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SUMMARY:Branes\, strings and boojums\; topological defects in helium-3 and
  the cosmos - Haley\, R (Lancaster University)
DTSTART:20121205T135000Z
DTEND:20121205T141000Z
UID:TALK41861@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:The order parameter of the superfluid helium-3 condensate exhi
 bits broken symmetries that show analogs with those broken in the various 
 transitions undergone by the Universe after the Big Bang. Fortunately for 
 us\, the helium-3 order parameter is also sufficiently complex that the su
 perfluid may exist in several phases\, the two most stable being the A and
  B phases. At Lancaster we have developed techniques to investigate the pr
 operties of the interface between the A and B phases in the pure condensat
 e limit\, far below the superfluid transition temperature. The order param
 eter transforms continuously across the AB boundary\, making this interfac
 e the most coherent two-dimensional structure to which we have experimenta
 l access. It has been argued that this ordered 2-d surface in a 3-d bulk m
 atrix\, separating the two phases\, can provide a good analog of a cosmolo
 gical brane separating two distinct quantum vacuum states. In superfluid h
 elium-3 the creation of such 2-branes mu st lead to the formation of point
  and line defects in the texture of the 3-d bulk\, simply as a result of t
 he constraints imposed by the interplay of the order parameter symmetries 
 and the geometry of the container. Furthermore\, our experiments have show
 n that removing the 2-branes from the bulk\, in a process analogous to bra
 ne annihilation\, creates new line defects in large quantities. Such obser
 vations may provide insight into the formation of topological defects such
  as cosmic strings arising from brane interactions in the early Universe. 
 Up to now our experimental techniques have only allowed us to infer the pr
 operties of the interface and defects by measuring how they impede the tra
 nsport of quasiparticle excitations in the superfluid\, which is essential
 ly a remote measurement. Our new experiments allow us to directly probe th
 e interface region.\n
LOCATION:Seminar Room 1\, Newton Institute
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