Describing anti-branes in F-theory using Lefschetz fibrations

Abstract

Type IIB string theory turns out to be SL(2,Z) invariant. This allows us to translate setups in string theory containing 7-branes to geometric objects called elliptic fibrations. This program is called F-theory. However, we cannot translate anti-branes into this type of geometry. We present an alternative for elliptic fibrations called achiral Lefschetz fibrations. We show that these allow for the description of anti-branes in a very natural way and also allow for the basic properties that we want these anti-branes to have.