Abstract:
we discuss recent results for the phase transition in finite-temperature qcd from numerical (monte carlo) simulations of the lattice-regularized theory. emphasis is given to the case of two degenerate light-quark flavors. the order of the transition in this case, which could have cosmological implications, has not yet been established.

Abstract:
The order of the phase transition in finite-temperature QCD with two degenerate light quarks is still an open problem and corresponds to the last question mark in the zero-density phase diagram of QCD. We argue that establishing the nature of the transition in this case is also a crucial test for numerical simulations of lattice QCD, allowing precise estimates of possible systematic errors related e.g. to the choice of fermion-simulation algorithm or of discretized formulation for fermions.

Abstract:
Monte Carlo simulations applied to the lattice formulation of quantum chromodynamics (QCD) enable a study of the theory from first principles, in a nonperturbative way. After over two decades of developments in the methodology for this study and with present-day computers in the teraflops range, lattice-QCD simulations are now able to provide quantitative predictions with errors of a few percent. This means that these simulations will soon become the main source of theoretical results for comparison with experiments in physics of the strong interactions. It is therefore an important moment for the beginning of Brazilian participation in the field.

Abstract:
We report the results of our quenched lattice simulations of the Wilson action with a nonperturbatively determined clover term at beta=6.2 and compare them with those of the standard Wilson action at the same beta value.

Abstract:
We discuss recent results for the phase transition in finite-temperature QCD from numerical (Monte Carlo) simulations of the lattice-regularized theory. Emphasis is given to the case of two degenerate light-quark flavors. The order of the transition in this case, which could have cosmological implications, has not yet been established.

Abstract:
The chiral transition for two-flavor QCD is predicted to be in the same universality class as the 3d O(4) model. This prediction is verified in the Wilson case, but not for the staggered-fermion case. The comparison is usually done assuming infinite-volume behavior. Here we make an analysis of existing staggered-fermion data using finite-size scaling and normalizing the QCD data. We find better agreement for larger quark masses.

Abstract:
High-precision calculations of hadron spectroscopy are a crucial task for Lattice QCD. State-of-the-art techniques are needed to disentangle the contributions from different energy states, such as solving the generalized eigenvalue problem (GEVP) for zero-momentum hadron correlators in an efficient way. We review the method and discuss its application in the determination of the $B_s$-meson spectrum using (quenched) nonperturbative HQET at order $1/m_b$.

Abstract:
we present a review of our numerical studies of the running coupling constant, gluon and ghost propagators, ghost-gluon vertex and ghost condensate for the case of pure su(2) lattice gauge theory in the minimal landau gauge. emphasis is given to the infrared regime, in order to investigate the confinement mechanisms of qcd. we compare our results to other theoretical and phenomenological studies.

Abstract:
three-dimensional n-vector spin models may define universality classes for such diverse phenomena as i) the superfluid transition in liquid helium (currently investigated in the micro-gravity environment of the space shuttle) and ii) the transition from hadronic matter to a quark-gluon plasma, studied in heavy-ion collisions at the laboratories of brookhaven and cern. the models have been extensively studied both by field-theoretical and by statistical mechanical methods, including monte carlo simulations using cluster algorithms. these algorithms are applicable also in the presence of a magnetic field. key quantities for the description of the transitions above - such as universal critical amplitude ratios and the location of the so-called pseudo-critical line - can be obtained from the models' magnetic equation of state, which relates magnetization, external magnetic field and temperature. here we present an improved parametrization for the equation of state of the models, allowing a better fit to the numerical data. our proposed form is inspired by perturbation theory, with coefficients determined nonperturbatively from fits to the data.

Abstract:
The infrared behavior of gluon and ghost propagators offers a crucial test of confinement scenarios in Yang-Mills theories. A nonperturbative study of these propagators from first principles is possible in lattice simulations, but one must consider significantly large lattice sizes in order to approach the infrared limit. We propose constraints based on general properties of the propagators to gain control over the extrapolation of data to the infinite-volume limit. These bounds also provide a way to relate the propagators to simpler, more intuitive quantities. We apply our analysis to the case of pure SU(2) gauge theory in Landau gauge, using the largest lattice sizes to date. Our results seem to contradict commonly accepted confinement scenarios. We argue that it is not so.