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  [Next 30 ]  
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Thursday 18 October 2018, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepth 



Abstract:  On discutera de définir les fonctions de partition et de corrélation pour la théorie des champs de Liouville (dimension 2) sur les surfaces de genre $g\geq 2$. Celà permet de donner un sens mathématique aux théories de Polyakov sur les métriques aléatoires des surfaces (théorie des cordes bosoniques). On étudie en particulier le comportement au bord de l’espace des modules pour la fonction de partition et on montre que, couplée avec des champs de matière et les ghosts, la fonction de partition de Polyakov converge pour la charge centrale c=1. Travail en commun avec R. Rhodes et V. Vargas. (based on 1607.08467 ) 
Thursday 18 October 2018, 14:00 at CPHT, Salle de Conférence Louis Michel (Bât. 6)  SEMCPHT (Séminaire du CPHT)  hepth 



Abstract:  BirmanMurakamiWenzl (BMW) algebra was introduced in connection with knot theory. We treat here interaction round the face solvable (IRF) lattice models. We assume that the face transfer matrix obeys a cubic polynomial equation, which is called the three block case. We prove that the three block theories all obey the BMW algebra. This result is important to the solution of IRF lattice models and the development of new models, as well as to knot theory. (based on 1807.05603 ) 
Thursday 18 October 2018, 14:00 at IPHT, Amphi Claude Bloch, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 



Abstract:  Datasets come in a variety of forms and from a broad range of different applications. Typically, the observed data is noisy or in some other way subject to randomness. The recent developments in machine learning have revived the need for exact theoretical limits of probabilistic methods that recover information from noisy data. \par In this thesis we are concerned with the following two questions. \\ What is the asymptotically best achievable performance? \\ And how can this performance be achieved, i.e., what is the optimal algorithmic strategy? \par The above questions can be studied in a probabilistic framework, which leads to an average (i.e. typical) case answer. Such a probabilistic formulation is natural to statistical physics and leads to a formal analogy with problems in disordered systems. In turn, this permits to harvest the methods developed in the study of disordered systems, to attack constraint satisfaction and statistical inference problems. \par I will present four contributions. First, a statistical physics investigation of the circular coloring problem is carried out that reveals several distinct features. Second, new rigorous upper bounds on the size of minimal contagious sets in random graphs, with bounded maximum degree, are obtained. Third, the phase diagram of the dense DawidSkene model is derived by mapping the problem onto lowrank matrix factorization. The associated approximate message passing algorithm is evaluated on synthetic and realworld data. Finally, we propose an approach to derive the Bayes optimal denoising mean square error for a restricted class of extensive rank matrix estimation problems. 
Thursday 18 October 2018, 16:00 at LPT, 114  LPTPTH (Particle Theory Seminar of LPT Orsay)  hepph 



Abstract:  The recent intriguing measurements of $R_{K}$ and $R_{K^*}$ are important hints of new physics that violates lepton universality. We analyze the semileptonic decays $b \to s \ell^+ \ell^$ in the framework of the $BL$ extension of Minimal Supersymmetric Standard Model (MSSM) with Inverse Seesaw (BLSSMIS). A salient feature of this model is that one of the righthanded sneutrino can be light and the neutrino Yukawa couplings are of order one. We show that the box diagram mediated by righthanded sneutrino, higgsinolike chargino, and light stop can account simultaneously for both $R_{K}$ and $R_{K^*}$. Therefore, while the MSSM cannot explain the $R_K$ and $R_{K^*}$ anomalies, the BLSSMIS can account for them, where a significant lepton flavor nonuniversality might stem from large neutrino Yukawa couplings. 
Friday 19 October 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=en/node/220 )  COURS (Cours)  astrophgrqc 



Abstract:  The recent observation of gravitational wave signals from inspiralling and coalescing binary black holes has been significantly helped, from the theoretical side, by the availability of analytical results on the motion and gravitational radiation of binary systems. \par The course will deal with the Effective OneBody (EOB) theory of the motion and radiation of binary systems, and explain the links between this formalism and various classical and quantum approaches to gravitationally interacting twobody systems, from traditional postNewtonian computations of the effective twobody action to quantum gravitational scattering amplitudes. \par The following analytical techniques will be reviewed ab initio: \\ 1  Matched Asymptotic Expansions approach to the motion of black holes and neutron stars; \\ 2  postNewtonian theory of the motion of point particles; \\ 3  Multipolar postMinkowskian theory of the gravitational radiation of general sources; \\ 4  Effective OneBody (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of postNewtonianexpanded results. The postNewtonian approach assumes small gravitational potentials and small velocities, and loses its validity during the last orbits before the merger of black holes. The resummed EOB approach was able to extend the validity of the postNewtonian description of the motion and radiation of binary black holes to the strongfield, highvelocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate postNewtonianexpanded results on (slowmotion) bound states of gravitationally interacting binary systems into the (resummed) Hamiltonian of a particle moving in an effective external gravitational field. \par The second part of the course will present the recent extension of EOB theory to the description of (classical) scattering states within the postMinkowskian approach which does not assume that velocities are small. This led to new insights in the highenergy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some twoloop ultra highenergy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the highenergy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linearReggetrajectory behavior of highangularmomenta, highenergy circular orbits.  
Attachments: 
Friday 19 October 2018, 11:00 at LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmech 



