Exploring a string-like landscape

TL;DR

This study investigates inflationary trajectories in a two-dimensional string landscape model, revealing that sufficient inflation is rare but often consistent with current observations, with potential detectability in future experiments.

Contribution

It introduces a numerical analysis of inflation in a string-like landscape using two-field formalism, highlighting the rarity of sufficient inflation and the effects of isocurvature modes.

Findings

Sufficient inflation occurs in about 1 in 100,000 potentials.

Most models with sufficient inflation match current WMAP constraints.

Tensor-to-scalar ratio often detectable by future CMB experiments.

Abstract

We explore inflationary trajectories within randomly-generated two-dimensional potentials, considered as a toy model of the string landscape. Both the background and perturbation equations are solved numerically, the latter using the two-field formalism of Peterson and Tegmark which fully incorporates the effect of isocurvature perturbations. Sufficient inflation is a rare event, occurring for only roughly one in $10^5$ potentials. For models generating sufficient inflation, we find that the majority of runs satisfy current constraints from WMAP. The scalar spectral index is less than 1 in all runs. The tensor-to-scalar ratio is below the current limit, while typically large enough to be detected by next-generation CMB experiments and perhaps also by Planck. In many cases the inflationary consistency equation is broken by the effect of isocurvature modes.