Phase structure of Abelian Chern-Simons gauge theories

We study the effect of a Chern-Simons (CS) term in the phase structure of two different Abelian gauge theories. For the compact Maxwell-Chern-Simons theory, we obtain that for values $g=n/2\pi$ of the CS coupling with $n=\pm 1,\pm 2$, the theory is equivalent to a gas of closed loops with contact interaction, exhibiting a phase transition in the $3dXY$ universality class. We also employ Monte Carlo simulations to study the noncompact U(1) Abelian Higgs model with a CS term. Finite size scaling of the third moment of the action yields critical exponents $\alpha$ and $\nu$ that vary continuously with the strength of the CS term, and a comparison with available analytical results is made.Comment: RevTex4, 4 pages, 1 figure; v3: improvements and corrections made in the first part of the paper; references added. To be published in Europhysics Letter

Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials

Compact abelian gauge theories in $d=2+1$ dimensions arise often as an effective field-theoretic description of models of quantum insulators. In this paper we review some recent results about the compact abelian Higgs model in $d=2+1$ in that context.Comment: 5 pages, 3 figures; based on talk by F.S. Nogueira in the Aachen HEP2003 conferenc

Ground State of the Hydrogen Atom via Dirac Equation in a Minimal Length Scenario

In this work we calculate the correction to the ground state energy of the hydrogen atom due to contributions arising from the presence of a minimal length. The minimal length scenario is introduced by means of modifying the Dirac equation through a deformed Heisenberg algebra (kempf algebra). With the introduction of the Coulomb potential in the new Dirac energy operator, we calculate the energy shift of the ground state of the hydrogen atom in first order of the parameter related to the minimal length via perturbation theory.Comment: 11 page

Solving the three-body bound-state Bethe-Salpeter equation in Minkowski space

The scalar three-body Bethe-Salpeter equation, with zero-range interaction, is solved in Minkowski space by direct integration of the four-dimensional integral equation. The singularities appearing in the propagators are treated properly by standard analytical and numerical methods, without relying on any ansatz or assumption. The results for the binding energies and transverse amplitudes are compared with the results computed in Euclidean space. A fair agreement between the calculations is found.Comment: 10 pages, 2 figures, version accepted for publication in Phys. Lett.