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SUMMARY:Vortex lines\, loop models\, and SU(n) magnets - Adam Nahum\, Univ
 ersity of Oxford
DTSTART:20120531T131500Z
DTEND:20120531T144500Z
UID:TALK37320@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:Vortex lines are a feature of many random or disordered three-
 dimensional systems (e.g. the 3D XY model). They show continuous percolati
 on-like phase transitions\, separating phases with only short vortex loops
  from phases with infinite vortex lines. This talk will begin with the pro
 blem of constructing a field theory for such transitions. This will lead u
 s to the replica limit n-->1 of the CP^{n-1} sigma model\, which at n>1 de
 scribes (2+1)-dimensional quantum antiferromagnets with SU(n) symmetry. I 
 will then discuss a class of 3D loop models which (as well as being intere
 sting polymer-like problems in their own right) provide a unifying descrip
 tion for line defects and SU(n) magnets\, and an ideal platform for Monte 
 Carlo simulations. I will describe our numerical results on such models\, 
 including preliminary results for the the 'deconfined' critical point much
  discussed in relation to the spin-1/2 square lattice antiferromagnet.\n\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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