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  
[ scheduler view ] 
Tuesday 17 December 2019, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  The observed dark matter (DM) abundance in the Universe can be fully accounted for by a minimally coupled spectator scalar field that was light during cosmic inflation. In this scenario, dark matter was produced during inflation by amplification of quantum fluctuations of the spectator field. I will discuss the DM isocurvature perturbations that are unavoidably generated in such scenarios and the circumstances under which they are not problematic for the viability of nonthermal DM models. I will also discuss implications of DM isocurvature for structure formation, showing that the model has interesting consequences which allow one to test the scenario. 
Thursday 19 December 2019, 10:00 at IHP, Salle 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  I will prove a theorem about 2D CFTs: Every unitary 2D CFT must contain a nontrivial Virasoro primary of scaling dimension at most c/8 + 1/2, where c is the central charge. At large c, this is an improvement of the Hellerman bound c/6 + O(1), and is relevant for constraining the spectrum of gravitational theories in AdS3. The proof follows from the modular bootstrap and uses analytic extremal functionals, originally developed in the context of fourpoint SL(2) conformal bootstrap. In the second part of the talk, I will discuss a surprising connection between modular bootstrap and the spherepacking problem from discrete geometry. In particular, the above bound on the gap becomes a bound on the spherepacking density. In 8 and 24 dimensions, this bound is sharp and leads to a solution of the spherepacking problem in these dimensions, as originally proved by Viazovska et al. 
Thursday 9 January 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 9 January 2020, 11:40 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Friday 10 January 2020, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Thursday 16 January 2020, 11:00 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepthmath 



Abstract:  Classical genus zero proposes a duality phenomenon for CalabiYau (CY) manifolds, relating the Yukawa coupling for a large structure limit of CY's and enumerative invariants of rational curves on a mirror CY. For the higher genus counting problem, the corresponding conjectural program was proposed by BershadskyCecottiOoguriVafa (BCOV). In particular, they predict that a combination of holomorphic analytic torsions of large structure limits of CY's encapsulate genus one enumerative invariants on a mirror. In this talk I would like to present and discuss a refined conjecture which bypasses spectral theory and pertains to the realm of complex geometry, as for the Yukawa coupling. I will then explain a proof of this conjecture for the mirror family of CalabiYau hypersurfaces in projective space, which relies on the arithmetic RiemannRoch theorem in Arakelov geometry. The result is compatible with the BCOV predictions, as well as related work by Zinger. 
Friday 17 January 2020, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Thursday 23 January 2020, 10:00 at LPTHE, LPTHE Library  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 23 January 2020, 11:40 at LPTHE, bibliothèque du LPTHE, tour 1314, 4eme étage  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  (based on 1906.09228 ) 
Tuesday 28 January 2020, 11:30 at LPTHE, LPTHE library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Tuesday 4 February 2020, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 


Thursday 6 February 2020, 10:00 at LPTHE, LPTHE Library  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  TBA 
Thursday 6 February 2020, 11:40 at LPTHE, LPTHE Library  RENCTHEO (Rencontres Théoriciennes)  hepth 


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 12 March 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 23 April 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 14 May 2020, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 18 June 2020, 10:00 at IHP, 201  RENCTHEO (Rencontres Théoriciennes)  hepth 



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