Cecile, DJ; Chandrasekharan, S, *Absence of vortex condensation in a two dimensional fermionic XY model*,
Physical Review D - Particles, Fields, Gravitation, and Cosmology, vol. 77 no. 5
(2008),
pp. 054502 [e054502], [doi] .
**Abstract:**

*Motivated by a puzzle in the study of two-dimensional lattice quantum electrodynamics with staggered fermions, we construct a two-dimensional fermionic model with a global U(1) symmetry. Our model can be mapped into a model of closed packed dimers and plaquettes. Although the model has the same symmetries as the XY model, we show numerically that the model lacks the well-known Kosterlitz-Thouless phase transition. The model is always in the gapless phase showing the absence of a phase with vortex condensation. In other words the low energy physics is described by a noncompact U(1) field theory. We show that by introducing an even number of layers one can introduce vortex condensation within the model and thus also induce a Kosterlitz-Thouless transition. © 2008 The American Physical Society.*