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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Tuesday 23 January 2018, 11:00 at IHES, Amphithéâtre Léon Motchane  MATHIHES (TBA)  hepth 



Abstract:  Séminaire Laurent Schwartz  EDP et applications 
Tuesday 23 January 2018, 14:00 at
IHES,
Amphithéâtre Léon Motchane ( Séminaire Laurent Schwartz  EDP et applications )  MATHIHES (TBA)  hepth 


Tuesday 23 January 2018, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 



Abstract:  In the next few years, we are going to probe the lowredshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy. A particularly useful description of dark energy is through the Effective Field Theory of Dark Energy, which assumes that dark energy is the Goldstone boson of broken time translations. Such a formalism makes it easy to ensure that predicted signatures are consistent with wellestablished principles of physics. Since most of the information resides at high wavenumbers, it is important to be able to make predictions at the highest wavenumber that is possible. The Effective Field Theory of LargeScale Structure (EFTofLSS) is a theoretical framework that has allowed us to make accurate predictions in the mildly nonlinear regime. In this talk, I will discuss both the EFTofLSS and the EFTofDE, including the extension of the EFTofLSS to include the non linear effects of Horndeskitype dark energy in the quasistatic limit. 
Tuesday 23 January 2018, 15:30 at
IHES,
Amphithéâtre Léon Motchane ( Séminaire Laurent Schwartz  EDP et applications )  MATHIHES (TBA)  hepth 


Tuesday 23 January 2018, 16:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  In this talk I will discuss which Effective Field Theories (EFTs) may arise from underlying microscopic theories that have a unitarity, analytic, and crossingsymmetric Smatrix. I will show various applications in particle phenomenology as well as in cosmology, including recent theoretical constraints on Galileons and Lorentzinvariant massive gravity theories. 
Tuesday 23 January 2018, 16:30 at UPMC, Amphithéâtre G. Charpak  Rezdechaussée  Patio 2233  CPMC (Colloquium Pierre et Marie Curie)  physics.aoph 



Abstract:  Le Groupe intergouvernemental d'experts sur l'évolution du climat (GIEC) a pour mandat de coordonner la rédaction de rapports sur l'état des connaissances scientifiques visàvis du changement climatique, ses impacts, et les options de réponse tant pour l'adaptation que pour l'atténuation. Pour la préparation des rapports, le GIEC fait appel au travail volontaire de centaines d'auteurs et de milliers de relecteurs. C'est un organisme scientifique unique, qui joue un rôle clé pour une évaluation critique de l'état des connaissances et de leurs limites, pour le partage des connaissances, et pour le renforcement d'approches interdisciplinaires des multiples dimensions du changement climatique. J'expliquerai comment s'articule l'échange entre les gouvernements et la communauté scientifique pour la préparation de ces rapports. J'expliquerai les différentes étapes de préparation et de sélection des auteurs des rapports et mettrai l'accent sur la manière de participer au processus de relecture. J'illustrerai l'évolution des connaissances visàvis des causes des changements observés, et dans la compréhension des risques associés à la montée du niveau des mers, et comment l'identification de verrous scientifiques peut stimuler de nouvelles voies de recherche. En mars 2018, le GIEC fêtera ses 30 ans, à Paris. Ce sera l'occasion de structurer une réflexion sur les relations entre science et société, visàvis du changement climatique, et s'interroger sur le futur des rapports d'évaluation du GIEC : quels besoins ? quelles méthodes ? quelles approches pour communiquer les conclusions ?  
Attachments: 
Tuesday 23 January 2018, 17:15 at DPTPHYSENS, room Jean Jaurès (29 rue d'Ulm)  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  condmat.soft 



