Tuscan Meeting on Theoretical Physics (Joint INFN-SNS-UniFi-UniPi activity)

Friday, 27 February 2015 from to (Europe/Rome)
at Scuola Normale Superiore
11:00 - Thomas Hertog (K.U. Leuven)
Title: Towards a Quantum Theory of Lemaitre’s Primeval Atom.
Abstract: A central goal of quantum cosmology is to elucidate the physical conditions at the beginning, what Georges Lemaitre called the `primeval atom’ in 1931, in order to explain how the distinctive features of our universe emerged from the early quantum gravitational phase and why they are what they are. I sketch the overarching framework behind quantum cosmology, including recent developments aimed at making more explicit its predictions for our observations. I also discuss some of the outstanding challenges such as the important program to firmly root quantum cosmology in fundamental high-energy physics.
12:00 Lunch break
14:00 - Guido Festuccia (Niels Bohr Institute, Copenhagen)
Title: Twisted Holomorphic Theories and Supersymmetric partition functions.
Abstract: I will consider supersymmetric field theories on compact manifolds M and obtain constraints on the dependence of their partition functions Z_M on the geometry of M. For N=1 theories with a U(1) R symmetry in four dimensions, M must be a complex manifold with a Hermitian metric. I will show how describe the theory in terms of twisted variables that make easy to analyze the dependence of Z_M on the geometry of M and the parameters entering the Lagrangian. 
15:00 Coffee break
15:30 - Stephan Stieberger (Max Planck, Munich)
Title: New relations between gauge and gravity amplitudes in field and string theory.                     
Abstract: We exhibit new relations between gauge and gravity amplitudes in field and string theory. First, we establish a relation between open and closed string amplitudes communicated by some projection. As a consequence of the latter the alpha'-expansion of any closed string amplitude is dictated by that of the corresponding open string amplitude. Second, we show that the mixed gravitational/gauge amplitudes describing decays of gravitons or dilatons into a number of gauge bosons, can be written at the tree-level as linear combinations of pure gauge amplitudes in which the graviton (or dilaton) is replaced by a pair of collinear gauge bosons. We express N–graviton amplitudes in Einstein’s gravity as collinear limits of certain linear combinations of pure Yang-Mills amplitudes in which each graviton is represented by two gauge bosons, each of them carrying exactly one half of graviton’s momentum and helicity. Our results point into a deeper connection between gauge and gravity amplitudes than what is implied by the Kawai-Lewellen-Tye relations.

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