Abstract:  Many classes of complex computational problems admit no efficient solution or even approximation, yet have a vast reach in applications across science and industry. From a physics perspective, computational complexity originates from correlations between bits of information. It is reasonable to ask whether computational approaches to quantum manybody problems can be practically useful in this context. In this talk, I will present newly found cases where the answer is affirmative. I will introduce constraint satisfaction problems (CSPs) and reformulate them as interacting models whose ground states represent the solution manifold. A procedure that reaches the ground states of these models implements a protocol of computation. In some protocols, the complexity that arises during computation can be viewed as quantum entanglement, and efficiency is achieved by controlling its growth. Using this reasoning, I will introduce practical methods for solving CSPs based on tensor network contraction and demonstrate that they outperform stateoftheart solvers for some of these problems by a significant margin. I will conclude with an outline of ongoing work on extensions and applications to problems of current interest, such as the simulation of existing and nearterm quantum circuits. 
Friday 19 October 2018, 14:00 at LPTHE, Library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  Conventional approaches to probing axions and axionlike particles (ALPs) typically rely on a coupling to photons. If this coupling is extremely weak, ALPs are effectively decoupled from the Standard Model. However, ALPs may also couple to the dark photon of a hidden sector U(1). We show that it is possible to probe such models via chiral gravitational waves sourced by an exponential production of the dark vector shortly after the ALP begins to oscillate. 
Friday 19 October 2018, 14:15 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=en/node/220 )  COURS (Cours)  astrophgrqc 



Abstract:  The recent observation of gravitational wave signals from inspiralling and coalescing binary black holes has been significantly helped, from the theoretical side, by the availability of analytical results on the motion and gravitational radiation of binary systems. \par The course will deal with the Effective OneBody (EOB) theory of the motion and radiation of binary systems, and explain the links between this formalism and various classical and quantum approaches to gravitationally interacting twobody systems, from traditional postNewtonian computations of the effective twobody action to quantum gravitational scattering amplitudes. \par The following analytical techniques will be reviewed ab initio: \\ 1  Matched Asymptotic Expansions approach to the motion of black holes and neutron stars; \\ 2  postNewtonian theory of the motion of point particles; \\ 3  Multipolar postMinkowskian theory of the gravitational radiation of general sources; \\ 4  Effective OneBody (EOB) theory of the motion and radiation of binary systems. \par The EOB formalism was initially based on a resummation of postNewtonianexpanded results. The postNewtonian approach assumes small gravitational potentials and small velocities, and loses its validity during the last orbits before the merger of black holes. The resummed EOB approach was able to extend the validity of the postNewtonian description of the motion and radiation of binary black holes to the strongfield, highvelocity regime reached during the last orbits, and the merger. EOB theory initially used a dictionary to translate postNewtonianexpanded results on (slowmotion) bound states of gravitationally interacting binary systems into the (resummed) Hamiltonian of a particle moving in an effective external gravitational field. \par The second part of the course will present the recent extension of EOB theory to the description of (classical) scattering states within the postMinkowskian approach which does not assume that velocities are small. This led to new insights in the highenergy limit of gravitational scattering and opened the way to transcribe quantum gravitational scattering amplitudes into their EOB Hamiltonian description. For instance, some twoloop ultra highenergy quantum scattering results of Amati, Ciafaloni and Veneziano could be transcribed into an improved knowledge of the highenergy limit of the classical gravitational interaction of two black holes. This leads also to interesting predictions about a linearReggetrajectory behavior of highangularmomenta, highenergy circular orbits.  
Attachments: 
Tuesday 23 October 2018, 10:30 at LPTHE, LPTHE library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 



Abstract:  The purpose of the talk is twofold. I will first report on progress made on the problem of finding a holographic dual of the large N=4 background AdS3xS3xS3xS1. I will discuss the BPS spectrum of the background in detail, both from a string theory and a supergravity point of view. This allows us to make a proposal for the CFT dual, at least for specific values of the fluxes. In a second part of the talk, I will discuss the string theory spectrum on AdS3 backgrounds away from the pure NSNS flux point, where a WZW description of the worldsheet theory exists. The theory with RR flux can be described in the hybrid formalism by a sigmamodel on a supergroup coupled to ghosts. I will explain how to solve this sigmamodel in the planewave limit and reproduce the planewave spectrum from the hybrid formalism. 
Tuesday 23 October 2018, 11:00 at LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  physics 



