Visible Branes with Negative Tension in Heterotic M-Theory

TL;DR

This paper demonstrates the existence of heterotic M-theory vacua with negative tension on the visible brane, positive tension on the hidden brane, and small bulk five-brane tension ratios, challenging previous claims.

Contribution

It provides explicit examples of such vacua and shows the ratio of five-brane to visible brane tension can be made arbitrarily small, supporting Ekpyrotic cosmology models.

Findings

Existence of vacua with negative visible brane tension.

Explicit examples of these vacua are constructed.

The tension ratio beta/|alpha| can be made arbitrarily small.

Abstract

It is shown that there exist large classes of BPS vacua in heterotic M-theory which have negative tension on the visible orbifold plane, positive tension on the hidden plane and positive tension, physical five-branes in the bulk space. Explicit examples of such vacua are presented. Furthermore, it is demonstrated that the ratio, beta/|alpha|, of the bulk five-brane tension to the visible plane tension can, for several large classes of such vacua, be made arbitrarily small. Hence, it is straightforward to find vacua with the properties required in the examples of the Ekpyrotic theory of cosmology - a visible brane with negative tension and beta/|alpha| small. This contradicts recent claims in the literature.