VII Tuscan Meeting on Theoretical Physics

Tuesday, 4 October 2016 from to (Europe/Rome)
at Scuola Normale Superiore ( Aula Bianchi )
Piazza dei Cavalieri, 7 Pisa
11:00 - Glenn Barnich (ULB, Brussels)
Title: Finite BMS transformations
Abstract: After a review of holographic features of general relativity in 3 and 4 dimensions, I will show how to derive the transformation laws of the Bondi mass and angular momentum aspects under finite supertranslations, superrotations and complex Weyl rescalings.
12:00 Lunch break
14:30 - Paul Townsend (DAMPT, Cambridge)
Title: Worldline time-reversal and a CPT anomaly
Abstract: The action for a massless particle in 4D Minkowski spacetime has a worldline time-reversing symmetry corresponding to CPT invariance of the quantum theory. The analogous symmetry of the N-extended superparticle is anomalous when N is odd; in the supertwistor formalism this is seen as a 1D analog of the 3D Parity anomaly. This result accords with the fact that there are no CPT self-conjugate massless N=1 supermultiplet. There is one when N is even, and it has 2**N states when N/2 is even but 2**(N+1) when N/2 is odd. From the perspective of worldline time-reversal invariance, this state doubling for odd N/2 is due to a Kramers degeneracy.
15:30 Coffee break
16:00 - Massimo Porrati (NYU, New York))
Title: Shaving off Black Hole Soft Hair
Abstract: After recalling the definition of black hole "hair" we explain why the only interesting hair are those that are also remnants. Next, we will examine a recent proposal by Hawking, Perry and Strominger, who suggest that soft photons and gravitons can be regarded as black hole hair that may be relevant to the black hole information paradox. We will make use of factorization theorems for infrared divergences of the S-matrix to argue that, by appropriately dressing in and out hard states, the soft-quanta-dependent part of the S-matrix becomes essentially trivial, in the sense that the information paradox can be fully formulated in terms of dressed hard states, which do not depend on soft quanta.

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