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Register a new userThe Landau gauge gluon propagator at zero and finite temperature: accounting for the combined finite lattice spacing and finite volume effects
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In the past years a good comprehension of the infrared gluon propagator has been achieved, with a good qualitative agreement between lattice results and Dyson-Schwinger equations. However, lattice simulations have been performed at physical volumes which are close to 20 fm but using a large lattice spacing. The interplay between volume effects and lattice spacing effects has not been investigated. Here we aim to fill this gap and address how the two effects change the gluon propagator in the infrared region. Furthermore, we provide infinite volume extrapolations which take into account the finite volume and finite lattice spacing. We also report on preliminary results for the gluon propagator at finite temperature.
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The lattice Landau gauge gluon propagator at finite temperature is computed including the non-zero Matsubara frequencies. Furthermore, the Kallen-Lehmann representation is inverted and the corresponding spectral density evaluated using a Tikhonov regularisation together with the Morozov discrepancy principle. Implications for gluon confinement are discussed.
We study the Landau gauge quark propagator, at finite temperature, using quenched lattice simulations. Special focus is given to the behaviour of the momentum space form factors across the confinement-deconfinement phase transition.
For the gluon propagator of pure SU(2) lattice gauge theory in the Landau gauge we investigate the effect of Gribov copies and finite-volume effects. Concerning gauge fixing, we enlarge the accessible gauge orbits by adding non-periodic Z(2) gauge transformations and systematically employ the simulated annealing algorithm. Strategies to keep all Z(2) sectors under control within reasonable CPU time are discussed. We demonstrate that the finite-volume effects in the infrared regime become ameliorated. Reaching a physical volume of about (6.5 fm)^4, we find that the propagator, calculated with the indicated improvements, becomes flat in the region of smallest momenta. First signs in 4d of a final decrease towards vanishing momentum are discussed.
The quark propagator at finite temperature is investigated using quenched gauge configurations. The propagator form factors are investigated for temperatures above and below the gluon deconfinement temperature $T_c$ and for the various Matsubara frequencies. Significant differences between the functional behaviour below and above $T_c$ are observed both for the quark wave function and the running quark mass. The results for the running quark mass indicate a strong link between gluon dynamics, the mechanism for chiral symmetry breaking and the deconfinement mechanism. For temperatures above $T_c$ and for low momenta, our results support also a description of quarks as free quasi-particles.
We address the interpretation of the Landau gauge gluon propagator at finite temperature as a massive type bosonic propagator. Using pure gauge SU(3) lattice simulations at a fixed lattice volume $sim(6.5fm)^3$, we compute the electric and magnetic form factors, extract a gluon mass from Yukawa-like fits, and study its temperature dependence. This is relevant both for the Debye screening at high temperature $T$ and for confinement at low $T$.
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