Abstract
A variable speed of light (VSL) cosmology is described in which the causal mechanism of generating primordial perturbations is achieved by varying the speed of light in a primordial epoch. This yields an alternative to inflation for explaining the formation of the cosmic microwave background (CMB) and the large scale structure (LSS) of the universe. The initial value horizon and flatness problems in cosmology are solved. The model predicts primordial scalar and tensor fluctuation spectral indices $n_s=0.96$ and $n_t=- 0.04$, respectively. We make use of the $\delta{\cal N}$ formalism to identify signatures of primordial nonlinear fluctuations, and this allows the VSL model to be distinguished from inflationary models. In particular, we find that the parameter $f_{\rm NL}=5$ in the variable speed of light cosmology. The value of the parameter $g_{\rm NL}$ evolves during the primordial era and shows a running behavior.
Highlights
Inflationary models have been successful in fitting cosmological data [1], there have been issues raised about the fundamental consequences of the models [2]
The Lorentz group S O(3, 1) is spontaneously broken resulting in SO(3,1)→ O(3) × R, where R is the absolute preferred time corresponding to the comoving time t in the preferred frame associated with the Friedmann-Lemaître-Robertson-Walker (FLRW) metric
In variable speed of light (VSL) models, the universe is still expanding with an effective equation of state parameter w = 1, and as a result, the dominant perturbation grows as a logarithmic function
Summary
Inflationary models have been successful in fitting cosmological data [1], there have been issues raised about the fundamental consequences of the models [2]. The total action contains an action for a minimally coupled scalar “seed” field φ, which will produce quantum primordial fluctuations It contains an action inducing a spontaneous violation of Lorentz invariance [11,12,28,29,30,31] by means of a nonvanishing vacuum expectation value of a vector field ψμ. The VSL cosmology can remove the fine-tuning of the initial values in the standard big-bang cosmology and fit the available observational data, such as an almost scale invariant, adiabatic and Gaussian scalar matter power spectrum and the potential observation of a gravitational wave power spectrum. C (2016) 76:130 and not require a multiverse scenario in the form of eternal inflation
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