Bubble needs strings

TL;DR

This paper highlights the crucial role of strings in modeling de Sitter space with an expanding bubble, offering a novel perspective on matter sourcing and addressing time dependence issues in such models.

Contribution

It introduces the use of string endpoints to source gravity on the bubble wall, providing a new interpretation of volume divergence as mass renormalization and resolving residual time dependence.

Findings

Strings can source gravity on the bubble wall.

Volume divergence can be seen as mass renormalization.

Time dependence issues are naturally resolved with string sources.

Abstract

In this paper, we want to emphasize the pivotal role played by strings in the model realizing de Sitter using an expanding bubble, proposed and subsequently developed in arXiv:1807.01570, arXiv:1907.04268, and arXiv:2001.07433. Contrary to the Randall-Sundrum model of brane-localized gravity, we use the end points of radially stretched strings to obtain matter sourcing gravity induced on the bubble wall. This allows us to reinterpret the possible volume divergence coming from naive dimensional reduction as mass renormalization in four dimensional particle physics. Furthermore, we argue that the residual time dependence in the bulk, pointed out by some recent work as a possible shortcoming of such models, is automatically cured in presence of these stringy sources.