"F-theory vs Type IIB Orientifolds: Some global aspects"

ABSTRACT: F-theory marks a major step forward in the understanding of the strong coupling dynamics of type IIB superstrings. Using its M-theoretic definition, I will explicitly show how a global consistency check for string vacua, like the cancellation of Freed-Witten anomalies, generalizes to F-theory, affecting the quantization condition of the G-flux and imposing constraints on M5-instantons.Moreover, to assure a smooth type IIB orientifold background, I will propose a novel way of extracting a weakly coupled string description of F-theory, which has the advantage of avoiding the conifold singularities generically afflicting the traditional weak coupling limit of global SU(5) GUT models.