Comments on geometric and universal open string tachyons near fivebranes

TL;DR

This paper demonstrates that in NS5-brane backgrounds, the universal open string tachyon and the geometric tachyon are equivalent by analyzing a specific non-BPS D-brane configuration using boundary worldsheet CFT methods.

Contribution

It provides a concrete example showing the equivalence of universal and geometric tachyons in a curved background, extending previous theoretical arguments.

Findings

Universal and geometric tachyons are shown to be identical in a specific D-brane setup.

Boundary worldsheet CFT methods confirm the equivalence of the two tachyon types.

The study supports the idea that tachyonic instabilities can be unified in curved backgrounds.

Abstract

In a recent paper (hep-th/0703157), Sen studied unstable D-branes in NS5-branes backgrounds and argued that in the strong curvature regime the universal open string tachyon (on D-branes of the wrong dimensionality) and the geometric tachyon (on D-branes that are BPS in flat space but not in this background) may become equivalent. We study in this note an example of a non-BPS suspended D-brane vs. a BPS D-brane at equal distance between two fivebranes. We use boundary worldsheet CFT methods to show that these two unstable branes are identical.