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 ]
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Tuesday 11 February 2020, 11:00 at CPHT, Salle Louis Michel  SEMCPHT (Séminaire du CPHT)  hepth 


Wednesday 12 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  Higher Spin Gravities are supposed to be minimalistic extensions of gravity that embed it into a quantum consistent theory. However, such minimality turns out to be in tension with the field theory approach, as well as with the numerous nogo theorems. We report on the recent progress in constructing Higher Spin Gravities and testing quantum effects therein. The same time, via AdS/CFT Higher Spin Gravities should be related to a variety of interesting threedimensional CFT 
Tuesday 18 February 2020, 11:00 at CPHT, Salle Louis Michel, CPHT, Ecole Polytechnique  SEMCPHT (Séminaire du CPHT)  hepth 



Abstract:  I consider a model of fluid particle motion given by the reconstructed KdV equation on a circle. For travelling waves that are "uniformizable" in a suitable sense, the map that governs stroboscopic motion can be derived analytically. The particle's drift velocity, then, is essentially the Poincaré rotation number of that map, and has a geometric origin: it is the sum of a dynamical phase, a geometric/Berry phase, and an "anomalous phase". The last two phases are universal, as they follow entirely from the underlying Virasoro group structure. The Berry phase, in particular, is produced by a sequence of adiabatic conformal transformations due to the moving wave profile, and was previously found in twodimensional conformal field theories. 
Tuesday 18 February 2020, 17:15 at DPTPHYSENS, Amphi Jaurès  Département de Physique de l'ENS 24 rue Lhomond 75005 PARIS  COLLOQUIUMENS (Colloquium of the Physics Department of ENS)  physics 



Abstract:  Modeling fluid flows in channels is a general problem in science and engineering. For ideal liquids, the situation is simple: there is no dissipation due to fluid movement. For real liquids, some energy is lost. Navier, in his pioneering work on fluid mechanics identified two possible sources of dissipation: bulk dissipation, associated to the viscosity and the friction of the last layer of liquid molecules sliding on the solid surface. For surface dissipation, a classical assumption of fluid dynamics is that a liquid element adjacent to the surface is equal to the velocity of the surface, i.e. a nonslip boundary condition, which leads to no surface dissipation. This is not the only possibility. Navier, postulating the existence of a slip velocity at the surface, introduced the possibility of surface dissipation. He proposed a linear relation between the shear stress at the solidliquid interface and the slip velocity: σ=kV, where k is the interfacial friction coefficient. Indeed, it is also possible to define the slip length b as the distance from the solid surface where the fluid velocity profile extrapolates linearly to zero. During this presentation, I will briefly review what we know on the boundary condition for simple Newtonian liquids and show that polymers, due to their entanglements present a unique tool to study and understand the Navier condition. Based on a setup using the photobleaching of fluorescent polymers, I will present our last results on the slip of polymer melts and polymer solutions. 
Wednesday 19 February 2020, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 



Abstract:  I will first provide a birdeye view upon the infrared structure of gravity. I will shortly describe the relationship between BMS symmetry, soft theorems and memory effects at leading and subleading orders in the large radius expansion, while emphasizing the specificities of superLorentz symmetries. Secondly, I will present a nogo result on the soft hair conjecture: supertranslations induced by matter creating and falling inside black holes do not affect Hawking radiation, though they do affect scattering amplitudes. I will start by proving that Unruh radiation is unaffected by supertranslations induced by a shockwave and then show that Hawking radiation is mathematically related to this system, as a consequence of the principle of equivalence. Third, I will explain how BMS symmetry is associated to fluxbalance laws that provide constraints upon the motion of binary compact mergers. Finally, I will present the extension of the BMS group to asymptotically de Sitter spacetimes. 
Monday 24 February 2020, 10:30 at
LPTMC,
Jussieu tower 1312 5th floor room 523 ( Minilecture: three times 1.5 hours )  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  TBA 
Tuesday 25 February 2020, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  hepth 



