Supersymmetry Breaking and Stability in String Vacua: brane dynamics, bubbles and the swampland

Abstract

We review some aspects of the dramatic consequences of supersymmetry breaking on string vacua. In particular, we focus on the issue of vacuum stability in tendimensional string models with broken, or without, supersymmetry, whose perturbative spectra are free of tachyons. After formulating the models at stake, we introduce their unified low-energy effective description and present a number of vacuum solutions to the classical equations of motion. In addition, we present a generalization of previous no-go results for de Sitter vacua in warped flux compactifications. Then we analyze the classical and quantum stability of these vacua, studying linearized field fluctuations and bubble nucleation. Then, we describe how the resulting instabilities can be framed in terms of brane dynamics, examining in particular brane interactions, back-reacted geometries and commenting on a brane-world string construction along the lines of a recent proposal. After providing a summary, we conclude with some perspectives on possible future developments.

Minimal black holes and species thermodynamics

“…In such settings, weakly coupled (and possibly long-lived) vacua can be constructed [85] with suitable brane configurations, and supersymmetry breaking can renormalize and decrease the effective tension T of branes relative to their charge q [83,[86][87][88]. This renormalization is multiplicative, of the form T eff = q/(1 + δ), rather than additive as in the preceding settings.…”

De Sitter, gravitino mass and the swampland

“…The fact that supersymmetry has not been observed so far is thus very much compatible with the gravitino conjecture, which might point towards a scenario with supersymmetry breaking at high scale. This is naturally realised in string theory through a mechanism known as brane supersymmetry breaking [29,30] (see [31] for a recent review in a swampland perspective), in which the supersymmetry breaking scale is the string scale. Due to this fact, the effective descriptions of these models typically requires a non-linear realisation of supersymmetry in the low energy, which is not directly captured by the framework of [9,10].…”