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Wednesday 17 May 2017, 11:00 at LPTHE, Bibliothèque  SEMINFOR (Séminaire informel)  hepthmathmathphmath.AGmath.COmath.KTmath.MPmath.QA 



Abstract:  Schubert calculus is a branch of enumerative geometry, which deals with configurations of linear subspaces of a vector space. Translated into the modern language, it amounts to certain calculations in the cohomology ring of Grassmannians and flag varieties. A practical problem is to give a combinatorial rule for the structure constants of that ring. A few years ago, I observed that there was a hidden quantum integrability in the case of Grassmannians (for which the combinatorial rule is the socalled LittlewoodRichardson rule). In a somewhat unrelated development, there has been a growing body of work (including my own) showing the deep connection between cohomology theories (ordinary cohomology, Ktheory, elliptic cohomology) and quantum integrable systems. In particular Maulik and Okounkov introduced a nice framework for this connection. It is natural to try to reinterpret my observation above in this language. After introducing these various concepts, I shall present recent work with A. Knutson in this direction. In particular, this provides completely new rules for the calculation of structure constants of the equivariant cohomology or Ktheory of dstep flag varieties for d smaller or equal to 4, thus moving several "steps" closer to the completion of the program of Schubert calculus. 
Wednesday 17 May 2017, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Thursday 18 May 2017, 13:30 at DPTPHYSENS, room Conf. IV, 24 Rue Lhomond, ENS Paris  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  condmat 


Friday 19 May 2017, 11:30 at SAMM, C20.13, Centre Pierre MendèsFrance, Univ. Paris1, 90 rue de Tolbiac, Paris  SAMM (Statistics, Analysis, Multidisciplinary Modeling)  condmat.statmechmath.PRmath.ST 



Abstract:  We construct an estimator of the Lévy density, with respect to the Lebesgue measure, of a pure jump Lévy process from high frequency observations. The main novelty of our result is that we directly estimate the Lévy density in cases where the process may present infinite activity. Moreover, we study the risk of the estimator with respect to $L_p$ loss functions, $1\leq p < \infty$ The main idea behind the estimation procedure that we propose is to use that "every infinitely divisible distribution is the limit of a sequence of compound Poisson distributions" and to take advantage of the fact that it is well known how to estimate the Lévy density of a compound Poisson process in the high frequency setting. We consider linear wavelet estimators and the performance of our procedure is studied in term of L_p loss functions. The results are illustrated with several examples. 
Tuesday 23 May 2017, 14:00 at LPTHE, LPTHE Library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 



Abstract:  I will review some recent developments of type II and heterotic superstring field theory. The approach I will follow is due to Ashoke Sen and based on the construction of the openclosed bosonic string field theory by Zwiebach. Particular attention will be devoted to the three main challenges faced by superstring field theory: inclusion of the Ramond sector, removal of spurious singularities due to the superconformal ghosts and definition of a prescription for the offshell amplitudes. The plan is the following: 1) motivations, divergences in (super)string theory and offshell amplitudes; 2) superstring field theory: gauge fixed and quantum action, construction of the Ramond sector 3) momentum representation of amplitudes, applications: unitarity, soft theorems 
Tuesday 23 May 2017, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Tuesday 23 May 2017, 16:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTHEP (Séminaire de physique des particules et de cosmologie)  hepph 



Abstract:  Upcoming cosmological experiments intend to exploit the large scale structure of the Universe to get a better understanding of the observed cosmic acceleration. By measuring the power spectrum, one can constrain the equation of state of dark energy, and galaxy surveys promise great improvement over the current constraints. Galaxy surveys can also be used to gather cosmological information beyond cosmic acceleration. For example, one can derive consistency relations that can relate the bispectrum to the power spectrum for example. Those relations are very robust, as they rely on only two assumptions: the equivalence principle and the gaussianity of initial conditions. They are thus expected to hold within the standard cosmological model. On the other hand, their potential violation can be used to put bound on theories that predict deviations from one of those two assumptions, which is what I will explore in this talk. 
Wednesday 24 May 2017, 11:00 at LPTHE, Bibliothèque  SEMINFOR (Séminaire informel)  hepthmathmathphmath.AGmath.COmath.KTmath.MPmath.QA 



