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Seminars this week in series RENC-THEO
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Thursday 24 January 2019, 10:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4ème étage
( Attention, lieu inhabituel ! )
RENC-THEO (Rencontres Théoriciennes) hep-th
Ofer Aharony ( Weizmann Institute of Science, Rehovot ) Renormalization group flows in disordered field theories
Abstract: We will analyze the renormalization group (RG) flow of field theories with quenched disorder, in which the couplings vary randomly in space. We analyze both classical (Euclidean) disorder and quantum disorder, emphasizing general properties rather than specific cases. The RG flow of the disorder-averaged theories takes place in the space of their coupling constants and also in the space of distributions for the disordered couplings, and the two mix together. We write down a generalization of the Callan-Symanzik equation for the flow of disorder-averaged correlation functions. We find that local operators can mix with the response of the theory to local changes in the disorder distribution, and that the generalized Callan-Symanzik equation mixes the disorder averages of several different correlation functions. For classical disorder we show that this can lead to new types of anomalous dimensions and to logarithmic behavior at fixed points. For quantum disorder we find that the RG flow always generates a rescaling of time relative to space, which at a fixed point generically leads to Lifshitz scaling. The dynamical scaling exponent z behaves as an anomalous dimension and we compute it at leading order in perturbation theory in the disorder for a general theory. We also find in quantum disorder that local operators mix with non-local (in time) operators under the RG, and that there are critical exponents associated with the disorder distribution that have not previously been discussed. (based on 1803.08534 )

Thursday 24 January 2019, 11:40 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage
( Attention, lieu inhabituel ! )
RENC-THEO (Rencontres Théoriciennes) hep-th
Alessandro Tomasiello ( U. of Milano Bicocca ) De Sitter Solutions from Ten Dimensions
Abstract: Finding de Sitter compactifications of string theory has long been a challenge. They are known to require quantum corrections, or orientifold planes, or both. Most existing models rely on effective four-dimensional actions, or work with the ten-dimensional action but involve 'smearing' the internal O-planes. After a brief review of such efforts, we present some new numerical solutions with localized and back-reacted O8-planes. While the solution is singular and strongly-coupled near one of the O8s, it exhibits the same behavior observed for such objects in flat space and in a variety of AdS solutions in various dimensions, with solid holographic cross-checks. Away from the O8s the solution can be made parametrically weakly-coupled thanks to some moduli, whose nature might however be changed by string theory corrections.

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