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SUMMARY:Quantum-classical mappings for geometrically frustrated systems - 
 Dr Stephen Powell\, University of Oxford
DTSTART:20080306T141500Z
DTEND:20080306T154500Z
UID:TALK9779@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:Several systems have recently been demonstrated to show "non-L
 GW" quantum phase transitions\, with different orderings on two sides of a
  continuous transition. We present two examples of classical statistical s
 ystems - spin ice in a [100] magnetic field [1] and an ordering transition
  of close-packed dimers on a cubic lattice - that appear to show continuou
 s (second-order) transitions that lie outside the Landau paradigm.\n\nIn b
 oth cases\, strong local constraints mean that neither of the neighbouring
  phases can be understood as thermally disordered\, excluding the standard
  route to a continuum critical theory. Instead\, we derive critical theori
 es for both transitions by mapping from three-dimensional classical proble
 ms to two-dimensional quantum problems. For the dimer model\, this mapping
  provides a direct connection to previous work [2] on non-LGW transitions 
 of lattice bosons at fractional filling factors.\n\n[1] L. Jaubert\, J. Ch
 alker\, P. Holdsworth\, and R. Moessner\; arXiv:0710.0976v1 [cond-mat.stat
 -mech]\n\n[2] L. Balents\, L. Bartosch\, A. Burkov\, S. Sachdev\, and K. S
 engupta\; Phys. Rev. B 71\, 144508 (2005) 
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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