Abstract:  Understanding the statistical properties of the stationary points of highdimensional, random energy landscapes is a central problem in the physics of glassy systems, as well as in interdisciplinary applications to computer science, ecology and biology. In this talk, I will discuss a framework to perform the computation of the quenched complexity of stationary points, making use of a replicated version of the KacRice formula. I will discuss its application to simple models (the spiked tensor model and its generalizations) which capture the competition between a deterministic signal and stochastic noise, and correspond to a spherical pspin Hamiltonian endowed with ferromagnetic multibody interaction terms. I will describe the phase transitions that occur in the structure of the landscape when changing the signaltonoise ratio, and highlight the implications for the evolution of local dynamics within the landscape. Reference: Valentina Ros, Gerard Ben Arous, Giulio Biroli and Chiara Cammarota, Complex energy landscapes in spikedtensor and simple glassy models: ruggedness, arrangements of local minima and phase transitions, preprint condmat arXiv:1804.02686 
Tuesday 23 October 2018, 11:30 at LPTHE, LPTHE library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 



Abstract:  Recently a very interesting threedimensional N=2 supersymmetric theory with SU(3) global symmetry was discussed by several authors. The latter was conjectured to have two dual descriptions, one with explicit supersymmetry and emergent flavor symmetry and the other with explicit flavor symmetry and emergent supersymmetry. We discuss a third description of the model which has both flavor symmetry and supersymmetry manifest. We then investigate models which can be constructed by using this theory as a building block gauging the global symmetry and paying special attention to the global structure of the gauge group. We conjecture several cases of N=2 mirror dualities involving such constructions with the dual being either a simple N=2 WessZumino model or a discrete gauging thereof. 
Tuesday 23 October 2018, 14:00 at APC, 646 A  Mondrian  APCTH (Seminar of the theory group of APC)  hepth 



Abstract:  In this talk I will demonstrate how, by introducing additional scalar degrees of freedom, one can measure properties of the inflationary era which may be otherwise inaccessible. Using two explicit examples (the curvaton and a feebly interacting model of dark matter), which introduce new informative priors into the post inflationary phenomenology, we are able to constrain either the total duration that inflation takes place or its energy scale independently of the tensortoscalar ratio. Measurements of this kind may prove crucial in advancing the study of inflation if the future observational data were to yield a limited amount of new information. 
Tuesday 23 October 2018, 16:30 at UPMC, Amphi 24  Campus Pierre et Marie Curie  CPMC (Colloquium Pierre et Marie Curie)  nlin 



Abstract:  Water waves involve fluxes of momentum and energy that transport sediment along the shore. The flux toward shore of alongshore momentum depends on coastline orientation (relative to the wave propagation direction). Spatial variations in coastline orientation, therefore, are associated with gradients in alongshore sediment flux. Divergences in alongshore sediment flux cause coastline erosion, and convergences cause accretion. i.e., coastline shape determines the pattern of sediment fluxes that in turn change coastline shape. This ‘morphodynamic’ feedback can produce instabilities leading to the growth of largescale coastline features. In numerical experiments, finiteamplitude interactions then lead to a variety of coastline shapes, which are functions of wave climate (angular distribution). Changes in wave climate arising from changes in storm climate tend to reshape coastlines. In a case study, hindcasts of associated changes in shoreline erosion patterns are consistent with historical observations, opening up the possibility to forecast future coastal erosion ‘hot spots.’ However, on developed coastlines, couplings between human dynamics and coastline dynamics must be considered.  
Attachments: 
Wednesday 24 October 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Thursday 25 October 2018, 14:00 at LPTM, 4.13 St Martin II  SEMLPTMUCP (Seminaires du LPTM , Universite de Cergy Pontoise)  mathph 



Abstract:  Genuine highdimensional entanglement, i.e. the property of having a high Schmidt number, constitutes a resource in quantum processing protocols. On the contrary, states with a positive partial transpose (PPT) are generally considered weakly entangled, as they cannot be distilled into pure entangled states. This naturally raises the question whether high Schmidt numbers are possible for PPT states. This will be the main topic of the talk. I will begin with exhibiting an explicit construction of PPT state that achieves optimal Schmidt number scaling (in the dimension of the subsystems). I will then explain that, in fact, random PPT states typically share this feature. Finally I will study the somewhat opposite problem and show that the PPT property also imposes limitations on the Schmidt number. The talk will be based on arXiv:1802.04975. 
Thursday 25 October 2018, 16:00 at LPT, 114  LPTPTH (Particle Theory Seminar of LPT Orsay)  hepph 



