Speaker: John Cardy (University of California, Berkeley, & All Souls College, Oxford)
Title: The TTbar deformation of 2d quantum field theory and modular forms
Abstract: "TTbar" deformed 2d quantum field theory is a non-local theory in which Minkowski space is deformed in a state-dependent but consistent manner. For a massive theory this is equivalent to each particle acquiring a width proportional to its mass in its rest frame, giving rise to simple CDD factors dressing the $S$--matrix, but for deformed conformal field theories the spectrum becomes quite complicated, and the question of modular invariance of the torus partition function is non-trivial.  I will show that this leads to a theory of TTbar deformed modular forms in general. Maass forms turn out to play an important role as eigenforms of the deformation.