M. Baig

Fixed boundary conditions and phase transitions in pure gauge compact QED

Abstract We have simulated the pure gauge compact QED with fixed boundary conditions, on lattices from 6 4 to 16 4 . We argue that a lattice with this fixed boundary imposition corresponds actually to a lattice with spherical topology. We have found the presence of a phase transition without any trace of discontinuity. Moreover, the specific heat and the Binder cumulant are qualitatively consistent with a second order phase transition. The implications of this observation on the nature of the compact lattice QED are discussed.

The Lagrangian loop representation of lattice U(1) gauge theory

Abstract It is showed how the Hamiltonian lattice loop representation can be cast straighfforwardly in the Lagrangian formalism. The procedure is general and here we present the simplest case: pure compact QED. This connection has been shaded by the non canonical character of the algebra of the fundamental loop operators. The loops represent tubes of electric flux and can be considered the dual objects to the Nielsen-Olesen strings supported by the Higgs broken phase. The lattice loop classical action corresponding to the Villain form is proportional to the quadratic area of the loop world sheets and thus it is similar to the Nambu string action. This loop action is used in a Monte Carlo simulation and its appealing features are discussed.

Finite-size analysis of the 4D abelian surface gauge model

We present the results of a finite-size analysis of the four dimensional abelian surface gauge model. This model is defined assigning abelian variables to the plaquettes of an hypercubical lattice, and is dual to the four dimensional Ising model. This last model is known to present a second order phase transition with mean field critical exponents. We have performed Monte Carlo simulations on several lattice sizes and high statistics. The analysis of the partition function zeroes and the specific heat scaling behaviour allowed us to estimate the critical coupling

Monte Carlo analysis of non compact QED lattice theory with Higgs fields

beta_c

Monte Carlo and mean link analysis of the SU(2) ⊗ SU(2) chiral model in two dimensions with mixed action

as well as the critical exponents

Monte Carlo analysis of the Λ-parameter in an SU(2) lattice gauge theory with a mixed action

nu

f-pole corrections to the critical parameters of the pomeron

and

Fixed boundary conditions analysis of the 3d gonihedric Ising model with κ = 0

alpha

Matter fields in the Lagrangian loop representation: scalar QED

. Our results are consistent with the second order critical exponents

Specific heat measurements of the three-dimensional SO(3) I.Attice gauge theory

nu = 1/2