BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20261019T024259Z
LAST-MODIFIED:20170814T133931Z
DTSTART:20170816T150000Z
DTEND:20170816T160000Z
UID:event1783@bu.edu
URL:http://physics.bu.edu/internal/events/show/1783
SUMMARY:Entanglement entropy of finite-temperature pure quantum states and 
	thermodynamic entropy as a Noether  invariant
DESCRIPTION:Featuring Sho Sugiura\, University of Tokyo\nHosted by: Anatoli
	 Polkovnikov\n\nPart of the Condensed Matter Theory Seminar Series.\n\nEntr
	opy is a fundamental concept in statistical mechanics. In this talk\, I inv
	estigate two aspects of entropy. First\, we reveal a universal behavior of 
	entanglement entropy of the pure quantum states which are in thermal equili
	brium states. Second\, we characterize thermodynamic entropy as a Noether i
	nvariant under a non-uniform time translation. \n\nIn the first part\, we f
	ocus on the size dependence of the entanglement entropy of the pure quantum
	 states which can fully describe thermal equilibrium as long as one focuses
	 on local observables. The thermodynamic entropy can also be recovered as t
	he entanglement entropy of small subsystems. When the size of the subsystem
	 increases\, however\, quantum correlations break the correspondence and ma
	ndate a correction to this simple volume-law. The elucidatione of the size 
	dependence of the entanglement entropy is thus of essential importance in l
	inking quantum physics with thermodynamics\, and in analyzing recent experi
	ments on ultra-cold atoms. In this talk\, we derive an analytic formula of 
	the entanglement entropy for a class of pure states called cTPQ states repr
	esenting thermal equilibrium. We find that our formula applies universally 
	to any sufficiently scrambled pure state representing thermal equilibrium\,
	 i.e.\, general energy eigenstates of non-integrable models and states afte
	r quantum quenches. Our universal formula can be exploited as a diagnostic 
	tool for chaotic systems; we can distinguish integrable models from chaotic
	 modelsand detect many-body localization with high accuracy. \n\nIn the sec
	ond part\, we investigate a thermally isolated quantum many-body system wit
	h an external control represented by a time-dependent parameter. We formula
	te a path integral in terms of thermal pure states and derive an effective 
	action for trajectories in a thermodynamic state space\, where the entropy 
	appears with its conjugate variable. In particular\, for quasi-static opera
	tions\, the symmetry for the uniform translation of the conjugate variable 
	emerges in the path integral. This leads to the entropy as a Noether invari
	ant.
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR