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Register a new userAnalysis on the evolution of $sigma_8(z)$ from Linear Nash-Greene fluctuations
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From the linear Nash-Greene fluctuations of background metric, we present the perturbation equations in an embedded four space-time. In the context of a five-dimensional bulk, we show that the perturbations are only propagated by the gravitational tensorial field equation. In Newtonian conformal gauge, we study the matter density evolution in sub-horizon regime and on how such scale may be affected by the extrinsic curvature. We apply a joint likelihood analysis to the data with the Markov Chain Monte Carlo (MCMC) method for cosmological parameter estimation using a pack of recent datasets as the Pantheon Supernovae type Ia, the Baryon Acoustic Oscillations (BAO) from DR12 galaxy sample and Dark Energy Survey (DES) Y$1$. The constrained parameters are tested in the cosmography analysis on the evolution of Hubble function $H(z)$ and the deceleration parameter $q(z)$, as well as on the evolution of the growth rate $fsigma_8(z)$ of the extended Gold 2018 growth-rate dataset with 25 datapoints. Moreover, we obtain an alleviation of the $sigma$ tension in the contours between ($sigma_8$-$Omega_m$) of the observations from Cosmic Microwave Background (CMB) and large scale structure (LSS) probes.
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In this paper we study the corrections to the Friedmann equations due to fast fluctuations of the universe scale factor. Such fast quantum fluctuations were recently proposed as a potential solution of the cosmological constant problem. They also induce strong changes to the current sign and magnitude of the average cosmological force, thus making it one of the potential probable causes for the modification of Newtonian dynamics in galaxy-scale systems. It appears that quantum fluctuations of the scale factor also modify the Friedmann equations, leading to considerable modification of cosmological evolution. In particular, they give rise to late-time accelerated expansion of the universe, and they may also considerably modify the effective universe potential.
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