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(Abridged) Does inflation have to happen all in one go? The answer is a resounding no! All cosmological problems can be solved by a sequence of short bursts of cosmic acceleration, interrupted by short epochs of decelerated expansion. The spectrum of perturbations will still match the CMB and LSS if the earliest stage of the last ${cal O}(50)-{cal O}(60)$ efolds is at least ${cal O}(15)$ efolds long. Other stages can be considerably shorter. But as long as they add up to ${cal O}(50)-{cal O}(60)$ efolds and the stages of decelerated expansion in between them are shorter and also overall last less, the ensuing cosmology will pass muster. The presence of the interruptions resets the efold clock of each accelerating stage, and changes its value at the CMB pivot point. This change opens up the theory space, loosening the bounds. In particular some models that seem excluded at ${cal N}=60$ fit very well as shorter stages with ${cal N}=30$. Interesting predictions are that both the scalar and tensor spectra of perturbations are rapidly modified at short wavelengths. These features could be tested with future CMB spectroscopy searches and with short wavelength primordial gravity probes. The spatial curvature in these models can be larger than the largest wavelength scalar perturbations, because $Omega_{tt k}$ evolves differently than the scalar perturbations $frac{delta rho}{rho}|_{tt S}$. Finally, with many short stages of accelerated expansion, the abundance of reheating products from previous accelerated stages does not get completely wiped out. This implies that the universe may contain additional populations of particles, more rare than the visible ones, or even primordial black holes, created during a late decelerated epoch before last reheating, which may be dark matter.
We discuss minisuperspace models within the framework of varying physical constants theories including $Lambda$-term. In particular, we consider the varying speed of light (VSL) theory and varying gravitational constant theory (VG) using the specific
In this paper, we have worked on the possibility of setting up an Bells inequality violating experiment in the context of primordial cosmology following the fundamental principles of quantum mechanics. To set up this proposal we have introduced a mod
We study the implications of the recently proposed Trans-Planckian Censorship Conjecture (TCC) for early universe cosmology and in particular inflationary cosmology. The TCC leads to the conclusion that if we want inflationary cosmology to provide a
While many aspects of general relativity have been tested, and general principles of quantum dynamics demand its quantization, there is no direct evidence for that. It has been argued that development of detectors sensitive to individual gravitons is
I review the Trans-Planckian Censorship Conjecture (TCC) and its implications for cosmology, in particular for the inflationary universe scenario. Whereas the inflationary scenario is tightly constrained by the TCC, alternative early universe scenarios are not restricted.