371 research outputs found
't Hooft-Polyakov monopoles in lattice SU(N)+adjoint Higgs theory
We investigate twisted C-periodic boundary conditions in SU(N) gauge field
theory with an adjoint Higgs field. We show that with a suitable twist for even
N one can impose a non-zero magnetic charge relative to residual U(1) gauge
groups in the broken phase, thereby creating a 't Hooft-Polyakov magnetic
monopole. This makes it possible to use lattice Monte-Carlo simulations to
study the properties of these monopoles in the quantum theory.Comment: 15 pages, 6 figure
Extended Double Lattice BRST, Curci-Ferrari Mass and the Neuberger Problem
We present Extended Double BRST on the lattice and extend the Neuberger
problem to include the ghost/anti-ghost symmetric formulation of the non-linear
covariant Curci-Ferrari (CF) gauges. We then show how a CF mass regulates the
0/0 indeterminate form of physical observables, as observed by Neuberger, and
discuss the gauge-parameter and mass dependence of the model.Comment: Prepared for 7th Conference on Quark Confinement and the Hadron
Spectrum, Ponta Delgada, Azores, Portugal, 2-7 Sep 2006. 3p
Comparing SU(2) to SU(3) gluodynamics on large lattices
We study the SU(2) gluon and ghost propagators in Landau gauge on lattices up
to a size of 112^4. A comparison with the SU(3) case is made and finite-volume
effects are then investigated. We find that for a large range of momenta the
SU(2) and SU(3) propagators are remarkably alike. In the low-momentum region we
compare with recent results obtained in DSE studies on a 4-torus.Comment: 7 pages, 5 figures, poster presented at the XXV International
Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg,
German
On dynamical gluon mass generation
The effective gluon propagator constructed with the pinch technique is
governed by a Schwinger-Dyson equation with special structure and gauge
properties, that can be deduced from the correspondence with the background
field method. Most importantly the non-perturbative gluon self-energy is
transverse order-by-order in the dressed loop expansion, and separately for
gluonic and ghost contributions, a property which allows for a meanigfull
truncation. A linearized version of the truncated Schwinger-Dyson equation is
derived, using a vertex that satisfies the required Ward identity and contains
massless poles. The resulting integral equation, subject to a properly
regularized constraint, is solved numerically, and the main features of the
solutions are briefly discussed.Comment: Special Article - QNP2006: 4th International Conference on Quarks and
Nuclear Physics, Madrid, Spain, 5-10 June 200
Temperature Dependence of Gluon and Ghost Propagators in Landau-Gauge Yang-Mills Theory below the Phase Transition
The Dyson-Schwinger equations of Landau-gauge Yang-Mills theory for the gluon
and ghost propagators are investigated. Numerical results are obtained within a
truncation scheme which has proven to be successful at vanishing temperature.
For temperatures up to 250 MeV we find only minor quantitative changes in the
infrared behaviour of the gluon and ghost propagators. The effective action
calculated from these propagators is temperature-independent within the
numerical uncertainty.Comment: 9 pages, 14 figures, submitted to EPJ C, typos corrected, reference
and 2 minor clarifications added, in v3: one paragraph extended, some
references added, version to appear in EPJ
QCD Propagators at non-vanishing temperatures
We investigate the behaviour of the gluon and ghost propagators, especially
their infrared properties, at non-vanishing temperatures. To this end we solve
their Dyson-Schwinger equations on a torus and find an infrared enhanced ghost
propagator and an infrared vanishing gluon propagator.Comment: 2 pages, 2 figures; talk given by B.G. at the Erice summer school on
Nuclear Physics, Sept. 16 -- 24, 2003, Erice, Ital
Landau gauge ghost and gluon propagators and the Faddeev-Popov operator spectrum
In this talk we report on a recent lattice investigation of the Landau gauge
gluon and ghost propagators in pure SU(3) lattice gauge theory with a special
emphasis on the Gribov copy problem. In the (infrared) region of momenta we find the corresponding MOM scheme running coupling
to rise in . We also report on a first SU(3) computation of
the ghost-gluon vertex function showing that it deviates only weakly from being
constant. In addition we study the spectrum of low-lying eigenvalues and
eigenfunctions of the Faddeev-Popov operator as well as the spectral
representation of the ghost propagator.Comment: talk given by M. M.-P. at the Workshop on Computational Hadron
Physics, Cyprus, September 200
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