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BEGIN:VEVENT
UID:1-174@lptms.universite-paris-saclay.fr
DTSTART:20131008T110000Z
DTEND:20131008T120000Z
DTSTAMP:20131001T085716Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
 s-yasar-atas-et-francois-landes/
SUMMARY:Séminaire du LPTMS: Yasar Atas et François Landes - LPTMS\, salle
  201\, 2ème étage\, Bât 100\, Campus d'Orsay - 8 Oct 13 11:00
DESCRIPTION:Distribution of the ratio of level spacings in random matrix en
 sembles.\nYasar Atas\, LPTMS\nInitially introduced as a description of ene
 rgy levels of heavy atomic nuclei by Wigner\, Random Matrix Theory (RMT) i
 s nowadays an active field of theoretical physics with ramification in var
 ious disciplines such as number theory\, quantum chaos and finance to cite
  just a few. In RMT\, the distribution of level spacings plays a very impo
 rtant role: it has been widely used since the inception of the theory and 
 is considered as the "reference" measure of spectral statistics. Since dif
 ferent models may and do have different level densities\, one has to perfo
 rm a procedure on the spectrum called unfolding in order to obtain the spa
 cing distribution. This procedure is not unique and the choice of the unfo
 lding procedure is quite arbitrary. It seems then natural to search for an
 other measure which is independent of the level density. This has been don
 e quite recently by Oganesyan and Huse [1]: instead of looking at the spac
 ing they prefer to look at the ratio of two consecutive level spacings. Th
 is quantity has the advantage that it does not require any unfolding.\nIn 
 this talk\, I will make few remarks on random matrix theory and the unfold
 ing procedure. I will then derive simple expressions for the probability d
 istribution of the ratio of two consecutive spacings for the classical ens
 embles of random matrices [2]. These expressions\, which were lacking in t
 he literature\, will  be compared to numerical data from a quantum many-b
 ody lattice model and from zeros of Riemann zeta function.\n[1] V. Oganesy
 an and D. A. Huse\, Phys. Rev. B 75\, 155111 (2007). [2] Y. Y. Atas\, E. B
 ogomolny\, O. Giraud\, and G. Roux\, Phys. Rev. Lett. 110\, 084101 (2013)\
 n&nbsp\;\nAvalanche statistics in disordered visco-elastic interfaces\nFra
 nçois Landes\, LPTMS\nMany complex systems respond to a continuous input 
 of energy by an accumulation of stress over time\, and sudden energy relea
 ses\, called avalanches. Recently\, it has been pointed out that several b
 asic features of avalanche dynamics are induced at the microscopic level b
 y relaxation processes\, usually neglected by conventional models. I will 
 present a minimal model with relaxation and its mean field treatment\, and
  a quick snapshot of the finite dimension results. In mean-field\, our mod
 el yields a periodic behavior (with a new\, emerging time scale)\, with ev
 ents that span the whole system. In finite dimension (2D)\, the mean-field
  system-sized events become local\, and numerical simulations give qualita
 tive and quantitative results similar to the earthquakes observed in reali
 ty.
LOCATION:LPTMS\, salle 201\, 2ème étage\, Bât 100\, Campus d'Orsay\, 15 
 Rue Georges Clemenceau\, Orsay\, 91405\, France
GEO:48.698185;2.181768
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\,
  Orsay\, 91405\, France;X-APPLE-RADIUS=100;X-TITLE=LPTMS\, salle 201\, 2è
 me étage\, Bât 100\, Campus d'Orsay:geo:48.698185,2.181768
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