Decreasing density perturbations and the isotropy of the cosmic microwave background

1988 ◽  
Vol 102 (5) ◽  
pp. 517-522
Author(s):  
S. Motta
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Density Perturbations

scholarly journals DENSITY PERTURBATIONS, GRAVITY WAVES AND THE COSMIC MICROWAVE BACKGROUND

1992 ◽  
Vol 07 (38) ◽  
pp. 3541-3551 ◽  
Author(s):  
TARUN SOURADEEP ◽  
VARUN SAHNI
Keyword(s):  
Cosmic Microwave Background ◽  
Gravity Waves ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Density Perturbation ◽  
Microwave Background ◽  
Relative Contribution ◽  
Microwave Background Radiation ◽  
Density Perturbations

We assess the contribution to the observed large scale anisotropy of the cosmic microwave background radiation, arising from both gravity waves as well as adiabatic density perturbations, generated by a common inflationary mechanism in the early Universe. We find that for inflationary models predicting power law primordial spectra |δk|2∝kn, the relative contribution to the quadrupole anisotropy from gravity waves and scalar density perturbations, depends crucially upon n. For n<0.84, gravity waves perturb the CMBR by a larger amount than density perturbations, whereas for n>0.84 the reverse is true. Normalizing the amplitude of the density perturbation spectrum at large scales, using the observed value of the COBE quadrupole, we determine (δM/M)16-the rms density contrast on scales [Formula: see text] Mpc, for cosmological models with cold dark matter. We find that for n<0.75, a large amount of biasing is required in order to reconcile theory with observations. We also determine the value of the inflationary Hubble parameter and the COBE-normalized amplitude and spectrum of gravity waves from inflation.

scholarly journals PROBING THE ANISOTROPIC EXPANSION HISTORY OF THE UNIVERSE WITH COSMIC MICROWAVE BACKGROUND

2012 ◽  
Vol 27 (24) ◽  
pp. 1250144 ◽  
Author(s):  
RANJITA K. MOHAPATRA ◽  
P. S. SAUMIA ◽  
AJIT M. SRIVASTAVA
Keyword(s):  
Cosmic Microwave Background ◽  
Background Radiation ◽  
Microwave Background ◽  
Anisotropic Expansion ◽  
Microwave Background Radiation ◽  
Expansion Stage ◽  
History Of ◽  
Density Perturbations ◽  
Expansion Of The Universe ◽  
The Universe

We propose a simple technique to detect any anisotropic expansion stage in the history of the universe starting from the inflationary stage to the surface of last scattering from the cosmic microwave background radiation (CMBR) data. We use the property that any anisotropic expansion in the universe would deform the shapes of the primordial density perturbations and this deformation can be detected in a shape analysis of superhorizon fluctuations in CMBR. Using this analysis we obtain the constraint on any previous anisotropic expansion of the universe to be less than about 35%.

scholarly journals ON AXIAL AND PLANE-MIRROR INHOMOGENEITIES IN THE WMAP3 COSMIC MICROWAVE BACKGROUND MAPS

2007 ◽  
Vol 22 (39) ◽  
pp. 2955-2964 ◽  
Author(s):  
V. G. GURZADYAN ◽  
A. A. STAROBINSKY ◽  
A. L. KASHIN ◽  
H. G. KHACHATRYAN ◽  
G. YEGORIAN
Keyword(s):  
Cosmic Microwave Background ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Temperature Threshold ◽  
Microwave Background ◽  
Excursion Sets ◽  
Noise Structure ◽  
Spatial Coordinates ◽  
Density Perturbations ◽  
Temperature Maps ◽  
Topology Of The Universe

We study inhomogeneities in the distribution of the excursion sets in the Cosmic Microwave Background (CMB) temperature maps obtained by the three years survey of the Wilkinson Microwave Anisotropy Probe (WMAP). At temperature thresholds |T| = 90 μ K , the distributions of the excursion sets with over 200 pixels are concentrated in two regions, nearly at the antipodes, with galactic coordinates l = 94.7°, b = 34.4° and l = 279.8°, b = -29.2°. The centers of these two regions drift towards the equator when the temperature threshold is increased. The centers are located close to one of the vectors of ℓ = 3 multipole. The two patterns of the substructures in the distribution of the excursion sets are mirrored, with χ2 = 0.7–1.5. There is no obvious origin of this effect in the noise structure of WMAP, and there is no evidence for a dependence on the galactic cut. Would this effect be cosmological, it could be an indication of an anomalously large component of horizon-size density perturbations, independent of one of the spatial coordinates, and/or of a non-trivial slab-like spatial topology of the Universe.

Small‐Scale Cosmic Microwave Background Observations at 8.4 GHz

1997 ◽  
Vol 483 (1) ◽  
pp. 38-50 ◽  
Author(s):  
R. Bruce Partridge ◽  
Eric A. Richards ◽  
Edward B. Fomalont ◽  
K. I. Kellerman ◽  
Rogier A. Windhorst
Keyword(s):  
Cosmic Microwave Background ◽  
Small Scale ◽  
Microwave Background

scholarly journals The evolution of the cosmic microwave background temperature

2011 ◽  
Vol 526 ◽  
pp. L7 ◽  
Author(s):  
P. Noterdaeme ◽  
P. Petitjean ◽  
R. Srianand ◽  
C. Ledoux ◽  
S. López
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature
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