Andrea Pelissetto

Two-loop critical mass for Wilson fermions

We have redone a recent two-loop computation of the critical mass for Wilson fermions in lattice QCD by evaluating Feynman integrals with the coordinate-space method. We present the results for different types of infrared regularization. We confirm both the previous numerical estimates and the power of the coordinate-space method whenever high accuracy is needed.

Universal distance ratios for two-dimensonal self-avoiding walks: corrected conformal-invariance predictions

The authors correct a combinatorial error in the Cardy-Saleur conformal-invariance prediction of a universal amplitude ratio for two-dimensional self-avoiding walks. They present high-precision Monte Carlo data that confirm the corrected prediction.

Finite-Size Scaling in the Driven Lattice Gas

AbstractWe present a Monte Carlo study of the high-temperature phase of the two-dimensional driven lattice gas at infinite driving field. We define a finite-volume correlation length, verify that this definition has a good infinite-volume limit independent of the lattice geometry, and study its finite-size-scaling behavior. The results for the correlation length are in good agreement with the predictions based on the field theory proposed by Janssen, Schmittmann, Leung, and Cardy. The theoretical predictions for the susceptibility and the magnetization are also well verified. We show that the transverse Binder parameter vanishes at the critical point in all dimensions

Transverse Fluctuations in the Driven Lattice Gas

d \geqslant 2

NONPERTURBATIVE LATTICE GRAVITY

and discuss how such result should be expected in the theory of Janssen et al. in spite of the existence of a dangerously irrelevant operator. Our results confirm the Gaussian nature of the transverse excitations.

The restoration of poincaré invariance and the energy momentum tensor in lattice gauge theories

We study the nature of the two-dimensional quantum critical point separating two phases with and without long-range spin-density-wave order, which has been recently observed in cuprate superconductors. We consider the Landau-Ginzburg-Wilson Hamiltonian associated with the spin-density critical modes, perform a mean-field analysis of the phase diagram, and study the corresponding renormalization-group flow in two different perturbative schemes at five and six loops, respectively. The analysis supports the existence of a stable fixed point in the full theory whose basin of attraction includes systems with collinear spin-density-wave order, as observed in experiments. The stable fixed point is characterized by an enlarged O(4)xO(3) symmetry. The continuous transition observed in experiments is expected to belong to this universality class. The corresponding critical exponents are nu = 0.9(2) and eta = 0.15(10).

FROM LATTICE GAUGE THEORY TOWARDS GRAVITY

We define a transverse correlation length suitable to discuss the finite-size scaling behaviour of an out-of-equilibrium lattice gas, whose correlation functions decay algebraically with the distance. By numerical simulations we verify that this definition has a good infinite-volume limit independent of the lattice geometry. We study the transverse fluctuations as they can select the correct field-theoretical description. By means of a careful finite-size scaling analysis, without tunable parameters, we show that they are Gaussian, in agreement with the predictions of the field theory proposed by Janssen, Schmittmann, Leung and Cardy.

Critical behavior of two-dimensional fully frustrated XY systems

We discuss several examples of three-dimensional critical phenomena that can be described by Landau–Ginzburg–Wilson ϕ4 theories. We present an overview of field-theoretical results obtained from the analysis of high-order perturbative series in the frameworks of the ∊ and of the fixed-dimension d=3 expansions. In particular, we discuss the stability of the O(N)-symmetric fixed point in a generic N-component theory, the critical behaviors of randomly dilute Ising-like systems and frustrated spin systems with noncollinear order, and the multicritical behavior arising from the competition of two distinct types of ordering with symmetry O(n1) and O(n2) respectively.