Abstract:  Conventional approaches to probing axions and axionlike particles (ALPs) typically rely on a coupling to photons. If this coupling is extremely weak, ALPs are effectively decoupled from the Standard Model. However, ALPs may also couple to the dark photon of a hidden sector U(1). We show that it is possible to probe such models via chiral gravitational waves sourced by an exponential production of the dark vector shortly after the ALP begins to oscillate. 
Friday 26 October 2018, 11:00 at APC, 454A  APCCOLLOQUIUM (Colloquium de l'APC)  astroph 



Abstract:  TBA 
Friday 26 October 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  (TBA) 
Tuesday 30 October 2018, 11:00 at LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  physics 


Monday 5 November 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  I will show how hydrodynamic diffusion is generically present in manybody onedimensional interacting quantum and classical integrable models. I will extend the recently developed generalised hydrodynamic (GHD) to include terms of NavierStokes type which lead to positive entropy production and diffusive relaxation mechanisms. These terms provide the subleading diffusive corrections to Eulerscale GHD for the largescale nonequilibrium dynamics of integrable systems, and arise due to twobody scatterings among the quasiparticles of the model. Moreover I will show how with some particular choice of Hamiltonian interactions, the diffusion constant relative to the spin or charge degrees of freedom diverges, signaling the presence of super diffusive transport. 
Wednesday 7 November 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  (TBA) 
Friday 9 November 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Monday 12 November 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  CFT has been extremely successful in describing universal effects in critical onedimensional (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 outofequilibrium situations, systems are strongly inhomogeneous. Recently it was shown that the CFT methods can be extended to deal with such 1D situations: the systemâ€™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 outofequilibrium situation generated by a frequency quench in a TonksGirardeau gas in a harmonic trap. 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. StÃ©phan, J. Viti, P. Calabrese, SciPost Phys. 2, 002 (2017). [2] J. Dubail, JM. StÃ©phan, P. Calabrese, SciPost Phys. 3, 019 (2017). [3] P. Ruggiero, Y. Brun, J. Dubail, To appear. [4] S. Murciano, P. Ruggiero, P. Calabrese, To appear. 
Tuesday 13 November 2018, 11:00 at LPTMS, LPTMS, salle 201, 2ème étage, Bât 100, Campus d'Orsay  LPTMS (Séminaire du Laboratoire de Physique Théorique et Modèles Statistiques (Orsay))  physics 


Tuesday 13 November 2018, 14:00 at APC, 646 A  Mondrian  APCTH (Seminar of the theory group of APC)  hepth 


Wednesday 14 November 2018, 10:00 at
IHES,
Centre de conférences Marilyn et James Simons ( Séminaire de Géométrie Arithmétique ParisPékinTokyo )  MATHIHES (TBA)  hepth 



Abstract:  We give a new interpretation of Artin conductors of characters in the framework of theory of motives with modulus. It gives a unified way to understand Artin conductors of characters and irregularities of line bundle with integrable connections as well as overconvergent Fisocrystals of rank 1. It also gives rise to new conductors, for example, for Gtorsors with G a finite flat group scheme, which specializes to the classical Artin conductor in case G = Z/nZ. We also give a motivic proof of a theorem of Kato and Matsuda on the determination of Artin conductors along divisors on smooth schemes by its restrictions to curves. Its proof is based on a motivic version of a theorem of GabberKatz. This is a joint work with Kay Rülling. 
Wednesday 14 November 2018, 11:30 at
IPN,
Bâtiment 100, Salle A015 ( $ $ )  IPNTHEO (Séminaire du groupe de physique théorique de l'IPN Orsay)  nuclth 



Abstract:  The neutrinoless mode of double beta decay processes can shed light on the type of neutrino and on the conservation of the total lepton charge. Double electron capture (2EC) can give the same information about neutrino proper ties as double beta decay. The attempts of experimental observation of neu trinoless 2EC by detection of subsequent radiation of daughter nuclei are re viewed. To establish the resonance character of neutrinoless 2EC, knowledge of Q values and excitation energies of the atomic shell of daughter nuclei with two vacancies are required. The development of the Penning trap mass spec trometry made it possible to determine the mass differences of 14 promising nuclide pairs, connected via 2EC, with unprecedented low uncertainties. The energy of excited shells of atoms is determined from empirical data of Auger spectroscopy and/or by computer programs of quantum chemistry. A review of calculations of nuclear matrix elements for 2EC is given. Prospects for fur ther theoretical and experimental studies of neutrinoless 2EC are discussed.  
Attachments: 
Wednesday 14 November 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  (TBA) 
Thursday 15 November 2018, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepth 



Abstract:  (based on 1607.08467 ) 
Friday 16 November 2018, 11:00 at LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmech 



Abstract:  Conformal field theory (CFT) has been extremely successful in describing universal effects in critical onedimensional (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 outofequilibrium 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 outofequilibrium situation generated by a frequency quench in a TonksGirardeau 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. 

[ English version ] 