From Twists and Shifts to L-R asymmetric D-branes

TL;DR

This paper explores non-geometric twists, asymmetric orbifolds, and exotic D-branes in Type II superstring models, highlighting new constructions with reduced moduli and detailed analysis of L-R asymmetric D-brane bound states and their supersymmetry properties.

Contribution

It introduces novel asymmetric orbifold constructions with minimal moduli and provides a detailed study of L-R asymmetric D-branes and their supersymmetric bound states in Type II superstrings.

Findings

Construction of Type IIB models with few or no moduli.

Identification of D-brane bound states with residual supersymmetry.

Analysis of open string excitations in asymmetric D-brane configurations.

Abstract

In the first part of the talk, we discuss non-geometric twists and shifts and briefly review asymmetric orbifolds and free fermion constructions. These allow us to build Type IIB models with N = 1_L + 1_R and N = 1_L + 0_R models having few or no moduli. We then consider unoriented projections of the former and (`exotic') D-branes in the latter. In the second part, devoted to L-R asymmetric D-branes, we review how extended supergravity vacua in D=4 can be embedded in Type II superstrings. We then identify bound states of D-branes with residual susy and non-trivial R-R couplings. We discuss the N = 6 = 2_L + 4_R case in detail and sketch other extended susy cases. Finally we describe the resulting open string excitations. We conclude with some speculations and possible interesting developments.