117 research outputs found
Non-perturbative mass spectrum of an extra-dimensional orbifold
We analyse non-perturbatively a five-dimensional SU(2) gauge theory
compactified on the S^1/Z_2 orbifold. In particular, we present simulation
results for the mass spectrum of the theory, which contains a Higgs and a
photon. The Higgs mass is found to be free of divergences without fine-tuning.
The photon mass is non-zero, thus providing us with the first lattice evidence
for a Higgs mechanism derived from an extra dimension. Data from the static
potential are consistent with dimensional reduction at low energies.Comment: 4 pages, 3 figure
Locality with staggered fermions
We address the locality problem arising in simulations, which take the square
root of the staggered fermion determinant as a Boltzmann weight to reduce the
number of dynamical quark tastes. A definition of such a theory necessitates an
underlying local fermion operator with the same determinant and the
corresponding Green's functions to establish causality and unitarity. We
illustrate this point by studying analytically and numerically the square root
of the staggered fermion operator. Although it has the correct weight, this
operator is non-local in the continuum limit. Our work serves as a warning that
fundamental properties of field theories might be violated when employing
blindly the square root trick. The question, whether a local operator
reproducing the square root of the staggered fermion determinant exists, is
left open.Comment: 24 pages, 7 figures, few remarks added for clarity, accepted for
publication in Nucl. Phys.
String breaking and lines of constant physics in the SU(2) Higgs model
We present results for the ground state and first excited state static
potentials in the confinement "phase" of the SU(2) Higgs model. String breaking
and the crossing of the energy levels are clearly visible. We address the
question of the cut-off effects in our results and observe a remarkable scaling
of the static potentials.Comment: LATTICE99(Higgs), 3 pages, 4 figure
Static potential in the SU(2) Higgs model
We present results for the static potential in the confinement phase of the
SU(2) Higgs model on the lattice. Introducing a suitable matrix correlation
function we observe string breaking at a distance r_b ~ 1.8 r_0, where the
length scale r_0 has a value r_0 ~ 0.5 fm in QCD. The method presented here may
lead the way towards a treatment of string breaking in QCD.Comment: LATTICE98(confine), 3 pages, 3 figure
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