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Numerical Study of the mass spectrum in the O(3) sigma model with a theta term

Presenter: Bartolome Alles Salom — INFN Pisa

Bartolome Alles, Alessandro Papa

It has been conjectured that the mass spectrum of the O(3) non–linear σ model with a θ term may possess an excited state, which decays when θ is lowered from π below a critical value. Since the direct numerical investigation of the model is prevented by a sign problem, we try to infer some information on the mass spectrum at real θ by studying the model at imaginary θ via analytical continuation. A modified Swendsen–Wang cluster algorithm has been introduced to simulate the model with the θ term.