Abstract:  Over the past twenty years, great progress has been made in our understanding of how granular matter flows, a topic of both basic and practical interest. A distinctive feature of granular flows is that they display a flow threshold and a maximal packing fraction, beyond which no permanent flow is possible (jamming transition). In this seminar, I will illustrate how physical phenomena at the particle level (fluid drag, colloidal forces, particle agitation) can profoundly affect the flow behavior of a mixture of grains and fluids close to the jamming transition. First, I will show that the shorttime response of a dense suspension under impact is entirely controlled by the coupling between transient effects (Reynolds dilatancy) and the fluid pressure. I will then discuss how the addition of shortrange repulsive forces between grains can conspire with friction to yield the dramatic shearthickening behavior displayed by some suspensions like cornstarch. Finally, I will show how the sensor of gravity of plants relies on intracellular microavalanches flowing in an active liquid. 
Wednesday 24 January 2018, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  Antibranes are the usual suspects of de Sitter model building in string theory. They have been extensively used in flux compactifications to uplift anti de Stitter vacua to metastable de Sitter minima. In this talk I will start by briefly reviewing some recent results on the (non)existence of antibrane solutions as the ones used in model building. Afterwards I will present a model for inflation based on a series of antibrane annihilation processes, which provides a concrete string theory realization of the unwinding inflation mechanism. I will argue that the model succeeds in providing a large field excursion for the inflaton while satisfying the constraints required to maintain a consistent effective field theory. 
Thursday 25 January 2018, 10:00 at
LPTHE,
IMPMC, salle 401, tour 2223, 4eme étage ( Beware, unusual location ! )  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  I will discuss a recent attempt at gaining a handle over turbulent behaviour of fluids by appealing to the gauge gravity duality in the limit where the number of dimensions becomes very large. We will see that in this limit the gauge gravity duality simplifies and that the dynamics of the system are encoded in the large d limit of the hydrodynamic equations of motion. 
Thursday 25 January 2018, 11:00 at IPN, Salle A201  IPNX (Séminaire commun de physique théorique des particules IPNCPHTX)  heplat 



Abstract:  The axial coupling of the nucleon, gA, is a simple but fundamental quantity in particle physics. While gA is very wellmeasured experimentally, its theoretical prediction has been a longstanding puzzle: the lattice determinations being systematically below the experimental value. If we want to understand nuclear physics from first principle, it is crucial to solve this puzzle. I will present our recent computation performed with CalLat (California Lattice) based on a FeynmanHellmann approach. Our result is in perfect agreement with the experimental value with an uncertainty of less than 2%. I will discuss the various sources of systematic errors and I will give the several ingredients that allow our determination to be significantly more precise than the previous lattice computations. 
Thursday 25 January 2018, 11:45 at
LPTHE,
IMPMC, salle 401, tour 2223, 4eme étage ( Beware, unusual location ! )  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  Twistor strings have undergone a renewal of interest since the discovery of the CachazoHe Yuan formalism for scattering amplitude in field theory in 2013. These formulae deeply challenge the way we think about scattering amplitudes in quantum field theory and are neatly explained by the socalled ambitwistor string, a cousin of the old twistor string. The existence of these remarkable formalisms, which I shall present during the talk, cried for a connection to good old string theory. The answer to this question is now understood: it relies on counterintuitive limits and crucially, the existence of a different quantization for string theory, which we called “twisted strings”. The first part of the talk will be concerned on making that connection to string theory clear. In the second part, I’ll report on recent results obtained with Eduardo Casali on the winding modes of these twisted strings. They give rise to new exotic target space theories, naively non unitary, but exhibiting features half way between string and field theory. In particular, they are Tduality symmetric. 
Friday 26 January 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/195 )  COURS (Cours)  math.AG 



