"Symmetry breaking in smectics and surface models of their singularities"Gareth Alexander , University of Pennsylvania [Host: Andrew James]
ABSTRACT:
The homotopy theory of topological defects in ordered media fails to completely characterize systems with broken translational symmetry. We argue that the problem can be understood in terms of the lack of rotational Goldstone modes in such systems and provide an alternate approach that correctly accounts for the interaction between translations and rotations. Dislocations are associated, as usual, with branch points in a phase field, whereas disclinations arise as critical points and singularities in the phase field. We introduce a threedimensional model for twodimensional smectics that clarifies the topology of disclinations and geometrically captures known results without the need to add compatibility conditions. Our work suggests natural generalizations of the twodimensional smectic theory to higher dimensions and to crystals.

Condensed Matter Seminar Thursday, March 25, 2010 4:00 PM Physics Building, Room 204 Note special time. Note special room. 
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