Mesons at finite baryon density in (2+1)d

We discuss the critical properies of the three-dimensional Gross-Neveu model at nonzero temperature and nonzero chemical potential. We also present numerical and analytical results for the in-medium interaction due to scalar meson exchange. Further, we discuss in-medium modifications of mesonic dispersion relations and wavefunctions.Comment: 9 pages, 5 figures, Contribution to Workshop on Finite Density QCD at Nara, Japan, July 10-12 200

Universality in fermionic field theories at finite temperature

We discuss the critical properties of the three-dimensional NJL model at nonzero temperature. We show that the Z(2)-symmetric model undergoes a second order phase transition with 2d Ising exponents and its critical region is suppressed by a factor 1/N^{-0.5}. We also provide numerical evidence that the U(1)-symmetric model undergoes a BKT transition in accordance with the dimensional reduction scenario.Comment: 5 pages, Contribution to Conference on Strong and Electroweak Matter (SEWM2002), Heidelberg, Germany, 2-5 Oct. 200

Quantum Critical Behaviour in a Graphene-like Model

We present the first results of numerical simulations of a 2+1 dimensional fermion field theory based on a recent proposal for a model of graphene, consisting of N_f four-component Dirac fermions moving in the plane and interacting via an instantaneous Coulomb interaction. In the strong-coupling limit we identify a critical number of flavors N_fc=4.8(2) separating an insulating from a conducting phase. This transition corresponds to the location of a quantum critical point, and we use a fit to the equation of state for the chiral order parameter to estimate the critical exponents. Next we simulate N_f=2 corresponding to real graphene, and approximately locate a transition from strong to weak coupling behaviour. Strong correlations are evident in the weak-coupling regime.Comment: 14 pages, 6 figure