Non-trivial theta-vacuum effects in the 2-d O(3) model

by Uwe-Jens Wiese (Bern University)

Thursday 2 Aug 2012, 14:00 → 15:00 Europe/Zurich

4/2-011 - TH common room (CERN)

The 2-d O(3) model is investigated on the lattice as a function of the vacuum-angle theta. A simple but highly optimized lattice action ensures that cut-off effects are extremely small. Remarkably, dislocation lattice artifacts do not spoil the non-trivial continuum limit and there are different continuum theories for each value of theta. A precise study of the step scaling function confirms the conjectured exact S-matrix of the 2-d O(3) model at theta = pi, which represents a conformal fixed point. The essential features of walking technicolor models are shared by this toy model and are investigated in accurate numerical simulations of the slowly walking coupling and the resulting beta-function.