Conflation: a new type of accelerated expansion

TL;DR

This paper introduces a novel cosmological model called conflation, combining features of inflation and ekpyrosis within scalar-tensor theories, with unique negative potentials and controlled fluctuation amplification.

Contribution

It constructs a new cosmological scenario that merges inflationary and ekpyrotic phases, featuring negative potentials and minimal fluctuation amplification, expanding the landscape of early universe models.

Findings

Conflation leads to accelerated expansion with negative potential energy.

The model avoids eternal inflation and infinities in fluctuation growth.

Adding a second scalar field can produce density fluctuations consistent with observations.

Abstract

In the framework of scalar-tensor theories of gravity, we construct a new kind of cosmological model that conflates inflation and ekpyrosis. During a phase of conflation, the universe undergoes accelerated expansion, but with crucial differences compared to ordinary inflation. In particular, the potential energy is negative, which is of interest for supergravity and string theory where both negative potentials and the required scalar-tensor couplings are rather natural. A distinguishing feature of the model is that, for a large parameter range, it does not significantly amplify adiabatic scalar and tensor fluctuations, and in particular does not lead to eternal inflation and the associated infinities. We also show how density fluctuations in accord with current observations may be generated by adding a second scalar field to the model. Conflation may be viewed as complementary to the recently proposed anamorphic universe of Ijjas and Steinhardt.