Abstract:  Algebraic equations are widespread in mathematics and physics, and the geometry of their spaces of solutions can be complicated. In the case of an equation of two complex variables, the space of solutions is a Riemann surface. \par We will provide basic tools (going back to Riemann) for studying algebraic equations and describing the geometry of compact Riemann surfaces. \par We will consider a Riemann surface defined from the solution locus of a polynomial equation $P(x,y)=0$ in $\mathbb{C} \times \mathbb{C}$. We will study its topology and geometry, and learn how to integrate differential forms along closed contours. Then we will describe the moduli space of Riemann surfaces with a given topology: its dimension, topology, etc. \par We will introduce some of the many tools that have been invented since the time of Riemann for studying these objects. We will partly follow the Mumford Tata lectures, the Fay lectures, and the FarkasKra book. \\ \\ The plan is: \\  Compact Riemann surfaces, charts, atlas, toplogy. Meromorphic functions and oneforms. Theorems on poles and residues. Newton's polygon. \\  Integrals, periods, Abel map, Jacobian, divisors. Theta functions, prime form, fundamental form. Basis of cycles, homology and cohomology. \\  Moduli spaces of Riemann surfaces. DeligneMumford compactification, Chern classes, tautological ring. Kontsevich integral and KdV hierarchy. \\  If times permits: fiber bundles, Hitchin systems, link to integrable systems.  
Attachments: 
Friday 26 January 2018, 11:00 at LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmech 



Abstract:  In Liouville theory, we derive a partial differential equation for fivepoint correlation functions with one degenerate field $V_{b/2}$. From it, one obtains explicit finitedimensional integral representations in terms of elliptic thetafunctions for a class of fourpoint conformal blocks for arbitrary intermediate dimension and generic value of the central charge. The conformal bootstrap can then be investigated analytically. Introducing a Bäcklund transformation on the solutions of the partial differential equation, one can reach a large extended set of external dimensions of these conformal blocks. 
Monday 29 January 2018, 10:30 at IMPMC, Jussieu 2322, 4e, salle 401  SEMEXCEP (Séminaire exceptionel)  physics 



Abstract:  À partir de deux enquêtes sociologiques menées auprès de chercheur.e.s et d’enseignant.e.schercheur.e.s en STEM entre 2006 et 2016, nous aborderons les normes de réussite académique et leur aspect genré. Nous nous intéresserons particulièrement à l’impact de ces normes sur l’équilibre vie professionnelle/vie privée et sur les carrières des physiciens et physiciennes. Nous présenterons enfin les actions visant à favoriser les carrières des chercheur.e.s, expérimentées dans le cadre du projet européen TRIGGER et plus spécifiquement à l’université Paris Diderot à travers le Pôle Égalité FemmesHommes (PEFH). 
Tuesday 30 January 2018, 13:30 at LPTM, Maison internationale de la recherche, NeuvillesurOise.  SEMEXCEP (Séminaire exceptionel)  condmat.disnn 



Abstract:  Neural population made of inhibitory and excitatory units exhibit complex collective dynamics when they are organized according to suitable circuits. In particular, amplification and synchronization mechanisms may emerge as purely noise driven effects: These results disclose new perspectives in the design of neuromorphic circuits performing specific tasks, like, signal categorization and detection. 
Tuesday 30 January 2018, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 



Abstract:  Random matrices are ubiquitous in modern theoretical physics and provide insights on a wealth of phenomena, from the spectra of heavy nuclei to the theory of strong interactions or random two dimensional surfaces. The backbone of all the analytical results in matrix models is their 1/N expansion (where N is the size of the matrix). Despite early attempts in the '90, the generalization of this 1/N expansion to higher dimensional random tensor models has proven very challenging. This changed with the discovery of the 1/N expansion (originally for colored and subsequently for arbitrary invariant) tensor models in 2010. I this talk I will present a short introduction to the modern theory of random tensors and its connections to conformal field theory and random higher dimensional random geometry. 
Tuesday 30 January 2018, 14:30 at IHES, Amphithéâtre Léon Motchane  PTIHES (Séminaire de physique théorique de l'IHES)  hepth 



