BPS States with Extra Supersymmetry

TL;DR

This work investigates whether BPS states can preserve exotic fractions of supersymmetry beyond the familiar halves by analyzing the structure of central charges in the SUSY algebra. By examining both four-dimensional extended superalgebras and the eleven-dimensional M-theory algebra, it constructs simple charge configurations that could realize $3/4$ supersymmetry and discusses how dualities map these constructions to diverse brane intersections in string theory. It also explores tachyon condensation as a potential energy-lowering mechanism that could enable such exotic BPS states, while highlighting the lack of explicit classical $3/4$-SUSY solutions in $D=11$ supergravity and in the Wess–Zumino model. The findings clarify the conditions under which exotic fractions might arise and motivate further search for explicit realizations or fundamental constraints that prohibit them.

Abstract

A state saturating a BPS bound derived from a supersymmetry algebra preserves some fraction of the supersymmetry. This fraction of supersymmetry depends on the charges carried by the system, and we show that in general there are configurations of charges for which a BPS state would preserve more than half the original supersymmetry. We investigate configurations that could preserve 3/4 supersymmetry in string theory, M-theory and supersymmetric field theories and discuss whether states saturating these bounds actually occur in these theories.