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Compensated Isocurvature Perturbations and the Cosmic Microwave Background
Compensated Isocurvature Perturbations Microwave Background
2011/10/19
Measurements of cosmic microwave background (CMB) anisotropies constrain isocurvature fluctuations between photons and non-relativistic particles to be sub-dominant to adiabatic fluctuations. Perturba...
Recent cosmological observations, including measurements of the CMB anisotropy and the primordial helium abundance, indicate the existence of an extra radiation component in the Universe beyond the st...
Manifestly gauge invariant theory of the nonlinear cosmological perturbations in the leading order of the gradient expansion
nonlinear cosmological perturbation, gauge invariance, non-Gaussianity PACS number(s):98.80.Cq
2011/9/29
In the full nonlinear cosmological perturbation theory in the leading order of the gradient expansion, all the types of the gauge invariant perturbation variables are defined. The metric junction cond...
General conditions for scale-invariant perturbations in an expanding universe
General conditions scale-invariant perturbations expanding universe
2011/9/29
We investigate the general properties of expanding cosmological models which generate scale-invariant curvature perturbations in the presence of a variable speed of sound. We show that in an expanding...