1,519 research outputs found
The Ising model universality of the electroweak theory
Lattice simulations have shown that the first order electroweak phase
transition turns into a regular cross-over at a critical Higgs mass m_{H,c}. We
have developed a method which enables us to make a detailed investigation of
the critical properties of the electroweak theory at m_{H,c}. We find that the
transition falls into the 3d Ising universality class. The continuum limit
extrapolation of the critical Higgs mass is m_{H,c} = 72(2) GeV, which implies
that there is no electroweak phase transition in the Standard Model.Comment: 3 pages, contribution to LATTICE98(electroweak
An all-order discontinuity at the electroweak phase transition
We define a non-local gauge-invariant Green's function which can distinguish
between the symmetric (confinement) and broken (Higgs) phases of the hot
SU(2)xU(1) electroweak theory to all orders in the perturbative expansion. It
is related to the coupling of the Chern-Simons number to a massless Abelian
gauge field. The result implies either that there is a way to distinguish
between the phases, even though the macroscopic thermodynamical properties of
the system have been observed to be smoothly connected, or that the
perturbative Coleman-Hill theorem on which the argument is based, is
circumvented by non-perturbative effects. We point out that this question could
in principle be studied with three-dimensional lattice simulations.Comment: 9 pages; misprint corrected, reference and small clarifications
added; to appear in Phys.Lett.
Critical behaviour of the Ginzburg-Landau model in the type II region
We study the critical behaviour of the three-dimensional U(1) gauge+Higgs
theory (Ginzburg-Landau model) at large scalar self-coupling \lambda (``type II
region'') by measuring various correlation lengths as well as the
Abrikosov-Nielsen-Olesen vortex tension. We identify different scaling regions
as the transition is approached from below, and carry out detailed comparisons
with the criticality of the 3d O(2) symmetric scalar theory.Comment: Lattice2001(higgssusy), 3 page
The non-perturbative QCD Debye mass from a Wilson line operator
According to a proposal by Arnold and Yaffe, the non-perturbative
g^2T-contribution to the Debye mass in the deconfined QCD plasma phase can be
determined from a single Wilson line operator in the three-dimensional pure
SU(3) gauge theory. We extend a previous SU(2) measurement of this quantity to
the physical SU(3) case. We find a numerical coefficient which is more accurate
and smaller than that obtained previously with another method, but still very
large compared with the naive expectation: the correction is larger than the
leading term up to T ~ 10^7 T_c, corresponding to g^2 ~ 0.4. At moderate
temperatures T ~ 2 T_c, a consistent picture emerges where the Debye mass is
m_D ~ 6T, the lightest gauge invariant screening mass in the system is ~ 3T,
and the purely magnetic operators couple dominantly to a scale ~ 6T. Electric
(~ gT) and magnetic (~ g^2T) scales are therefore strongly overlapping close to
the phase transition, and the colour-electric fields play an essential role in
the dynamics.Comment: 10 pages; typos corrected, to appear in Phys.Lett.
Results from 3D Electroweak Phase Transition Simulations
We study the phase transition in SU(2)-Higgs model on the lattice using the
3D dimensionally reduced formalism. The 3D formalism enables us to obtain
highly accurate Monte Carlo results, which we extrapolate both to the infinite
volume and to the continuum limit. Our formalism also provides for a
well-determined and unique way to relate the results to the perturbation
theory. We measure the critical temperature, latent heat and interface tension
for Higgs masses up to 70 GeV.Comment: 4 pages uuencoded postscript, contribution to LATTICE 9
Gauge-invariant strings in the 3d U(1)+Higgs theory
We describe how the strings, which are classical solutions of the continuum
three-dimensional U(1)+Higgs theory, can be studied on the lattice. The effect
of an external magnetic field is also discussed and the first results on the
string free energy are presented. It is shown that the string free energy can
be used as an order parameter when the scalar self-coupling is large and the
transition is continuous.Comment: LATTICE98(higgs); missing author added, no changes to tex
Four-loop logarithms in 3d gauge + Higgs theory
We discuss the logarithmic contributions to the vacuum energy density of the
three-dimensional SU(3) + adjoint Higgs theory in its symmetric phase, and
relate them to numerical Monte Carlo simulations. We also comment on the
implications of these results for perturbative and non-perturbative
determinations of the pressure of finite-temperature QCD.Comment: 3 pages, Lattice2002(nonzerot
The Electroweak Phase Transition in a Magnetic Field
We study the finite temperature electroweak phase transition in an external
hypercharge U(1) magnetic field H_Y, using lattice Monte Carlo simulations. For
sufficiently small fields, H_Y/T^2 < 0.3, the magnetic field makes the first
order transition stronger, but it still turns into a crossover for Higgs masses
m_H ~ 80 GeV. For larger fields, we observe a mixed phase analogous to a type I
superconductor, where a single macroscopic tube of the symmetric phase,
parallel to H_Y, penetrates through the broken phase. For the magnetic fields
and Higgs masses studied, we did not see indications of the expected
Ambjorn-Olesen phase, which should be similar to a type II superconductor.Comment: 20 pages, 7 figures. Discussion on lattice results extended. To
appear in Nucl.Phys.
Measuring infrared contributions to the QCD pressure
For the pressure (or free energy) of QCD, four-dimensional (4d) lattice data
is available at zero baryon density up to a few times the critical temperature
. Perturbation theory, on the other hand, has serious convergence problems
even at very high temperatures. In a combined analytical and three-dimensional
(3d) lattice method, we show that it is possible to compute the QCD pressure
from about to infinity. The numerical accuracy is good enough to
resolve in principle, e.g., logarithmic contributions related to 4-loop
perturbation theory.Comment: 3 pages; talk by Y. Schroder at Lattice2001(hightemp
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