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We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated. [ABSTRACT FROM AUTHOR]

The infrared behaviour of the lattice Landau gauge gluon propagator is discussed, combining results from simulations with different volumes and lattice spacings. In particular, the Cucchieri-Mendes bounds are computed and their implications for D(0) discussed. [ABSTRACT FROM AUTHOR]

We report on the infrared limit of the quenched lattice Landau gauge gluon propagator computed from large asymmetric lattices. In particular, the compatibility of the pure power law infrared solution (q2)2κ of the Dyson-Schwinger equations is investigated and the exponent κ is measured. Some results for the ghost propagator and for the running coupling constant will also be shown. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The charmonium and bottomonium spectra computed from a potential defined from a single gauge configuration, obtained from solving the classical field equations, is discussed. The theoretical spectra shows good agreement with the measured states. A discussion of possible interpretations, within the same non-relativistic potential model, for the new charmonia states X(3872), χc1(2P) and Y(4260) is performed. In particular, we give predictions for electromagnetic E1 transitions for various scenarios. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The quenched Landau gauge gluon propagator is investigated in lattice QCD with large assimetric lattices, accessing momenta as low as q ∼ 100 MeV or smaller. Our investigation focus on the IR limit of the gluon dressing function, testing the compatibility with recent solutions of the Dyson-Schwinger equations. In particular, the low energy parameters κ and α(0) are measured. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

It is showed that potentials derived from classical solutions of the SU(3) Yang-Mills theory can provide confining potentials that reproduce the heavy quarkonium spectrum within the same level of precision as the Cornell potential. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The connection between QCD, a nonlocal Nambu-Jona-Lasinio type model and the Landau gauge gluon propagator is explored. This two point function is parameterized by a functional form which is compatible with Dyson-Schwinger and lattice QCD results. Demanding the nonlocal model to reproduce the experimental values for the pion mass, the pion decay constant, Γπ→γγ and the light quark condensate we conclude that low energy physics does not distinguish between the so-called decoupling and scaling solutions of the Dyson-Schwinger equations. This result means that, provided that the model parameters are chosen appropriately, one is free to choose any of the above scenarios. Furthermore, the nonlocal Nambu-Jona-Lasinio quark model considered here is chiral invariant and satisfies the GMOR relation at the 1% level of precision. [ABSTRACT FROM AUTHOR]

The solution of Alkofer et al for the gluon propagator in Landau gauge of the Dyson-Schwinger equations was fitted with several functional forms. We study if the lattice gluon propagator, computed using large asymmetric lattices, is well reproduced by such functional forms. Furthermore, we also check for the violation of positivity of the lattice gluon propagator. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]