Mirror branes

TL;DR

This paper generalizes the Randall-Sundrum two-brane model by allowing branes with actions of the same form but opposite signs, analyzing stability, gravitational behavior, and quantum implications of the resulting setup.

Contribution

It introduces a new class of two-brane models with opposite sign actions, exploring their stability, gravitational properties, and quantum vacuum implications.

Findings

Model is tachyon-free for large negative brane cosmological constants

Gravitational forces on the branes are of opposite signs

Most realistic model localizes gravity around the visible brane

Abstract

The Randall-Sundrum two-brane model admits the flat-brane Lorentz-invariant vacuum solution only if the branes have exactly opposite tensions. We pay attention to this condition and propose a generalization of this model in which two branes are described by actions of the same form and with the same matter content but {\em with opposite signs}. In this way, the relation between their tensions (which are their vacuum energy densities) is naturally accounted for. We study a simple example of such a model in detail. It represents the Randall-Sundrum model supplemented by the Einstein scalar-curvature terms in the actions for the branes. We show that this model is tachyon-free for sufficiently large negative values of the brane cosmological constant, that gravitational forces on the branes are of opposite signs, and that physically most reasonable model of this type is the one where the five-dimensional gravity is localized around the visible brane. The massive gravitational modes in this model have ghost-like character, and we discuss the significance of this fact for the quantum instability of the vacuum on the visible brane.