9,082 research outputs found
A non-chiral extension of the standard model with mirror fermions
The difficulties of defining chiral gauge theories non-perturbatively suggest
a vector-like extension of the standard model with three mirror fermion
families. Some phenomenological implications of such an extension are
discussed.Comment: latex, 6 pages, 1 figure with epsfig. Talk given at the workshop
"Beyond the Standard Model V", Balholm, Norway, May 199
Numerical simulation with light Wilson-quarks
The computational cost of numerical simulations of QCD with light dynamical
Wilson-quarks is estimated by determining the autocorrelation of various
quantities. In test runs the expected qualitative behaviour of the pion mass
and coupling at small quark masses is observed.Comment: 5 pages, 3 figures, to appear in the Proceedings of SEWM, Heidelberg,
200
Chiral Fermions on the Lattice
A recently proposed method for regularizing chiral gauge theories
non-perturbatively is discussed in detail. The result is an effective action
which can be computed from the lattice gauge field, and which is suited for
numerical simulations.Comment: Talk given by G. Schierholz at Yukawa International Seminar on
Non-Perturbative QCD: Structure of the QCD Vacuum (YKIS97), Kyoto, December
1997; typos correcte
Confinement in Three Dimensions and the Electroweak Phase Transition
The infrared behaviour of the standard model at finite temperature is
determined by the confining phase of the SU(2)-Higgs model in three dimensions.
Due to the Landau singularity of the three-dimensional gauge theory the
perturbative treatment of the electroweak phase transition breaks down for
Higgs masses above a critical mass . Based on a renormalization group
improved effective potential we find 70 GeV. The scalar
self-coupling has a Landau-type singularity also in the abelian U(1)-Higgs
model, which leads to a breakdown of perturbation theory in the symmetric
phase.Comment: 9 pages, DESY-94-045, 4 figures can be obtained via e-mail from
[email protected]
Numerical simulation tests with light dynamical quarks
Two degenerate flavours of quarks are simulated with small masses down to
about one fifth of the strange quark mass by using the two-step multi-boson
(TSMB) algorithm. The lattice size is 8^3 x 16 with lattice spacing about
0.27fm which is not far from the N_t=4 thermodynamical cross-over line.
Autocorrelations of different physical quantities are estimated as a function
of the quark mass. The eigenvalue spectra of the Wilson-Dirac operator are
investigated.Comment: 14 pages, 7 figures, uses svjour.cls; mistake in the autocorrelation
of the pion mass corrected, version accepted for publication on Eur. Phys. J.
Simulating the Electroweak Phase Transition in the SU(2) Higgs Model
Numerical simulations are performed to study the finite temperature phase
transition in the SU(2) Higgs model on the lattice. In the presently
investigated range of the Higgs boson mass, below 50 GeV, the phase transition
turns out to be of first order and its strength is rapidly decreasing with
increasing Higgs boson mass. In order to control the systematic errors, we also
perform studies of scaling violations and of finite volume effects.Comment: 46 pages with 16 figures, DESY-94-15
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