Spiky strings in de Sitter space

TL;DR

This paper explores semiclassical spiky strings in de Sitter space, revealing a maximum spin per trajectory due to acceleration, and discusses implications for high-energy string scattering and the spectrum of higher spin states.

Contribution

It generalizes the analysis of spiky strings from anti-de Sitter to de Sitter space, highlighting the maximum spin constraint and the need for infinitely many trajectories for high-energy states.

Findings

Each Regge trajectory has a maximum spin due to de Sitter acceleration.

Maintaining high-energy string scattering requires infinitely many trajectories.

The spectrum includes infinitely many higher spin states with increasing folding number.

Abstract

We study semiclassical spiky strings in de Sitter space and the corresponding Regge trajectories, generalizing the analysis in anti-de Sitter space. In particular we demonstrate that each Regge trajectory has a maximum spin due to de Sitter acceleration, similarly to the folded string studied earlier. While this property is useful for the spectrum to satisfy the Higuchi bound, it makes a nontrivial question how to maintain mildness of high-energy string scattering which we are familiar with in flat space and anti-de Sitter space. Our analysis implies that in order to have infinitely many higher spin states, one needs to consider infinitely many Regge trajectories with an increasing folding number.