Limits on Semiclassical Fluctuations in the Primordial Universe

TL;DR

This paper investigates limits on semiclassical fluctuations in the early universe's primordial perturbations, analyzing models that break isotropy and using WMAP data to set upper bounds on their amplitudes.

Contribution

It introduces and tests two models of semiclassical primordial fluctuations that break isotropy, providing new constraints from observational data.

Findings

Upper bound for a single Fourier mode fluctuation: a <= 10^(-4)

Upper bound for a Gaussian bump fluctuation: a <= 10^(-3)

Constraints derived from seven-year WMAP data using Bayesian analysis

Abstract

We place limits on semiclassical fluctuations that might be present in the primordial perturbation spectrum. These can arise if some signatures of pre-inflationary features survive the expansion, or could be created by whatever mechanism ends inflation. We study two possible models for such remnant fluctuations, both of which break the isotropy of CMB on large scales. We first consider a semiclassical fluctuation in one Fourier mode of primordial perturbations. The second scenario we analyze is a semiclassical Gaussian bump somewhere in space. These models are tested with the seven-year WMAP data using a Markov Chain Monte Carlo Bayesian analysis, and we place limits on these fluctuations. The upper bound for the amplitude of a fluctuation in a single Fourier mode is a<=10^(-4), while for the Gaussian bump a<=10^(-3).