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 26 September 2017, 16:30 at UPMC, Amphithéâtre Charpak  CPMC (Colloquium Pierre et Marie Curie)  astroph 



Abstract:  One of the most exciting developments in astronomy is the discovery of thousands of planets around stars other than our Sun. But how do these exoplanets form, and why are they so different from those in our own solar system? Which ingredients are available to build them? Thanks to powerful new telescopes, especially the Herschel Space Observatory and the Atacama Large Millimeter Array (ALMA), astronomers are starting to address these ageold questions scientifically. Stars and planets are born in the cold and tenuous clouds between the stars in the Milky Way, and ALMA allows us to zoom in on planetary construction zones for the first time. Water and a surprisingly rich variety of organic materials are found, including simple sugars. Can these prebiotic molecules end up on new planets and form the basis for life elsewhere in the universe?  
Attachments: 
Thursday 28 September 2017, 11:00 at LPTHE, Bibliothèque  SEMINFOR (Séminaire informel)  condmat.statmech 



Abstract:  It is fascinating that most manybody systems, if unperturbed, tend to relax towards thermal equilibrium. I will discuss a recent result showing that quantum equilibrium dynamics can be elevated to the rank of a universal (modelindependent) symmetry of Keldysh field theories. This fundamental symmetry imposes strong constraints on the equilibrium correlation functions. But more importantly, this allows to study nonequilibrium dynamics as symmetrybreaking processes, providing important clues on the sofar poorly understood production of entropy in quantum mechanical systems. 
Thursday 5 October 2017, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 5 October 2017, 11:00 at LPTHE, Bibliothèque  SEMLPTHE (Séminaire du LPTHE)  condmat.statmechhepthmathph 



Abstract:  Horn's (classical) problem deals with the following question: what can be said about the spectrum of eigenvalues of the sum C=A+B of two Hermitian matrices of given spectrum ? Curiously this problem is intimately related to the "quantum" problem : given two irreducible representations of SU(n), which irreps appear in their tensor product ? The support of the spectrum of C is well understood, after a long series of works from Weyl (1912) to Knutson and Tao (1999), and the classical problem is known to provide an asymptotic approach of the quantum one. Here I show how an explicit computation based on a wellknown matrix integral enables one to determine the probability distribution of the eigenvalues of C, and sheds some new light on the relation between the classical and quantum problems. 
Thursday 5 October 2017, 11:30 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



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