Abstract:  Different forms of the matrix CayleyHamilton identity in some quantum algebras will be presented. In particular, I plan consider the socalled braided Yangian  some generalization of Drinfeld Yangian  recently introduced in my joint work with D. Gurevich. A quantum counterpart of the DrinfeldSokolov reduction based on the CayleyHamilton identity will be discussed as well. 
Tuesday 30 January 2018, 16:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  The modern incarnation of the analytic Smatrix is a nonperturbative approach that consist in exploring the space of Smatrix elements consistent with unitarity, analyticity, crossing symmetry and some extra physical assumptions about the mass spectrum of particles. In this talk I will discuss my work in progress to extend the recent ideas of the Smatrix bootstrap to include unstable resonances. This extension is crucial in order to apply such program to realistic particle physics questions involving unstable bound states. The goal of the program I will discuss is to uncover the space of consistent Smatrices for Higgslike bosons. 
Thursday 1 February 2018, 11:30 at LPTENS, LPTENS Library  STRINT (Strings, integrability and beyond)  hepth 


Thursday 1 February 2018, 14:00 at LPTM, 4.13 St Martin II  SEMLPTMUCP (Seminaires du LPTM , Universite de Cergy Pontoise)  condmat 



Abstract:  TBA 
Thursday 1 February 2018, 14:30 at LPTENS, LPTENS Library  STRINT (Strings, integrability and beyond)  hepth 


Friday 2 February 2018, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/195 )  COURS (Cours)  math.AG 



Abstract:  Algebraic equations are widespread in mathematics and physics, and the geometry of their spaces of solutions can be complicated. In the case of an equation of two complex variables, the space of solutions is a Riemann surface. \par We will provide basic tools (going back to Riemann) for studying algebraic equations and describing the geometry of compact Riemann surfaces. \par We will consider a Riemann surface defined from the solution locus of a polynomial equation $P(x,y)=0$ in $\mathbb{C} \times \mathbb{C}$. We will study its topology and geometry, and learn how to integrate differential forms along closed contours. Then we will describe the moduli space of Riemann surfaces with a given topology: its dimension, topology, etc. \par We will introduce some of the many tools that have been invented since the time of Riemann for studying these objects. We will partly follow the Mumford Tata lectures, the Fay lectures, and the FarkasKra book. \\ \\ The plan is: \\  Compact Riemann surfaces, charts, atlas, toplogy. Meromorphic functions and oneforms. Theorems on poles and residues. Newton's polygon. \\  Integrals, periods, Abel map, Jacobian, divisors. Theta functions, prime form, fundamental form. Basis of cycles, homology and cohomology. \\  Moduli spaces of Riemann surfaces. DeligneMumford compactification, Chern classes, tautological ring. Kontsevich integral and KdV hierarchy. \\  If times permits: fiber bundles, Hitchin systems, link to integrable systems.  
Attachments: 
Friday 2 February 2018, 11:00 at LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmech 



Abstract:  At very high disorder a generic closed quantum systems becomes completely localized. I argue that this (may body) localization is preempted by a wide regime of nonergodic behavior that displays a number of unusual properties. A good system to study these effects are Josephson junction arrays in a somewhat unusual regime. The toy model of disordered many body systems that capture the physics of many body systems is provided by random regular graphs. I will sketch a simplified analytical theory of the nonergodic phase in this models, compare the results with the direct numerical simulations and summarize the conclusions relevant for physical many body systems. 
Monday 5 February 2018, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTPHM (Séminaire de physique mathématique)  mathph 



Abstract:  Circle patterns are one of the ways to uniformize graphs on surfaces, by embedding them in such a way that every face admits a circumcircle. In this talk I will describe a discretetime dynamical system on circle patterns with the combinatorics of the square grid, called Miquel dynamics. It is based on the classical Miquel's six circles theorem. I will present some properties of this dynamics which suggest its integrability. \\ \\ Partly joint work with Alexey Glutsyuk (CNRS, Ecole normale superieure de Lyon / Higher School of Economics). 
Tuesday 6 February 2018, 11:30 at LPTENS, LPTENS library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 