Abstract:  Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained. Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as ominimal geometry, has for prototype real semialgebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity. The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on ominimal structures and their tameness properties, I will discuss:  the use of tame geometry in proving algebraization results (PilaWilkie theorem; ominimal Chow and GAGA theorems in definable complex analytic geometry);  the tameness of period maps; algebraicity of images of period maps;  functional transcendence results: AxSchanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (AndréOort conjecture and ZilberPink conjecture);  the geometry of Hodge loci and their closures. 
Wednesday 26 February 2020, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  hepth 



Abstract:  Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained. Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as ominimal geometry, has for prototype real semialgebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity. The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on ominimal structures and their tameness properties, I will discuss:  the use of tame geometry in proving algebraization results (PilaWilkie theorem; ominimal Chow and GAGA theorems in definable complex analytic geometry);  the tameness of period maps; algebraicity of images of period maps;  functional transcendence results: AxSchanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (AndréOort conjecture and ZilberPink conjecture);  the geometry of Hodge loci and their closures. 
Wednesday 26 February 2020, 12:00 at LPENS, Conf. IV  FORUMENS (Forum de Physique Statistique @ ENS)  condmat.statmech 


Thursday 27 February 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  TBA 
Thursday 27 February 2020, 13:30 at
LPTMC,
Jussieu tower 1312 5th floor room 523 ( Minilecture: three times 1.5 hours )  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  TBA 
Monday 2 March 2020, 11:00 at LPTMC, Jussieu tower 1312 5th floor room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  TBA 
Monday 2 March 2020, 11:30 at LPTENS, Scherk library (formerly LPTENS library)  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Monday 2 March 2020, 13:30 at LPENS, Conf IV  LPENSMDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)  condmat 



Abstract:  According to quantum mechanics, an electromagnetic mode without real photon excitations is nontrivial. It gives rise to vacuum electric field fluctuations. Despite averaging to zero over time, these fluctuations are responsible for the spontaneous emission, the Lamb shift and the Casimir effect. Using Landau polaritons, we demonstrate experimentally that the vacuum electric field acts on electron transport. The DC magneto resistance of the cavityembedded 2D electron gas is changed due to the coupling to vacuum. Intriguingly, our experimental platform allows to tune the vacuum mode insitu, while observing the response in the resistance. 
Tuesday 3 March 2020, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  hepth 



Abstract:  Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained. Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as ominimal geometry, has for prototype real semialgebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity. The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on ominimal structures and their tameness properties, I will discuss:  the use of tame geometry in proving algebraization results (PilaWilkie theorem; ominimal Chow and GAGA theorems in definable complex analytic geometry);  the tameness of period maps; algebraicity of images of period maps;  functional transcendence results: AxSchanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (AndréOort conjecture and ZilberPink conjecture);  the geometry of Hodge loci and their closures. 
Tuesday 3 March 2020, 11:00 at CPHT, Salle Louis Michel  SEMCPHT (Séminaire du CPHT)  hepth 



Abstract:  TBA 
Tuesday 3 March 2020, 17:15 at DPTPHYSENS, Conf IV (E244)  Département de Physique de l'ENS 24 rue Lhomond 75005 PARIS  COLLOQUIUMENS (Colloquium of the Physics Department of ENS)  physics 



Abstract:  Gravitational astronomy, which began on September 14th, 2015 with the LIGO detection of the merger of two black holes, has demonnstrated all its scientific potential during the 01 (LIGO) and 02 (LIGOVirgo) observation periods, between 2015 and 2017. At present, LIGO and Virgo are carrying out a third observation run, started on April 1st 2019, with the detection of a few gravitationalwave candidates per month. A program of detector upgrades, alternated with observation runs, will continue for most of the 2020 decade. After that period, a radical change of the detector infrastructure is necessary. The Einstein Telescope Europan project aims to continue the scientific program of Virgo and LIGO, with a detector having tenfold greater sensitivity than current instruments, 10 km arms, and an underground infrastructure. In this presentation, I will begin by introducing the scientific motivations for Einstein Telescope, then I will describe the planned technology and the implementation plans for the detector. 
Wednesday 4 March 2020, 10:30 at
IHES,
Amphithéâtre Léon Motchane ( Cours de l'IHES )  MATHIHES (TBA)  hepth 



