D-brane - Anti-D-brane forces in plane wave backgrounds: A fall from grace

We study the nature of the force between a D-brane and an anti-D-brane in the maximally supersymmetric plane wave background of type IIB superstring theory, which is equipped with a mass parameter μ. An early such study in flat spacetime (μ = 0) served to sharpen intuition about D-brane interactions, showing in particular the key role of the 'stringy halo' that surrounds a D-brane. The halo marks the edge of the region within which tachyon condensation occurs, opening a gateway to new non-trivial vacua of the theory. It seems pertinent to study the fate of the halo for non-zero μ. Focusing on the simplest cases of p=+1,-1, we find here that for branes located at the origin, the radius of the halo shrinks for increasing μ. For branes away from the origin, this shrinking persists, and is accompanied by a shift of the centre of the halo away from the D-brane. In fact, we observe that for large enough μ, or beyond a critical distance from the origin, D-branes can lose their halo entirely! We suspect that the consequences of this physics for key notions about the dynamics, stability and classification of D-branes (such as tachyon condensation, K-theory, etc.,) may well be quite significant. (author)