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DTSTAMP:20260803T042827Z
LAST-MODIFIED:20121116T203436Z
DTSTART:20090402T150000Z
DTEND:20090402T160000Z
UID:event429@bu.edu
URL:http://physics.bu.edu/internal/events/show/429
SUMMARY:Entanglement Entropy at 2D quantum critical points and topological 
	fluids
DESCRIPTION:Featuring Eduardo Fradkin\, University of Illinois at Urbana-Ch
	ampaign\n\nPart of the Condensed Matter Theory Seminar Series.\n\nAbstract:
	 The entanglement entropy of a pure quantum state of a bipartite system is 
	defined as the von Neumann entropy of the reduced density matrix obtained b
	y tracing over one of the two parts. Critical ground states of local Hamilt
	onians in one dimension have entanglement that diverges logarithmically in 
	the subsystem size\, with a universal coefficient that is related to the ce
	ntral charge of the associated conformal field theory. In this talk I will 
	discuss the extension of these ideas to two dimensional systems\, either at
	 a special quantum critical point or in a topological phase. We find the en
	tanglement entropy for a standard class of z=2 quantum critical points in t
	wo spatial dimensions with scale invariant ground state wave functions: in 
	addition to a nonuniversal ``area law'' contribution proportional to the si
	ze of the boundary of the region under observation\, there is generically a
	 universal logarithmically divergent correction\, and in their absence a un
	iversal finite piece is found. This logarithmic term is completely determin
	ed by the geometry of the partition into subsystems and the central charge 
	of the field theory that describes the equal-time correlations of the criti
	cal wavefunction. On the other hand\, in a topological phase there is no su
	ch logarithmic term but instead a universal constant term. We will discuss 
	the connection between this universal entanglement entropy and the nature o
	f the topological phase. The application of these ideas to quantum dimer mo
	dels and fractional quantum Hall states will be discussed.
LOCATION:SCI 328\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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