Two Color Matter in the Quenched Approximation

We study a quenched SU(2) lattice gauge theory in 4d in which the spatial gauge ensemble $\{U_i\}$ is generated from a 3d gauge-Higgs model and the timelike link variables are ``reconstructed'' from the Higgs fields. The resulting ensemble is used to study quenched quark propagation with non-zero chemical potential $\mu$. While it proves possible to alter the strength of the inter-quark interaction by changing the parameters of the dimensionally reduced model, there is no evidence for any region of parameter space where quarks exhibit deconfined behaviour or thermodynamic observables scale as if there were a Fermi surface.Comment: 7 pages, 4 figures; Poster presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, German

Localised distributions and criteria for correctness in complex Langevin dynamics

Complex Langevin dynamics can solve the sign problem appearing in numerical simulations of theories with a complex action. In order to justify the procedure, it is important to understand the properties of the real and positive distribution, which is effectively sampled during the stochastic process. In the context of a simple model, we study this distribution by solving the Fokker-Planck equation as well as by brute force and relate the results to the recently derived criteria for correctness. We demonstrate analytically that it is possible that the distribution has support in a strip in the complexified configuration space only, in which case correct results are expected.Comment: 32 pages, many eps figure

Localised distributions in complex Langevin dynamics

Complex Langevin dynamics can be used to perform numerical simulations of theories with a complex action. In order to justify the procedure, it is important to understand the properties of the real and positive distribution, which is effectively sampled during the stochastic process. In the context of a simple model, we study this distribution and relate the results to the recently derived criteria for correctness. We demonstrate analytically that if the distribution has support only on a strip in the complexified configuration space, correct results are expected.Comment: 7 pages, 8 figures, talk given at the 31st International Symposium on Lattice Field Theory (Lattice 2013), July 29-August 3 2013, Mainz, German

On the conformal anomaly of k-strings

We discuss the long distance behaviour of the flux tube associated to baryon vertices and argue that, if the gauge system admits stable k-strings, the conformal field theory describing this string in the IR has conformal anomaly c=(d-2)\sigma_k/\sigma, where \sigma_k is the k-string tension and \sigma that of the fundamental representation. We check this result in a 3D Z_4 gauge model at finite temperature, where a string effect directly related to "c" can be clearly identified.Comment: 7 pages, 5 figures; Talk presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, German