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On planar quantum dynamics of a magnetic dipole moment in the presence of electric and magnetic fields
The planar quantum dynamics of a neutral particle with a magnetic dipole
moment in the presence of electric and magnetic fields is considered. The
criteria to establish the planar dynamics reveal that the resulting
nonrelativistic Hamiltonian has a simplified expression without making
approximations, and some terms have crucial importance for system dynamics
Gribov copies, Lattice QCD and the gluon propagator
We address the problem of Gribov copies in lattice QCD. The gluon propagator
is computed, in the Landau gauge, using 302 ()
configurations gauge fixed to different copies. The results of the simulation
shows that: i) the effect of Gribov copies is small (less than 10%); ii) Gribov
copies change essentially the lowest momenta components ( GeV); iii)
within the statistical accuracy of our simulation, the effect of Gribov copies
is resolved if statistical errors are multiplied by a factor of two or three.
Moreover, when modelling the gluon propagator, different sets of Gribov copies
produce different sets of parameters not, necessarily, compatible within one
standard deviation. Finally, our data supports a gluon propagator which, for
large momenta, behaves like a massive gluon propagator with a mass of 1.1 GeV
The Infrared Landau Gauge Gluon Propagator from Lattice QCD
The quenched Landau gauge gluon propagator is investigated in lattice QCD
with large assimetric lattices, accessing momenta as low as 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
and are measured.Comment: 3 pages, 1 figure. Talk given at Quark Confinement and the Hadron
Spectrum VI 2004, Italy, 21-25 Sep. References correc
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