Applied Maths Seminar: Berry -- Physics of nonhermitian degeneracies

Speaker: Sir Michael Berry, Physics Department, University of Bristol

Decoherence makes quantum evolution nonunitary, and such systems, where some freedoms
are ignored, can be described by nonhermitian hamiltonian operators.  These differ most
dramatically from hermitian operators in the neighbourhood of degeneracies.  Several
examples of non-hermitian degeneracy-dominated physical phenomena will be given, in
laser physics, atom optics, and crystal optics.