Domain walls, near-BPS bubbles, and probabilities in the landscape

TL;DR

This paper develops a theory of BPS domain walls in the string landscape, analyzing vacuum decay processes, and demonstrating how irreversible decay channels influence probability distributions in string cosmology.

Contribution

It introduces a comprehensive framework for BPS domain walls in various string vacua and explores their role in vacuum decay and probability flow in the landscape.

Findings

Decay rates of dS vacua to collapsing spaces can be large.

Irreversible decay channels act as sinks, affecting probability distributions.

Some vacua remain stable or metastable after uplifting.

Abstract

We develop a theory of static BPS domain walls in stringy landscape and present a large family of BPS walls interpolating between different supersymmetric vacua. Examples include KKLT models, STU models, type IIB multiple flux vacua, and models with several Minkowski and AdS vacua. After the uplifting, some of the vacua become dS, whereas some others remain AdS. The near-BPS walls separating these vacua may be seen as bubble walls in the theory of vacuum decay. As an outcome of our investigation of the BPS walls, we found that the decay rate of dS vacua to a collapsing space with a negative vacuum energy can be quite large. The parts of space that experience a decay to a collapsing space, or to a Minkowski vacuum, never return back to dS space. The channels of irreversible vacuum decay serve as sinks for the probability flow. The existence of such sinks is a distinguishing feature of the landscape. We show that it strongly affects the probability distributions in string cosmology.