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TZID:Europe/Paris
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BEGIN:VEVENT
UID:1-510@lptms.universite-paris-saclay.fr
DTSTART:20170425T110000Z
DTEND:20170425T120000Z
DTSTAMP:20170407T095839Z
URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-du-lptm
 s-gregoire-misguich/
SUMMARY:Séminaire du LPTMS: Grégoire Misguich - LPTMS\, salle 201\, 2ème
  étage\, Bât 100\, Campus d'Orsay - 25 Avr 17 11:00
DESCRIPTION:Entanglement and Shannon entropies in low dimensional magnets\n
 Grégoire Misguich (IPhT\, CEA\, Saclay)\nThe entanglement (von Neumann) e
 ntropy is now routinely used by condensed-matter theorists as a tool to pr
 obe quantum many-body  systems\, since it often gives access to propertie
 s that are not easily visible using more conventional observables. I will 
 illustrate this using a few examples taken from the literature on 1D and 2
 D spin systems. I will then discuss a related but different entropy\, the 
 Shannon entropy\, which can also be used as a tool to probe many-body  sy
 stems. The Shannon entropy of a many-body state |ψ&gt\;  is defined by e
 xpanding the wave-function in some preferential configuration basis { |i&g
 t\; }. The projections of  |ψ&gt\; onto the basis states define a set of
  normalized probabilities p[i] = |&lt\;ψ|i&gt\;|2\, and these probabiliti
 es can used to define an associated Shannon entropy S = - Σi p[i]*log(p[i
 ]). This quantity measures hos 'localized" is |ψ&gt\;\, in the chosen bas
 is. While the entanglement entropy requires the choice of a specific subsy
 stem\, the Shannon entropies is basis-dependent but is defined for the sys
 tem as a whole. In this talk we discuss a few examples in 1D and 2D where 
 some universal information about the long-distance physics of the system c
 an be obtained by analyzing the scaling of S as a function of the system s
 ize. In particular\, we show that the spontaneous symmetry breaking of a c
 ontinuous symmetry (as in Néel-ordered antiferromagnets) leads in 2D to s
 ome universal logarithmic terms in the Shannon entropy\n\nReference:\n\n	G
 . Misguich\, V. Pasquier &amp\; M. Oshikawa\, Shannon-Rényi entropy for 
 Nambu-Goldstone modes in two dimensions\, preprint arXiv:1607.02465\n\n&nb
 sp\;
CATEGORIES:seminars
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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