Abstract:  This talk is devoted to Berry phases that appear in unitary representations of asymptotic symmetry groups in general relativity. These phases arise when a coherent state is acted upon by symmetry transformations that trace a closed path in the group manifold, and they can be evaluated exactly even when the group is infinitedimensional. We apply these ideas to the Virasoro and BMS groups; seeing their representations as particles dressed with boundary gravitons, the associated Berry phases generalize Thomas precession and provide, in principle, observable signatures of asymptotic symmetries. 
Tuesday 6 February 2018, 16:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  The initial stage of inelastic high energy nuclear collisions is known as the Glasma, namely a configuration of strong chromoelectric and chromomagnetic fields which develop along the flight direction of the two colliding nuclei; the evolution of these fields eventually leads to the formation of the quarkgluon plasma. In this seminar I focus on the Glasma that can be produced in high energy protonproton collisions. The main goals are the study of isotropization, of gauge invariant correlation functions that allow us to understand the building up of color domains and the string breaking of the Glasma starting from the color strings, and of the distribution of the topological charge density which might be relevant for the chiral magnetic effect. 
Tuesday 6 February 2018, 17:15 at DPTPHYSENS, room Jean Jaurès (29 rue d'Ulm)  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  condmat.meshall 



Abstract:  When confining photons in semiconductor lattices, it is possible deeply modifying their physical properties. Photons can behave as finite or even infinite mass particles, photons can propagate along edge states without back scattering, photons can become superfluid, photons can behave as interacting particles. These are just a few examples of properties that can be imprinted into fluids of light in semiconductor lattices. Such manipulation of light present not only potential for applications in photonics, but great promise for fundamental studies. One can invent artificial media with very exotic physical properties at the single particle level or even more interestingly when many body interactions are considered. During the talk, I will illustrate the variety of physical systems we can emulate with fluids of light by presenting a few recent experiments. Perspectives in terms of quantum simulation will be discussed. 
Thursday 8 February 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 


Thursday 8 February 2018, 14:00 at LPTM, 4.13 St Martin II  SEMLPTMUCP (Seminaires du LPTM , Universite de Cergy Pontoise)  physics.optics 



Abstract:  We consider the propagation of a quantum light field in a cavityless nonlinear medium. In this alloptical platform, the space propagation of the field's envelope may be mapped onto the time evolution of a quantum fluid of interacting photons. The resulting manybody quantum system constitutes a particular class of quantum fluids of light and presently attracts a growing interest as a powerflul tool for quantum simulation. I will present recent theoretical and experimental progresses in this rapidly emerging research field, including investigations on superfluidity, elementary excitations, disorder, quantum quenches, prethermalization, thermalization, and BoseEinstein condensation. 
Thursday 8 February 2018, 16:30 at INSP, 2223 3ème étage pièce 317  SEMINSP (Séminaire général de l'INSP)  physicsphysics.aophphysics.genphphysics.medphphysics.socph 



Abstract:  Cet exposé se concentrera sur les particules de diamètres aérodynamiques inférieurs à 10 $\mu$m. La dynamique de ces particules sera décrite et illustrée par le nuage de cendres volcaniques ayant recouvert l’Europe en 2010 suite à l’éruption du volcan Eyjafjallajökull. Dans une deuxième partie, on verra que les particules fines se retrouvent dans la chaine alimentaire et comment on peut retracer l’histoire des explosions atmosphériques d’armes nucléaires et des accidents dans les centrales nucléaires à travers l’analyse de la radioactivité des millésimes des vins. La troisième partie sera consacrée à la pollution de l’air par les particules fines à « l’air libre » et dans un milieu clos : le métro parisien ; l’origine des polluants sera discutée. La dernière partie de l’exposé sera consacrée à l’effet des particules fines inhalées sur les êtres humains et discutera l’origine des particules « tueuses ». 

[ English version ] 