Sém. GPP : Etienne Granet (ENS Paris, CEA Saclay) : A study of a non-unitary statistical model : super spin chains and intersecting loops

Wednesday 7 Nov 2018, 15:00 → 17:00 Europe/Brussels

CYCL 04 (MdeHemptinne)

We study a non-unitary spin chain with orthosymplectic symmetry that generalizes the O(N) model to any positive or negative integer N. The lack of unitarity allows a stable massless Goldstone phase to appear, otherwise forbidden by the Mermin-Wagner theorem, that is described by a supersphere sigma model. On the 2D lattice it is represented as a dense loop model with loop weight N in which crossings are allowed. Unlike the usual O(N) loop model, the presence of crossings makes the model flow to a different regime where correlations involve logarithms. We compute these logarithmic critical exponents with field theory and the Bethe ansatz.