Seminars



Monday, 19 November, 2018 - 14:30 - 15:30
Aula Grassano

Prof. Timo Weigand (CERN & Università di Heidelberg)

Title: A Stringy Test of the Weak Gravity Conjecture

Abstract: Various swampland conjectures have been put forward in the recent literature to characterize general properties of an effective field theory which can be consistently coupled to quantum gravity. String theory as a framework for quantum gravity allows us to put these conjectures to a quantitative test. Among the earliest of these conjectures is the Weak Gravity Conjecture: It postulates the existence of a set of particles in any quantum gauge theory coupled to gravity whose charge-to-mass ratio must exceed that of an extremal black hole. In this talk we will verify this and further swampland conjectures in string theory, focussing for simplicity on string compactifications to six dimensions with 8 supercharges, in the vicinity of the weak coupling point of the gauge theory. Our proof of the Weak Gravity Conjecture near the weak coupling point combines various aspects of the Kahler geometry of complex surfaces, arithmetic properties of weak Jacobi forms and BPS invariants on Calabi-Yau threefolds. Along the way we elucidate the modification of the Weak Gravity Conjecture due to massless scalar fields. We find perfect agreement between the predictions of the modified conjecture and the charge-to-mass ratio of a set of physical stringy non-BPS states in the theory. Their charges span a sublattice of the full charge lattice, whose index we determine geometrically.




Monday, 26 November, 2018 - 14:30 - 15:30
Aula Grassano

Dr. Yago Bea (University of Barcelona)

Title: Holographic collisions across a phase transition

Abstract: We use holography to mimic heavy ion collisions and obtain new qualitative insights possibly relevant for QCD. Our studies are motivated by the extensive experimental efforts devoted to the search of the conjectured critical point in the QCD phase diagram. Holographically, we perform collisions in strongly-coupled gauge theories with thermal phase transitions. We find that near a second order phase transition almost all the energy of the projectiles is deposited into a long-lived, quasi-static blob of energy. Moreover, hydrodynamics describes this blob only if we consider a formulation different from the Muller-Israel-Stewart formulation that is almost universally used in the numerical codes describing the quark-gluon plasma formed at RHIC and LHC.




Wednesday, 28 November, 2018 - 14:00 - 15:00
Aula Paoluzi

Prof. Georg Bergner (Friedrich-Schiller-Universität Jena - Germany)

Title: Supersymmetry on the lattice and non-perturbative properties of N = 1 supersymmetric Yang-Mills theory

Abstract: In this talk I briefly summarize the main obstacles in the formulation of supersymmetry on a space-time lattice and show how the fine tuning is resolved in the case of N=1 supersymmetric Yang-Mills theory. I will provide our most recent results for the bound state spectrum and the phase transitions of this theory obtained in numerical simulations.  I will also comment on our recent efforts to simulate supersymmetric QCD and other supersymmetric gauge theories.