Slow-Roll Inflation Preceded by a Topological Defect Phase \`a la Chaplygin Gas

TL;DR

This paper proposes a toy model where a network of frustrated topological defects precedes slow-roll inflation, potentially affecting the universe's expansion and gravitational wave spectrum, with implications for CMB anomalies and future detections.

Contribution

It introduces a Chaplygin gas-based model linking topological defect networks to inflationary dynamics and gravitational wave spectra, offering new insights into early universe scenarios.

Findings

Can produce slower inflation or constant expansion due to defect networks

Alleviates the quadruple anomaly in the CMB spectrum

Predicts gravitational wave spectra detectable by BBO and DECIGO

Abstract

We present a simple toy model corresponding to a network of frustrated topological defects of domain walls or cosmic strings that exist previous to the standard slow-roll inflationary era of the universe. Such a network (i) can produce a slower inflationary era than that of the standard scenario if it corresponds to a network of frustrated domain walls or (ii) can induce a vanishing universal acceleration; i.e., the universe would expand at a constant speed, if it corresponds to a network of frustrated cosmic strings red. Those features are phenomenologically modeled by a Chaplygin gas that can interpolate between a network of frustrated topological defects and a de Sitter-like or a power-law inflationary era. We show that this scenario can alleviate the quadruple anomaly of the cosmic microwave background spectrum. Using the method of the Bogoliubov coefficients, we obtain the spectrum of the gravitational waves as would be measured today for the whole range of frequencies. We comment on the possible detection of this spectrum by the planned detectors like BBO and DECIGO.