Triangle Seminars

Abstract:
In these lectures, I will introduce the concept of integrability and study its realisation in the context of gauge theory and string theory. In particular, I plan to review recent progress in computing the spectrum of operator dimensions in N=4 supersymmetric Yang-Mills theory and the dual problem of determining the spectrum of string theory on AdS5 x S5.

Abstract:
An atom exposed to an intense laser field may loose one or several of its electrons by photoionization. The field effectively turns all bound states into resonances of finite lifetime. For fields of constant intensity, this process is amenable to a time-independent description based on the method of complex scaling and on the Floquet theory of differential equations with periodic coefficients. The ionization rate of the state and the position of multiphoton resonances between Stark-shifted states can then be inferred from the spectrum of complex quasienergies of the Hamiltonian. After a general introduction to this approach, the talk will concentrate on a recent study of the origin of the sharp enhancements of emission of fast photoelectrons at certain intensities found a few years ago in the ionization of rare gases.

Abstract:
Negative curvature Euclidean (Hyperbolic) spaces have already been used in literature as part of eleven dimensional supergravity solutions. In particular it has been shown that they naturally appear when building expanding cosmological models. In this talk I will present M-theory solutions written as direct products of maximally symmetric spaces with hyperbolic components. These backgrounds break supersymmetry because of global effects but are still stable with respect to small scalar perturbations. They appear as near-horizon geometries for wrapped M5-branes, thus allowing for an intuitive interpretation of their stability.