Bouncing and Accelerating Solutions in Nonlocal Stringy Models

TL;DR

This paper explores non-local string-inspired cosmological models, revealing how phantom divide crossing arises from equivalence to models with infinite local fields, and presents stable bouncing and accelerating solutions.

Contribution

It introduces a class of non-local string-inspired models, analyzes the phantom divide crossing, and constructs exact, stable solutions with locking potentials.

Findings

Phantom divide crossing is caused by equivalence to models with infinite local fields.

Stable bouncing and accelerating solutions are constructed.

Deformations with locking potentials stabilize solutions.

Abstract

A general class of cosmological models driven by a non-local scalar field inspired by string field theories is studied. In particular cases the scalar field is a string dilaton or a string tachyon. A distinguished feature of these models is a crossing of the phantom divide. We reveal the nature of this phenomena showing that it is caused by an equivalence of the initial non-local model to a model with an infinite number of local fields some of which are ghosts. Deformations of the model that admit exact solutions are constructed. These deformations contain locking potentials that stabilize solutions. Bouncing and accelerating solutions are presented.