Preinflationary primordial perturbations

Abstract

The large-scale power deficit in the cosmic microwave background fluctuations might be relevant with the physics of pre-inflation, a bounce, or a superinflationary phase preceding slow-roll inflation, which can provide a singular-free realization of inflation. We investigate the primordial perturbations from such pre-inflationary evolutions, which generally may consist of multiple phases with different background dynamics, and give a universal formula for the power spectrum of primordial perturbations in terms of the recursive Bogoliubov coefficients. We also apply our formula to corresponding cases and show how the intensity of large-scale power suppression is affected by the pre-inflationary physics.

Propagating speed of primordial gravitational waves and inflation

“…Since the amplitude of the primordial GWs is determined by c T and the Hubble radius ∼ H −1 , the running of c T will inevitably affect the power spectrum of primordial GWs (see also [27] for the study from the point of view of the running of GWs' refractive index n). It was found in [28] [29] that the oscillation of c T may leave some observable imprints in CMB B-mode polarization. The effect of the sound speed c S of scalar perturbation on the scalar spectrum has been investigated in e.g.…”

Oscillation in power spectrum of primordial gravitational wave as a signature of higher-order stringy corrections

“…Both are the imprints of the primordial GWs. The detection of the recombination peak will be a confirmation that inflation has ever occurred, while detecting the reionization bump at low-l would help us to understand the physics of pre-inflationary universe, e.g., [39]. When the comoving oscillating scale in GWs power spectrum is set at l ≈ 80, for r 0.01 we may see obvious wiggles around the recombination peak, which may be tested by the upcoming polarization data.…”

Gauss-Bonnet cosmology unifying late and early-time acceleration eras with intermediate eras

“…In fact, in the literature there exist various cosmological scenarios for this pre-inflationary era, in which case a crushing singularity might or might not occur, see for example [39][40][41][42]. However, in our case the focus will be on later times and particularly for times near the beginning of inflation and after.…”