arXiv subjects
Publications and source records attributed to A. Tarancon.
We present numerical results obtained in full QCD with 2 flavors of Wilson fermions. We discuss the relation between the phase of Polyakov loops and the {\bf sea} quarks boundary conditions. We report preliminary results about the HMC autocorrelation of the hadronic masses, on a $16^3 \times 32$ lattice volume, at $β=5.55$ with $k_{sea}=0.1570$.
We propose a family of renormalization group transformations characterized by free parameters that may be tuned in order to reduce the truncation effects. As a check we test them in the three dimensional XY model. The Schwinger--Dyson equations are used to study the renormalization group flow.
We propose a new Real Space Renormalization Group transformation useful for Monte Carlo calculations in theories with global or local symmetries. From relaxation arguments we define the block-spin transformation with two tunable free parameters, adapted to the system's action. Varying them it is possible to place the fixed point very close to the simulation point. We show how the method works in a simple model with global symmetry: the three dimensional XY model.
We have numerically studied the trapping problem in a two-dimensional lattice where particles are continuously generated. We have introduced interaction between particles and directionality of their movement. This model presents a critical behaviour with a rich phase structure similar to spin systems. We interpret a change in the asymptotic density of particles as a phase transition. For high directionality the change is abrupt, possibly of first order. For small directionality the phase transition is of higher order. We have computed the phase diagram, the volume dependence of the critical point, and the relaxation time of the system in the large volume limit.
We compute, on the $(λΦ^4)_{1+1}$ model on the lattice, the soliton mass by means of two very different numerical methods. First, we make use of a ``creation operator'' formalism, measuring the decay of a certain correlation function. On the other hand we measure the shift of the vacuum energy between the symmetric and the antiperiodic systems. The obtained results are fully compatible. We compute the continuum limit of the mass from the perturbative Renormalization Group equations. Special attention is paid to ensure that we are working on the scaling region, where physical quantities remain unchanged along any Renormalization Group Trajectory. We compare the continuum value of the soliton mass with its perturbative value up to one loop calculation. Both quantities show a quite satisfactory agreement. The first is slightly bigger than the perturbative one; this may be due to the contributions of higher order corrections.
The Coulomb-Higgs phase transition of the four dimensional Z$_8$ gauge model is studied. We find clear first order properties in contradiction with the previously stressed second order behavior. That transition point may be regarded as the end of a transition line of the U(1)-Higgs model with charge $q=8$, that has been also assumed of second order. We show that this line is first order in a wide region, with a decreasing latent heat that goes to zero when closing to the 4--$d$ XY model limit.