Approaching the chiral point in two-flavour lattice simulations

We investigate the behaviour of the pion decay constant and the pion mass in two-flavour lattice QCD, with the physical and chiral points as ultimate goal. Measurements come from the ensembles generated by the CLS initiative using the O(a)-improved Wilson formulation, with lattice spacing down to about 0.05 fermi and pion masses as low as 190 MeV. The applicability of SU(2) chiral perturbation theory is investigated, and various functional forms, and their range of validity, are compared. The physical scale is set through the kaon decay constant, whose measurement is enabled by inserting a third, heavier valence strange quark.Comment: 6 pages, 4 figures. Proceedings for "Excited QCD 2014", Bjelasnica, February 2-8 2014. To appear in Acta Phys. Polon. B Proc. Suppl. Typeset with "appolb.cls

Quarkyonic percolation in dense nuclear matter

We examine the phase diagram of hadronic matter when the number of colours $N_c$, as well as temperature and density, are varied. We show that in this regime a new percolation phase transition is possible, and examine the implications of this transition for extrapolations to physical QCD of the large-N_c limit.Comment: 6 pages; 4 figures; proceeding for Excited QCD 2012 - May 6-12, Peniche, Portuga

Effective Polyakov-loop theory for pure Yang-Mills from strong coupling expansion

Lattice Yang-Mills theories at finite temperature can be mapped onto effective 3d spin systems, thus facilitating their numerical investigation. Using strong-coupling expansions we derive effective actions for Polyakov loops in the $SU(2)$ and $SU(3)$ cases and investigate the effect of higher order corrections. Once a formulation is obtained which allows for Monte Carlo analysis, the nature of the phase transition in both classes of models is investigated numerically, and the results are then used to predict -- with an accuracy within a few percent -- the deconfinement point in the original 4d Yang-Mills pure gauge theories, for a series of values of $N_\tau$ at once.Comment: 14 pages, 7 figures. Proceedings for The XXVIII International Symposium on Lattice Field Theory, Lattice2010, Villasimius, Ital

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