The helicity modulus in gauge field theories

We consider the 4d compact U(1) theory with Wilson action and characterize its phase diagram using the notion of electromagnetic flux, instead of the more usual magnetic monopole. Taking inspiration from the flux picture, we consider the helicity modulus (h.m.) for this theory, and show that it is an order parameter for the confinement deconfinement phase transition. We extend the definition of the h.m. to an Abelian projected Yang-Mills theory, and discuss its behavior in SU(2).Comment: talk given by Michele Vettorazzo at Lattice2003(topology

Measuring interface tensions in 4d SU(N) lattice gauge theories

We propose a new algorithm to compute the order-order interface tension in SU(N) lattice gauge theories. The algorithm is trivially generalizable to a variety of models, e.g., spin models. In the case N=3, via the perfect wetting hypothesis, we can estimate the order-disorder interface tension. In the case N=4, we study the ratio of dual k-tensions and find that it satisfies Casimir scaling down to T=1.2 T_c.Comment: Talk presented at Lattice2004(topology), Fermilab, June 21-26, 2004; 3 pages, 4 figures, 1 tabl

Finite temperature phase transition in the 4d compact U(1) lattice gauge theory

We study the phase diagram of the 4d compact U(1) gauge theory as a function of the number of Euclidean time slices. We use the helicity modulus as order parameter to probe the phase transitions. The order of the transition along the phase boundaries is studied and the possibility of a continuum limit is discussed. We present new, strong evidence that the T=0 bulk phase transition is first-order.Comment: 17 pages, 12 figures; added references and acknowledgement; version in pres

A cluster algorithm for Lattice Gauge Theories

A new algorithm for simulating compact U(1) lattice gauge theory in three dimensions is presented which is based on global changes in the configuration space. We show that this algorithm provides an effective way to extract partition functions at given external flux. As an application, we study numerically the finite temperature deconfinement phase transition.Comment: 4 pages, 2 figures. Talk given at the Conference on Computational Physics, Genova, Italy, Sept. 200

Electromagnetic fluxes, monopoles, and the order of the 4d compact U(1) phase transition

We consider the 4d compact U(1) gauge theory with extended action S=-beta sum_P cos theta_P -gamma sum_P cos 2 theta_P We give a full characterization of the phase diagram of this model using the notion of flux. The relation with the usual monopole picture is discussed. In analogy with the XY model we consider the helicity modulus \cite{Jose:1977gm} for this theory, and show that it is an order parameter. Analyzing the finite-size effects of the helicity modulus we conclude that the transition is first-order. The value of this order parameter is related to the renormalized coupling beta_R. We measure beta^c_R at the transition point and give a counterexample to its conjectured universal value \cite{Cardy:jg}.Comment: 39 pages and 25 figures. The determination of the renormalized coupling has been improved. To appear in Nuclear Physics