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The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community.   [ More information ]


Upcoming Seminars at LPTHE
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Friday 16 November 2018, 11:00 at LPTHE, Bibliothèque SEM-LPTHE (Séminaire du LPTHE) cond-mat.stat-mech
Paola Ruggiero ( SISSA Trieste ) Conformal field theory on top of a breathing Tonks-Girardeau gas
Abstract: Conformal field theory (CFT) has been extremely successful in describing universal effects in critical one-dimensional (1D) systems, in situations in which the bulk is uniform. However, in many experimental contexts, such as quantum gases in trapping potentials and in several out-of-equilibrium situations, systems are strongly inhomogeneous. Recently it was shown that the CFT methods can be extended to deal with such 1D situations [1,2]: the system’s inhomogeneity gets reabsorbed in the parameters of the theory, such as the metric, resulting in a CFT in curved space. Here in particular we make use of CFT in curved spacetime to deal with the out-of-equilibrium situation generated by a frequency quench in a Tonks-Girardeau gas in a harmonic trap [3]. We show compatibility with known exact result and use this new method to compute new quantities, not explicitly known by means of other methods, such as the dynamical fermionic propagator and the one particle density matrix at different times. REFERENCES: [1] J. Dubail, JM. Stéphan, J. Viti, P. Calabrese, SciPost Phys. 2, 002 (2017). [2] S. Murciano, P. Ruggiero, P. Calabrese, To appear. [3] P. Ruggiero, Y. Brun, J. Dubail, To appear.

Friday 16 November 2018, 14:00 at LPTHE, Library LPTHE-PPH (Particle Physics at LPTHE) hep-ph
Avelino Vicente ( Valencia ) New physics in B-meson decays
Abstract: Current B-physics data contain two intriguing tensions. First, the LHCb collaboration has reported on some anomalies in b-s transitions, with discrepancies with the Standard Model predictions in some angular observables and branching ratios and intriguing hints for lepton universality violation. And second, BaBar, Belle and LHCb have found compatible deviations in observables associated to b-c transitions, again hinting at the violation of lepton universality. We will review the proposed explanations for these tensions and focus on new physics models that can simultaneously address both anomalies. In particular, we will discuss gauge extensions of the Standard Model aiming at such goal.

Thursday 22 November 2018, 10:00 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Ofer Aharony 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 1803.08529 )

Thursday 22 November 2018, 11:40 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
George Papadopoulos ( King's College, London ) Superconformal symmetry and classification of black hole horizons
Abstract: The horizon conjecture states that all near horizon geometries of extreme black holes that preserve some supersymmetry exhibit an sl(2, R) symmetry. I shall demonstrate the proof of the conjecture in some theories and use it to identify all the Killing superalgebras of near horizon geometries. An application of these results is that there are no near horizon geometries that preserve strictly more than 16 supesymmetries in 10 and 11 dimensions.

Thursday 29 November 2018, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) hep-th
Olivier Debarre ( DMA, ENS ) Variétés de Calabi-Yau et variétés hyperkählériennes
Abstract: Les variétés de Calabi-Yau sont les variétés complexes compactes kählériennes de dimension $n$ qui ont une $n$-forme holomorphe qui ne s'annule nulle part (la définition varie dans la littérature). Elles se répartissent en trois grandes catégories : les tores complexes, les variétés de Calabi-Yau « strictes », et les variétés hyperkählériennes, qui possèdent une 2-forme symplectique holomorphe. Ces dernières sont les plus rares. J'expliquerai quelques constructions connues. (based on 1607.08467 )

Thursday 13 December 2018, 11:00 at LPTHE, bibliothèque du LPTHE, tour 13-14, 4eme étage SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) hep-th
Eric Panzer ( Oxford ) TBA
Abstract: (based on 1607.08467 )

Friday 14 December 2018, 11:00 at LPTHE, Bibliothèque SEM-LPTHE (Séminaire du LPTHE) cond-mat.stat-mech|hep-th|math-ph
Blagoje Oblak ( ETH Zurich ) Stokes Drift as a Berry Phase
Abstract: In this talk I revisit Stokes drift in shallow water from a geometric perspective inspired by conformal field theory. Given a fluid on a circular pool supporting periodic waves, I argue that the displacement of fluid particles after one period involves a Berry phase associated with adiabatic conformal transformations. In particular, the phase shift produced by cnoidal waves can be evaluated in closed form, and matches the results of previous numerical estimates. Conceptually, this relates fluid dynamics, symplectic geometry, conformal field theory and Thomas precession.

Friday 18 January 2019, 11:00 at LPTHE, Bibliothèque SEM-LPTHE (Séminaire du LPTHE) cond-mat.stat-mech|hep-th|math-ph
Eoin Quinn ( LPTMS Orsay ) Organising strong correlations in electronic, spin, and local moment systems
Abstract: We present a framework for organising the correlations of interacting electrons, which provides access to a novel regime of strongly correlated behaviour. Following an introduction, we highlight two ways to characterise the electronic degree of freedom, either by the canonical fermion algebra or by the graded Lie algebra su(2|2). The first underlies Landau’s Fermi liquid description of correlated matter, and we identify an alternative Fermi liquid regime governed by the latter. We exploit the su(2|2) algebra to derive a systematic expansion of the electronic correlations, and describe the resulting leading approximations to electronic spectral function. These reveal a splitting in two of the electronic band, a violation of the Luttinger sum rule, and a Mott metal-insulator transition. We conclude with a reinterpretation of the meaning of the term ’strongly correlated’, and offer a scheme which encompasses magnetic, electronic, and local moment systems.

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