Abstract:  Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained. Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as ominimal geometry, has for prototype real semialgebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity. The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on ominimal structures and their tameness properties, I will discuss:  the use of tame geometry in proving algebraization results (PilaWilkie theorem; ominimal Chow and GAGA theorems in definable complex analytic geometry);  the tameness of period maps; algebraicity of images of period maps;  functional transcendence results: AxSchanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (AndréOort conjecture and ZilberPink conjecture);  the geometry of Hodge loci and their closures. 
Thursday 5 March 2020, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  math.AG 



Abstract:  The theory of Bridgeland stability conditions has seen important developments in the past few years. Emerging from the mathematical physics literature, in particular in Douglas' work, it now connects to different branches in mathematics including symplectic geometry and representation theory. In this talk we will give a quick introduction to the basic theory of stability conditions for the derived category of coherent sheaves on a smooth projective variety, focusing on the recent advances in the threefold case; in particular, on the existence result for the quintic CalabiYau threefold. 
Thursday 5 March 2020, 13:30 at
LPTMC,
Jussieu tower 1312 5th floor room 523 ( Minilecture: three times 1.5 hours )  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 


Friday 6 March 2020, 11:00 at APC, Amphithéatre Pierre Gilles de Gennes  APCCOLLOQUIUM (Colloquium de l'APC)  astroph 


Tuesday 10 March 2020, 11:00 at IHP, Salle 314  P^3 (Particle Physics in Paris)  hepphhepth 


Wednesday 11 March 2020, 12:00 at LPENS, Conf. IV  FORUMENS (Forum de Physique Statistique @ ENS)  condmat.soft 


Wednesday 11 March 2020, 13:45 at LKB, ENS  Dept Phys  Conf IV  24, rue Lhomond  75005 Paris  SEMLKB (Séminaire du Laboratoire Kastler Brossel)  quantph 



Abstract:  Two dimensional materials provide new avenues for synthesizing compound quantum systems. Monolayers with vastly different electric, magnetic or optical properties can be combined in van der Waals heterostructures which ensure the emergence of new functionalities; arguably, the most spectacular example to date is the observation of strong correlations and low electron density superconductivity in moire superlattices obtained by stacking two monolayers with a finite twist angle. Optically active monolayers such as molybdenum diselenide provide a different "twist" as they allow for investigation of nonequilibrium dynamics in van der Waals heterostructures by means of femtosecond pumpprobe measurements. Moreover, interactions between electrons and the elementary optical excitations such as excitons or polaritons, provide an ideal platform for investigation of quantum impurity physics, with possibilities to probe both Fermi and Bosepolaron physics as well as mixtures with tunable density of degenerate fermions and bosons. After introducing the framework we use to describe manybody optical excitations in van der Waals heterostructures, I will describe two recent developments in the field. The first experiment uses pumpprobe measurements to demonstrate how excitonelectron interactions lead to strong enhancement of polaritonpolariton interactions, as well as to optical gain by stimulated cooling of excitonpolaronpolaritons. The second experiment shows that a tri layer system, consisting of two semiconducting monolayers separated by an insulating layer, provides an exciting platform for investigating strongly correlated electronic states in moire superlattices using optical spectroscopy. 
Thursday 12 March 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Friday 13 March 2020, 11:00 at APC, Amphithéatre Pierre Gilles de Gennes  APCCOLLOQUIUM (Colloquium de l'APC)  astroph 


Friday 13 March 2020, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Monday 16 March 2020, 13:30 at LPENS, Conf IV  LPENSMDQ (Séminaire Matériaux et Dispositifs Quantiques du LPENS)  condmat 



Abstract:  TBA 
Tuesday 17 March 2020, 11:00 at LPTHE, LPTHE library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Tuesday 17 March 2020, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  SEMEXCEP (Séminaire exceptionel)  physics 



Abstract:  (TBA) 

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