Pseudo-conformal Universe: late-time contraction and generation of tensor modes

TL;DR

This paper explores a bouncing Universe model with a contracting phase driven by a complex scalar field, analyzing the resulting tensor mode spectrum which is blue and of small amplitude, providing constraints on model parameters.

Contribution

It introduces a novel bouncing Universe scenario with a complex scalar field and calculates the tensor mode spectrum during contraction.

Findings

Tensor spectrum is blue and small in amplitude

Rapid contraction occurs in the classical evolution

Model parameters face mild observational constraints

Abstract

We consider a bouncing Universe model which explains the flatness of the primordial scalar spectrum via complex scalar field that rolls down its negative quartic potential and dominates in the Universe. We show that in this model, there exists a rapid contraction regime of classical evolution. We calculate the power spectrum of tensor modes in this scenario. We find that it is blue and its amplitude is typically small, leading to mild constraints on the parameters of the model.