Paramount fluctuation of density

In Cosmology, the paramount fluctuations of density are the variations of Densité which were present at the beginning of the history of the Univers at the time of the Big Bang, and which is at the origin of the structure of the current universe. In the model of the cosmic Inflation, these variations find their origin in the quantum fluctuations present during the era of Planck. They have grows and became traditional fluctuations thereafter by accompanying the fast expansion which the universe at this stage knew. It is generally allowed that the observable universe was in balance Thermodynamique before this expansion and that without these fluctuations the universe would have been perfectly homogeneous, and that the Galaxie S and the Galaxy cluster would not have been formed.

The observations of the cosmological diffuse Fund and the Décalage towards the red are used to measure the distribution last and present of the Matière and the Rayonnement. Thanks to these observations, important characteristics of these paramount fluctuations could be measured and were in remarkable agreement with the predictions made by the cosmic Inflation. In addition these measurements also could make it possible to deduce from the strong constraints on the cosmological parameters fundamental.

Formalism

The paramount fluctuations are typically quantified by a spectrum of the intensity of the variations according to the space scales. Within this formalism, the density of mass fractional is defined by:

\ delta (\ vec {X}) \ equiv \ frac {\ rho (\ vec {X})}{\ bar {\ rho}} - 1 =

\ sum_k \ delta_k e^ {I \ vec {K} \ cdot \ vec {X}} where

\ bar {\ rho}

is the density of average mass. Several inflationary models predict a behavior of the fluctuations like a function power of the type

P_s (K) \ propto k^n

where

k

is the Nombre of wave fluctuations in Mpc⁻¹ and for which

P (K) \ equiv |\ delta_k|^2

For scalar fluctuations,

n + 1

is called scalar index . The model where

n = 0

corresponds to the invariant of scale of the fluctuations.

Fluctuations adiabat/isocourbure

The adiabatic fluctuations are variations of density for the matter or the energy in which the fractional surdensities and under-densities are equal. For example, an adiabatic surdensity of photons of factor two would also correspond to a surdensity of electrons of factor two. In fluctuations in mode Isocourbure , a density of variations of the one of the components does not correspond to an equivalent density for another component. Whereas it is generally supposed that the paramount fluctuations were adiabatic, one can think that the current data plead in favor of a variation of density in isocourbure mode. Although one cannot draw from conclusion on the whole of the constraints, the isocourbure modes not-correlated of the black Matière cold are improbable.

Modes of tensors

The inflationary model predicts the presence of paramount fluctuations of a tensor, appearing by gravitational waves. In a way similar to the scalar fluctuations, it is thought that those follow a law of power and are paramétrisées by an index of tensor and the ratio of the tensor compared to the scalar power.

External references and bonds

Crotty, Patrick, " Bounds one isocurvature disturbances from CMB and LSS dated ". Physical Review Letters.
Linde, Andrei, " Quantum Cosmology and the Structure off Inflationary Universe ". Invited talk.
Peiris, Hiranya, " First Year Wilkinson Microwave Anisotropy Honest (WMAP) Observations: Implications for Inflation ". Astrophysical Newspaper.
Tegmark, max, " Cosmological parameters from SDSS and WMAP ". Physical Review D.

See too

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