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SEMPARIS – Séminaires en région parisienne
http ://string.lpthe.jussieu.fr/semparis/
Séminaires à venir à LPTHE
Mardi 14 Fevrier 2017, 14 :00
LPTHE, Library
Particle Physics at LPTHE
Domaines : astro-ph—hep-ph
Titre : Searching for different Dark Matter candidates in the inner Galaxy
Orateur : Daniele Gaggero ( University of Amsterdam )
Résumé : In the first part of the talk I discuss a new way to constrain the presence of a population of primordial black holes (PBHs) in the inner Galaxy.
In fact, the first direct detection of a gravitational wave signal, announced by
the LIGO collaboration earlier this year, demonstrated the existence of black
holes of 30 solar masses, prompting the suggestion that these objects are
PBHs and account for all the Dark Matter (DM) in the universe. In order
to rule out this scenario, we model the accretion of gas on to a population
of massive PBHs in the Milky Way, and compare the predicted radio and
X-ray emission with observational data. We show that, under conservative
assumptions on the accretion process, the possibility that these objects can
account for all of the DM in the Milky Way is excluded at 4σ ; by a comparison with the VLA radio catalog at 1.4 GHz, and at more than 5σ ; by a
comparison with the NuSTAR X-ray catalog. In the second part of the talk, I
discuss another recent claim of DM detection : The gamma-ray GeV excess
from the inner Galaxy, possibly a case of WIMP annihilation. In particular,
I show the possibility that the excess is actually just due to a mis-modeling
of the astrophysical background, and is reabsorbed with a more careful assessment of the cosmic-ray source distribution in the inner Galaxy.
Mercredi 15 Fevrier 2017, 11 :00
LPTENS, bibliothèque du LPTENS
Séminaire Darboux - physique théorique et mathématiques
Domaines : hep-th
Titre : Feynman amplitudes and limits of height pairings
Orateur : Omid Amini ( ENS )
Résumé : I will formulate and discuss from a mathematical perspective some
problems and results which emerge from the idea of realizing Feynman amplitudes as the low-energy limit of string amplitudes, as suggested by Physicists.
This is joint work with S. Bloch, J. Burgos, and J. Fresan.
Jeudi 23 Fevrier 2017, 11 :45
IHP, Amphitheatre Darboux
Rencontres Théoriciennes
Domaines : hep-th
Titre : TBA
Orateur : Ben Craps ( Vrije Universiteit Brussel )
Mardi 28 Fevrier 2017, 14 :00
LPTHE, Library
Particle Physics at LPTHE
Domaines : hep-ph
Titre : TBA
Orateur : Enrico Bertuzzo ( Universidade de Sao Paulo, Brasil )
Jeudi 9 Mars 2017, 11 :00
LPTHE, Bibliothèque
Séminaire informel
Domaines : cond-mat.stat-mech
Titre : Ward and Belavin-Polyakov-Zamolodchikov (BPZ) identities for Liouville quantum field theory on the Riemann sphere
Orateur : Vincent Vargas ( DMA ENS )
Résumé : Though the CFT formalism of Belavin, Polyakov and Zamolodchikov (BPZ) is widespread in the physics literature, it remains a challenge for
mathematicians to make sense out of it. Liouville CFT (or quantum field
theory) is an important class of CFTs which can be seen as a random version of the theory of Riemann surfaces. In a recent work, we constructed
the correlation functions (and the random measures) of Liouville CFT in
the Feynman path formalism using probabilistic techniques. In this talk, I
will present a rigorous derivation of the so-called Ward and BPZ identities
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for Liouville CFT. These identities are the building blocks of the CFT formalism. In the context of Liouville CFT, they are the basis to compute the
correlations of the theory and to establish the correspondence between the
Feynman path formalism and the algebraic formalism based on the Virasoro
algebra. Based on joint works with F. David, A. Kupiainen and R. Rhodes.
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