Tachyon - Dilaton driven Inflation as an alpha' - non-perturbative solution in First Quantized String Cosmology

TL;DR

This paper constructs exact non-perturbative inflationary solutions in string cosmology using a novel functional method, revealing a mechanism involving tachyon and dilaton backgrounds that produce short inflationary periods without horizons, compatible with string theory.

Contribution

It introduces a non-perturbative approach to find exact inflationary solutions in string theory, valid in four dimensions, with a novel alignment mechanism between tachyon and dilaton backgrounds.

Findings

Exact non-perturbative inflationary solutions constructed.

Solutions have no cosmological horizons, enabling well-defined scattering amplitudes.

Potential for studying string production during preheating.

Abstract

Applying a novel non-perturbative functional method framework to a two-dimensional bosonic sigma model with tachyon, dilaton and graviton backgrounds we construct exact (non perturbative in the Regge slope) inflationary solutions, consistent with world-sheet Weyl Invariance. The mechanism for inflation entails a (partial) "alignment" between tachyon and dilaton backgrounds in the solution space. Some cosmological solutions which contain inflationary eras for a short period and interpolate between flat universes in the far past and far future are also discussed. These solutions are characterized by the absence of cosmological horizons, and therefore have well-defined scattering amplitudes. This makes them compatible with a perturbative string framework, and therefore it is these solutions that we consider as self-consistent in our approach. Within the context of the interpolating solutions, string production at the end of inflation (preheating) may also be studied. The advantage of our method is that the solutions are valid directly in four target-space-time dimensions, as a result of the non trivial dilaton configurations.