1,980 research outputs found
Investigations on the deconfining phase transition in QCD
We investigate the deconfining phase transition in SU(3) pure gauge theory
and in full QCD with two flavors of staggered fermions by means of a gauge
invariant thermal partition functional. In the pure gauge case our finite size
scaling analysis is in agreement with the well known weak first order phase
transition. In the case of 2 flavors full QCD we find that the phase transition
is consistent with weak first order, contrary to the expectation of a crossover
for not too large quark masses.Comment: 3 pages, 3 figures, Lattice2003(topology
Long-wavelength excitations of Higgs condensates
Quite independently of the Goldstone phenomenon, recent lattice data suggest
the existence of gap-less modes in the spontaneously broken phase of a theory. This result is a direct consequence of the quantum nature of
the `Higgs condensate' that cannot be treated as a purely classical c-number
field.Comment: 6 page
Indications on the Higgs boson mass from lattice simulations
The `triviality' of has been traditionally interpreted within
perturbation theory where the prediction for the Higgs boson mass depends on
the magnitude of the ultraviolet cutoff . This approach crucially
assumes that the vacuum field and its quantum fluctuations rescale in the same
way. The results of the present lattice simulation, confirming previous
numerical indications, show that this assumption is not true. As a consequence,
large values of the Higgs mass can coexist with the limit . As an example, by extrapolating to the Standard Model our results
obtained in the Ising limit of the one-component theory, one can obtain a value
as large as GeV, independently of .Comment: 3 pages, 2 figures, Lattice2003(higgs
Color Dynamics in External Fields
We investigate the vacuum dynamics of U(1), SU(2), and SU(3) lattice gauge
theories in presence of external (chromo)magnetic fields, both in (3+1) and
(2+1) dimensions. We find that the critical coupling for the phase transition
in compact U(1) gauge theory is independent of the strength of an external
magnetic field. On the other hand we find that, both in (3+1) and (2+1)
dimensions, the deconfinement temperature for SU(2) and SU(3) gauge systems in
a constant abelian chromomagnetic field decreases when the strength of the
applied field increases. We conclude that the dependence of the deconfinement
temperature on the strength of an external constant chromomagnetic field is a
peculiar feature of non abelian gauge theories and could be useful to get
insight into color confinement.Comment: 26 pages, 14 figure
The phase diagram of QCD with four degenerate quarks
We revisit the determination of the pseudo-critical line of QCD with four
degenerate quarks at non-zero temperature and baryon density by the method of
analytic continuation. We determine the pseudo-critical couplings at imaginary
chemical potentials by high-statistics Monte Carlo simulations and reveal
deviations from the simple quadratic dependence on the chemical potential
visible in earlier works on the same subject. Finally, we discuss the
implications of our findings for the shape of the pseudo-critical line at real
chemical potential, comparing different possible extrapolations.Comment: 8 pages, 8 figures, 2 table
Monopole Condensation in full QCD using the Schroedinger Functional
We use a lattice thermal partition functional to study Abelian monopole
condensation in full QCD with staggered fermions. We present
preliminary results on and lattices.Comment: Lattice2002(topology). 3 pages, 3 figure
Probing the non-perturbative dynamics of SU(2) vacuum
The vacuum dynamics of SU(2) lattice gauge theory is studied by means of a
gauge-invariant effective action defined using the lattice Schr\"odinger
functional. Numerical simulations are performed both at zero and finite
temperature. The vacuum is probed using an external constant Abelian
chromomagnetic field. The results suggest that at zero temperature the external
field is screened in the continuum limit. On the other hand at finite
temperature it seems that confinement is restored by increasing the strength of
the applied field.Comment: 29 pages, 10 figures, LaTeX2
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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