D-brane Analyses for BPS Mass Spectra and U-duality

TL;DR

This paper confirms U-duality in type II superstring theory by analyzing BPS mass spectra using D-brane actions, showing agreement with theoretical predictions and highlighting the importance of higher-loop corrections for complex states.

Contribution

It provides a detailed analysis of BPS mass spectra using D-brane effective actions and demonstrates how higher-loop effects are essential for matching U-duality predictions.

Findings

Mass spectrum of BPS states matches U-duality predictions.

Higher-loop corrections are necessary for intersecting D-branes.

The analysis confirms the role of SUSY cycles in BPS states.

Abstract

We give a confirmation of U-duality of type II superstring by discussing mass spectrum of the BPS states. We first evaluate the mass spectrum of BPS solitons with one kind of R-R charges. Our analysis is based on the 1-loop effective action of D-brane, which is known as ``Dirac-Born-Infeld (DBI) action'', and the fact that BPS states correspond to the SUSY cycles with minimal volumes. We show the mass formula derived in this manner is completely fitted with that given by U-duality. We further discuss the cases of BPS solitons possessing several kinds of R-R charges. These are cases of ``intersecting D-branes'', which cannot be described by simple DBI actions. We claim that, in these cases, higher loop corrections should be incorporated as binding energies between the branes. It is remarkable that the summation of the contributions from all loops reproduces the correct mass formula predicted by U-duality.