Browsing by Author "Grinza, Paolo"
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Item Decay of particles above threshold in Ising field theory with magnetic field(2005) Delfino, Gesualdo; Grinza, Paolo; Mussardo, Giuseppe; Mathematics; Mathematical PhysicsThe two-dimensional scaling Ising model in a magnetic field at critical temperature is integrable and possesses eight stable particles Ai (i = 1, . . . , 8) with different masses. The heaviest five lie above threshold and owe their stability to integrability. We use form factor perturbation theory to compute the decay widths of the first two particles above threshold when integrability is broken by a small deviation from the critical temperature. The lifetime ratio t4/t5 is found to be 0.233; the particle A5 decays at 47% in the channel A1A1 and for the remaining fraction in the channel A1A2. The increase of the lifetime with the mass, a feature which can be expected in two dimensions from phase space considerations, is in this model further enhanced by the dynamics.Item Potts correlators and the static three-quark potential(2005) Caselle, Michele; Delfino, Gesualdo; Grinza, Paolo; Jahn, O.; Magnoli, Nicodemo; Mathematics; Mathematical PhysicsWe discuss the two- and three-point correlators in the two-dimensional three-state Potts model in the high-temperature phase of the model. By using the form factor approach and perturbed conformal field theory methods we are able to describe both the large distance and the short distance behaviours of the correlators. We compare our predictions with a set of high precision Monte-Carlo simulations (performed on the triangular lattice realization of the model) finding a complete agreement in both regimes. In particular we use the two-point correlators to fix the various non-universal constants involved in the comparison (whose determination is one of the results of our analysis) and then use these constants to compare numerical results and theoretical predictions for the three-point correlator with no free parameter. Our results can be used to shed some light on the behaviour of the three-quark correlator in the confining phase of the (2+1)-dimensional SU(3) lattice gauge theory which is related by dimensional reduction to the three-spin correlator in the high-temperature phase of the three-state Potts model. The picture which emerges is that of a smooth crossover between a \Delta type law at short distances and a Y type law at large distances.