155 research outputs found
Numerical tests of the electroweak phase transition and thermodynamics of the electroweak plasma
The finite temperature phase transition in the SU(2) Higgs model at a Higgs
boson mass GeV is studied in numerical simulations on
four-dimensional lattices with time-like extensions up to . The effects
of the finite volume and finite lattice spacing on masses and couplings are
studied in detail. The errors due to uncertainties in the critical hopping
parameter are estimated. The thermodynamics of the electroweak plasma near the
phase transition is investigated by determining the relation between energy
density and pressure.Comment: latex2e, 32 pages, 11 figures with epsfig; A few comments and a new
table are adde
População de plantas de soja no sistema de semeadura direta para o Centro-Sul do Estado do Paraná.
bitstream/item/53984/1/47.pd
Electroweak phase transition by four dimensional simulations
The finite temperature phase transition in the SU(2)-Higgs model at a Higgs
boson mass GeV is studied in numerical simulations on four
dimensional lattices with time-like extensions up to . is
extrapolated to the continuum limit and a comparison with the perturbative
prediction is made. A one-loop calculation to the coupling anisotropies of the
SU(2)-Higgs model on lattices with asymmetric lattice spacings is presented.
Our numerical simulations show that the above perturbative result is applicable
in the phenomenologically interesting parameter region.Comment: 3 pages, Latex, 3 figures, Talk presented at LATTICE96(electroweak)
by Z. Fodo
Rendimento de graos em diferentes sistemas de preparo e manejo de solos.
Material e metodos: amostragem e avaliacao; Resultados e discussao: primeira etapa de 1978 ate 1986 - 17 cultivos; Segunda etapa: de 1987 ate 1990 - cultivos 18 a 23; Conclusoes e recomendacoes; Implicacoes praticas dos resultados experimentais.bitstream/item/60909/1/Documentos-61.pd
Identification of the critical temperature from non-equilibrium time-dependent quantities
We present a new procedure able to identify and measure the critical
temperature. This method is based on the divergence of the relaxation time
approaching the critical point in quenches from infinite temperature. We
introduce a dimensionless quantity that turns out to be time-independent at the
critical temperature. The procedure does not need equilibration and allows for
a relatively fast identification of the critical temperature. The method is
first tested in the ferromagnetic Ising model and then applied to the
one-dimensional Ising spin glass with power-law interactions. Here we always
find a finite critical temperature also in presence of a uniform external
field, in agreement with the mean-field picture for the low temperature phase
of spin glasses.Comment: 6 pages, 10 figure
Numerical Simulations and the Strength of the Electroweak Phase Transition
Numerical simulations are performed to study the finite temperature phase
transition in the SU(2) Higgs model on the lattice. The strength of the first
order phase transition is investigated by determining the latent heat and the
interface tension on lattices. The values of the Higgs boson mass
presently chosen are below 50 GeV. Our results are in qualitative agreement
with two-loop resummed perturbation theory.Comment: (Only a few minor changes compared to the original version.) 9 pages
and 2 figures, DESY-94-08
Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY
The ARES linac at DESY aims to generate and characterize ultrashort electron
bunches (fs to sub-fs duration) with high momentum and arrival time stability
for the purpose of applications related to accelerator R&D, e.g. development of
advanced and compact diagnostics and accelerating structures, test of new
accelerator components, medical applications studies, machine learning, etc.
During its commissioning phase, the bunch duration characterization of the
electron bunches generated at ARES has been performed with an RF-phasing
technique relying on momentum spectra measurements, using only common
accelerator elements (RF accelerating structures and magnetic spectrometers).
The sensitivity of the method allowed highlighting different response times for
Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of
machine parameters shows excellent agreement overall with the simulation
predictions, thus demonstrating a very good understanding of the ARES operation
on the bunch duration aspect. The importance of a precise in-situ experimental
determination of the phase velocity of the first travelling wave accelerating
structure after the electron source, for which we propose a simple new
beam-based method precise down to sub-permille variation respective to the
speed of light in vacuum, is emphasized for this purpose. A minimum bunch
duration of 20 fs rms, resolution-limited by the space charge forces, is
reported. This is, to the best of our knowledge, around 4 times shorter than
what has been previously experimentally demonstrated based on RF-phasing
techniques with a single RF structure. The present study constitutes a strong
basis for future time characterization down to the sub-fs level at ARES, using
dedicated X-band transverse deflecting structures.Comment: 17 pages, 11 figures. To be submitted to Physical Review Accelerators
and Beam
Monte Carlo Simulations of Short-time Critical Dynamics with a Conserved Quantity
With Monte Carlo simulations, we investigate short-time critical dynamics of
the three-dimensional anti-ferromagnetic Ising model with a globally conserved
magnetization (not the order parameter). From the power law behavior of
the staggered magnetization (the order parameter), its second moment and the
auto-correlation, we determine all static and dynamic critical exponents as
well as the critical temperature. The universality class of is the same
as that without a conserved quantity, but the universality class of non-zero
is different.Comment: to appear in Phys. Rev.
Corrections to Scaling for the Two-dimensional Dynamic XY Model
With large-scale Monte Carlo simulations, we confirm that for the
two-dimensional XY model, there is a logarithmic correction to scaling in the
dynamic relaxation starting from a completely disordered state, while only an
inverse power law correction in the case of starting from an ordered state. The
dynamic exponent is .Comment: to appear as a Rapid commu. in Phys. Rev.
Hexatic Order and Surface Ripples in Spherical Geometries
In flat geometries, two dimensional hexatic order has only a minor effect on
capillary waves on a liquid substrate and on undulation modes in lipid
bilayers. However, extended bond orientational order alters the long wavelength
spectrum of these ripples in spherical geometries. We calculate this frequency
shift and suggest that it might be detectable in lipid bilayer vesicles, at the
surface of liquid metals and in multielectron bubbles in liquid helium at low
temperatures. Hexatic order also leads to a shift in the threshold for the
fission instability induced in the later two systems by an excess of electric
charge.Comment: 5 pages, 1 figure; revised version; to appear in Phys. Rev. Let
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