Scaramella et al. 1993), ii) the Vishniac effect (Vishniac 1987) due to the coupling between density fluctuations and bulk motions of gas and iii) the integrated gravitational effect (Martínez–González et al. 1994) due to time-varyng gravitational potentials. A single potential φ(t, x), satisfying the Poisson equation, is enouph to describe weak gravitational fields associated to non-linear density fluctuations when one considers scales smaller than the horizon and non-relativistic peculiar velocities. The temperature anisotropies, in a flat universe, are given by the expression (Martínez–González et al. 1990)

scholarly journals ON THE CONTRIBUTION OF DENSITY PERTURBATIONS AND GRAVITATIONAL WAVES TO THE LOWER ORDER MULTIPOLES OF THE COSMIC MICROWAVE BACKGROUND RADIATION

2002 ◽  
Vol 11 (02) ◽  
pp. 259-297 ◽  
Author(s):  
A. DIMITROPOULOS ◽  
L. P. GRISHCHUK
Keyword(s):  
Dipole Moment ◽  
Gravitational Waves ◽  
Lower Order ◽  
Background Radiation ◽  
Infrared Divergence ◽  
Red Shift ◽  
Horizontal Line ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Density Perturbations

The important studies of Peebles, and Bond and Efstathiou have led to the formula Cℓ= const. /[ℓ(ℓ+1)] aimed at describing the lower order multipoles of the CMBR temperature variations caused by density perturbations with the flat spectrum. Clearly, this formula requires amendments, as it predicts an infinitely large monopole C0, and a dipole moment C1 only 6/2 times larger than the quadrupole C2, both predictions in conflict with observations. We restore the terms omitted in the course of the derivation of this formula, and arrive at a new expression. According to the corrected formula, the monopole moment is finite and small, while the dipole moment is sensitive to short-wavelength perturbations, and numerically much larger than the quadrupole, as one would expect on physical grounds. At the same time, the function ℓ(ℓ+1)Cℓ deviates from a horizontal line and grows with ℓ, for ℓ≥2. We show that the inclusion of the modulating (transfer) function terminates the growth and forms the first peak, recently observed. We fit the theoretical curves to the position and height of the first peak, as well as to the observed dipole, varying three parameters: red-shift at decoupling, red-shift at matter-radiation equality, and slope of the primordial spectrum. It appears that there is always a deficit, as compared with the COBE observations, at small multipoles, ℓ~10. We demonstrate that a reasonable and theoretically expected amount of gravitational waves bridges this gap at small multipoles, leaving the other fits as good as before. We show that the observationally acceptable models permit somewhat "blue" primordial spectra. This allows one to avoid the infrared divergence of cosmological perturbations, which is otherwise present.

COSMOLOGY WITH CLUSTERS OF GALAXIES

2005 ◽  
Vol 20 (06) ◽  
pp. 1121-1131
Author(s):  
M. DONAHUE
Keyword(s):  
Initial Density ◽  
Cosmological Parameters ◽  
Matter Density ◽  
Type Ia Supernovae ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Type Ia ◽  
Density Perturbations ◽  
The Mean ◽  
Ia Supernovae

Cluster observations provide unique and useful constraints on cosmological parameters. The contents of clusters and the rate of their formation are very sensitive to the mean matter density (ΩM and the normalization and shape of the spectrum of initial density perturbations near the size scale of ~8h-1 Mpc . Future and on-going cluster studies constrain ΩΛ (acceleration) and the equation of state of the "dark energy," particularly in conjunction with either constraints from the cosmic microwave background or Type Ia supernovae of white dwarfs.

scholarly journals Density Perturbations of Thermal Origin During Inflation

1997 ◽  
Vol 06 (03) ◽  
pp. 305-322 ◽  
Author(s):  
Wolung Lee ◽  
Li-Zhi Fang
Keyword(s):  
Heat Bath ◽  
Density Perturbation ◽  
Mass Scale ◽  
Inflationary Universe ◽  
Microwave Background ◽  
Thermally Induced ◽  
Fluctuation Dissipation ◽  
Thermal Origin ◽  
Density Perturbations ◽  
Adiabatic Case

We study thermally induced density perturbations during inflation. This scenario is characterized by two thermodynamical conditions: (1) The primordial perturbations originate in the epoch when the inflationary universe contains a thermalized heat bath. (2) The perturbations of the inflationary scalar field are given by the fluctuation–dissipation relation. We show that the spectrum of the primordial perturbations is of power law, but tilted, and there is a relation between the amplitude and the index of the power spectrum. Aside from the mass scale of the inflation, the amplitude–index relation does not depend on the other parameters like g-factor. These results are found to be well consistent with observations of the temperature fluctuations of cosmic microwave background if the mass scale of the inflation is about 1015  GeV . Instead of the purely adiabatic case, the consequent density perturbation is an admixture of adiabatic and isocurvature one. Therefore, the detection of super-Hubble suppression of the spectrum would be effective for further discrimination between the thermally originated models and others.

ANALYSIS OF PRIMORDIAL NON-GAUSSIANITIES IN CMB DATA

2011 ◽  
Vol 03 ◽  
pp. 266-275
Author(s):  
MARCOS A. GARCIA ◽  
ARMANDO BERNUI ◽  
THIAGO FERREIRA ◽  
ADHIMAR F. OLIVEIRA ◽  
ALISON DE O. MORAES
Keyword(s):  
Temperature Fluctuations ◽  
Observational Cosmology ◽  
Microwave Background ◽  
Local Type ◽  
Precise Data ◽  
The Standard Model ◽  
Density Perturbations ◽  
Wavelets Transform ◽  
Dominant Paradigm ◽  
Rule Out

In less than twenty years cosmology has evolved from being a theoretical endeavor to a science where observational data is becoming so precise that can rule out, or confirm, models and theories. This spectacular advance in observational cosmology was mainly due to the COBE and WMAP satellites which mapped the cosmic microwave background (CMB) radiation. In particular, the recent high quality measurements from WMAP-7yr constitute at present the most precise data to understand physics of the very early universe. In the standard model of cosmology, inflation is considered the dominant paradigm for the generation of the primordial density perturbations regarded as the seeds for structure formation. A powerful probe to investigate the nature of these primordial seeds is performed through the analysis of Gaussian deviations in the temperature fluctuations of the CMB. In fact, present and forthcoming CMB data may be sensitive enough to detect tiny Gaussian deviations induced by small non-linear primordial perturbations at the inflation era. Here we investigate the use of wavelets transform in the analyses of small non-Gaussianities of local type in CMB data from WMAP-7yr.

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