Abstract:  Schubert calculus is a branch of enumerative geometry, which deals with configurations of linear subspaces of a vector space. Translated into the modern language, it amounts to certain calculations in the cohomology ring of Grassmannians and flag varieties. A practical problem is to give a combinatorial rule for the structure constants of that ring. A few years ago, I observed that there was a hidden quantum integrability in the case of Grassmannians (for which the combinatorial rule is the socalled LittlewoodRichardson rule). In a somewhat unrelated development, there has been a growing body of work (including my own) showing the deep connection between cohomology theories (ordinary cohomology, Ktheory, elliptic cohomology) and quantum integrable systems. In particular Maulik and Okounkov introduced a nice framework for this connection. It is natural to try to reinterpret my observation above in this language. After introducing these various concepts, I shall present recent work with A. Knutson in this direction. In particular, this provides completely new rules for the calculation of structure constants of the equivariant cohomology or Ktheory of dstep flag varieties for d smaller or equal to 4, thus moving several "steps" closer to the completion of the program of Schubert calculus. 
Thursday 1 June 2017, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 1 June 2017, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 1 June 2017, 13:30 at DPTPHYSENS, room Conf. IV, 24 Rue Lhomond, ENS Paris  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  physics.optics 


Friday 2 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 )  COURS (Cours)  condmatquantph 



Abstract:  (TBA)  
Attachments: 
Tuesday 6 June 2017, 13:30 at
DPTPHYSENS,
room Conf. IV, 24 Rue Lhomond, ENS Paris ( ¡¡ Please be aware of the unusual date: Tuesday !! )  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  condmat.mtrlsci 


Tuesday 6 June 2017, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Tuesday 6 June 2017, 14:00 at LPTHE, Library  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Friday 9 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 )  COURS (Cours)  condmatquantph 



Abstract:  (TBA)  
Attachments: 
Tuesday 13 June 2017, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Thursday 15 June 2017, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 15 June 2017, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 15 June 2017, 13:30 at DPTPHYSENS, room Conf. IV, 24 Rue Lhomond, ENS Paris  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  physics.medph 


Friday 16 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 )  COURS (Cours)  condmatquantph 



Abstract:  (TBA)  
Attachments: 
Tuesday 20 June 2017, 14:00 at APC, 483 A  Malevitch  APCTH (Seminar of the theory group of APC)  hepth 


Thursday 22 June 2017, 13:30 at DPTPHYSENS, room Conf. IV, 24 Rue Lhomond, ENS Paris  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  physics.optics 


Friday 23 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 )  COURS (Cours)  condmatquantph 



Abstract:  (TBA)  
Attachments: 
Tuesday 27 June 2017, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTSEM (Séminaire du IPHT)  physics 


Tuesday 27 June 2017, 14:00 at IPHT, Salle Claude Itzykson, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 


Thursday 29 June 2017, 13:30 at DPTPHYSENS, room Conf. IV, 24 Rue Lhomond, ENS Paris  SEMPHYSENS (Colloquium du Département de Physique de l'ENS)  hepth 


Friday 30 June 2017, 10:00 at
IPHT,
Salle Claude Itzykson, Bât. 774 ( https://courses.ipht.cnrs.fr/?q=fr/node/168 )  COURS (Cours)  condmatquantph 



Abstract:  (TBA)  
Attachments: 
Friday 7 July 2017, 13:30 at IPHT, Salle Claude Itzykson, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 


Thursday 21 September 2017, 13:30 at IPHT, Amphi Claude Bloch, Bât. 774  SOUTENTH (Soutenance de thèse)  physics 



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