Microscopic string analysis of the D0-D8 brane system and dual R-R states

TL;DR

This paper uses boundary state formalism to analyze the D0-D8 brane system, revealing how R-R potentials contribute to interactions and clarifying duality relations through a local string perspective.

Contribution

It constructs BRST invariant R-R vertex operators in an asymmetric picture and explains the non-zero R-R interaction in the D0-D8 system from a microscopic viewpoint.

Findings

R-R 1-form state overlaps with D0 and D8 branes

Null states are identified and removed to recover duality relations

Provides a local interpretation of R-R forces in the D0-D8 system

Abstract

Using the boundary state formalism, we perform a microscopic string analysis of the interaction between two D-branes and provide a local interpretation for the R-R force in the D0-D8 brane system. To do so, we construct BRST invariant vertex operators for the massless R-R states in the asymmetric picture that are proportional to potentials rather than field strengths. The Hilbert space of such R-R states contains combinations of two vectors that decouple from all physical amplitudes, even in the presence of boundaries. Identifying these vectors, we remove the null states and recover duality relations among R-R potentials. If we specify to the D0-D8 brane system, this mechanism implies that the R-R 1-form state has a non-zero overlap with both the D0-brane and the D8-brane, thus explaining from a local point of view the non-vanishing R-R contribution in the interaction for the D0-D8 brane system and those related to it by duality.