A Terminal Velocity on the Landscape: Particle Production near Extra Species Loci in Higher Dimensions

TL;DR

This paper explores particle production near extra species loci in higher-dimensional field spaces, deriving a speed limit that enables a novel inflationary scenario with observationally consistent predictions and minimal fine-tuning.

Contribution

It introduces a universal terminal velocity in moduli space due to particle production near ESLs, enabling a new form of inflation without fine-tuning or specific initial conditions.

Findings

Derives a speed limit in moduli space independent of potential for large D

Shows inflation can occur at terminal velocity with over sixty e-folds

Constructs a viable model with red spectrum and suppressed gravitational waves

Abstract

We investigate particle production near extra species loci (ESL) in a higher dimensional field space and derive a speed limit in moduli space at weak coupling. This terminal velocity is set by the characteristic ESL-separation and the coupling of the extra degrees of freedom to the moduli, but it is independent of the moduli's potential if the dimensionality of the field space is considerably larger than the dimensionality of the loci, D >> d. Once the terminal velocity is approached, particles are produced at a plethora of nearby ESLs, preventing a further increase in speed via their backreaction. It is possible to drive inflation at the terminal velocity, providing a generalization of trapped inflation with attractive features: we find that more than sixty e-folds of inflation for sub-Planckian excursions in field space are possible if ESLs are ubiquitous, without fine tuning of initial conditions and less tuned potentials. We construct a simple, observationally viable model with a slightly red scalar power-spectrum and suppressed gravitational waves; we comment on the presence of additional observational signatures originating from IR-cascading and individual massive particles. We also show that moduli-trapping at an ESL is suppressed for D >> d, hindering dynamical selection of high-symmetry vacua on the landscape based on this mechanism.