211 research outputs found
Diquark condensation in dense SU(2) matter
We report on a lattice study of two-color QCD with adjoint staggered fermions
at high density. We find that the model has no early onset and we report on
results for diquark condensation, from simulations with and without a diquark
source term.Comment: Lattice2001(hightemp
Lattice QCD with light dynamical quarks
We report on the simulation of QCD with light dynamical quarks using the
two-step multi-boson (TSMB) algorithm.
In an exploratory study with two flavours of quarks at lattice spacing about
0.27 fm and with quark mass down to one sixth of the strange quark mass
eigenvalue spectra and autocorrelations have been studied.
Here we present results on the volume dependence as well as tests of possible
algorithmic improvements.Comment: 6 pages, Lattice2002(spectrum
Mass Spectrum and Bounds on the Couplings in Yukawa Models With Mirror-Fermions
The symmetric Yukawa model with mirror-fermions
in the limit where the mirror-fermion is decoupled is studied both analytically
and numerically. The bare scalar self-coupling is fixed at zero and
infinity. The phase structure is explored and the relevant phase transition is
found to be consistent with a second order one. The fermionic mass spectrum
close to that transition is discussed and a first non-perturbative estimate of
the influence of fermions on the upper and lower bounds on the renormalized
scalar self-coupling is given. Numerical results are confronted with
perturbative predictions.Comment: 7 (Latex) page
Partially quenched chiral perturbation theory and numerical simulations
The dependence of the pseudoscalar meson mass and decay constant is compared
to one-loop Partially Quenched Chiral Perturbation Theory (PQChPT) in a
numerical simulation with two light dynamical quarks. The characteristic
behaviour with chiral logarithms is observed. The values of the fitted
PQChPT-parameters are in a range close to the expectation in continuum in spite
of the fact that the lattice spacing is still large, namely a=0.28 fm.Comment: 11 pages, 3 figures; discussion of the results in section 3 extende
Quark mass dependence of masses and decay constants of the pseudo-Goldstone bosons in QCD
The dependence of the pseudoscalar meson masses and decay constants on sea
and valence quark masses is compared to next-to-leading order (NLO) Chiral
Perturbation Theory (ChPT). The numerical simulations with two light dynamical
quark flavors are performed with the Wilson-quark lattice action at gauge
coupling beta=5.1 and hopping parameters kappa=0.176, 0.1765, 0.177 on a 16^4
lattice. O(a) lattice artifacts are taken into account by applying chiral
perturbation theory for the Wilson lattice action. The values of the relevant
combinations of Gasser-Leutwyler constants L_4, L_5, L_6 and L_8 are estimated.Comment: 21 pages, 4 figures; discussion of the sea quark mass dependence
changed, references adde
Numerical simulation of heavy fermions in an SU(2)_L x SU(2)_R symmetric Yukawa model
An exploratory numerical study of the influence of heavy fermion doublets on
the mass of the Higgs boson is performed in the decoupling limit of a chiral
symmetric Yukawa model with mirror fermions. The
behaviour of fermion and boson masses is investigated at infinite bare quartic
coupling on , and lattices. A first
estimate of the upper bound on the renormalized quartic coupling as a function
of the renormalized Yukawa-coupling is given.Comment: 15 pp + 11 Figures appended as Postscript file
Large rescaling of the Higgs condensate: theoretical motivations and lattice results
In the Standard Model the Fermi constant is associated with the vacuum
expectation value of the Higgs field, `the condensate', usually believed to be
a cutoff-independent quantity. General arguments related to the `triviality' of
theory in 4 space-time dimensions suggest, however, a dramatic
renormalization effect in the continuum limit that is clearly visible on the
relatively large lattices available today. The result can be crucial for the
Higgs phenomenology and in any context where spontaneous symmetry breaking is
induced through scalar fields.Comment: LATTICE99(Higgs) 3 pages, 3 figure
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