120 research outputs found
Correlation Dynamics of Yukawa-theory in 1+1 dimensions
Using the method of correlation dynamics we investigate the properties of a
field-theory for fermions and scalar bosons coupled via a Yukawa interaction.
Within this approach, which consists in an expansion of full equal-time Green
functions into connected equal-time Green functions and a corresponding
truncation of the hierarchy of equations of motion we carry out calculations up
to 4th order in the connected Green functions and evaluate the effective
potential of the theory in 1+1 dimensions on a torus. Comparing the different
approximations we find a strong influence of the connected 4-point functions on
the properties of the system.Comment: LaTeX, 38 pages, 12 figure
A importância do período seco no sistema de produção de leite.
bitstream/item/32007/1/CT-40online.pd
Diagnóstico preliminar da bacia leiteira de Pinheiro Machado.
bitstream/item/32000/1/DT-109online.pd
Vantagens e desvantagens do elevado valor nutritivo de cereais de inverno na produção de ruminantes.
Shear Viscosity in the O(N) Model
We compute the shear viscosity in the O(N) model at first nontrivial order in
the large N expansion. The calculation is organized using the 1/N expansion of
the 2PI effective action (2PI-1/N expansion) to next-to-leading order, which
leads to an integral equation summing ladder and bubble diagrams. We also
consider the weakly coupled theory for arbitrary N, using the three-loop
expansion of the 2PI effective action. In the limit of weak coupling and
vanishing mass, we find an approximate analytical solution of the integral
equation. For general coupling and mass, the integral equation is solved
numerically using a variational approach. The shear viscosity turns out to be
close to the result obtained in the weak-coupling analysis.Comment: 37 pages, few typos corrected; to appear in JHE
Equilibration within a semiclassical off-shell transport approach
Equilibration times for nuclear matter configurations -- modelling
intermediate and high energy nucleus-nucleus collisions -- are evaluated within
the semiclassical off-shell transport approach developed recently. The
transport equations are solved for a finite box in coordinate space employing
periodic boundary conditions. The off-shell transport model is shown to give
proper off-shell equilibrium distributions in the limit for the
nucleon and -resonance spectral functions. We find that equilibration
times within the off-shell approach are only slightly enhanced as compared to
the on-shell limit for the momentum configurations considered.Comment: 19 pages, LaTeX, including 4 postscript figures, submitted to Nucl.
Phys.
Suplementação proteica e energética para vacas em lactação sob pastejo.
bitstream/item/88340/1/CT442012.pd
The QGP phase in relativistic heavy-ion collisions
The dynamics of partons, hadrons and strings in relativistic nucleus-nucleus
collisions is analyzed within the novel Parton-Hadron-String Dynamics (PHSD)
transport approach, which is based on a dynamical quasiparticle model for
partons (DQPM) matched to reproduce recent lattice-QCD results - including the
partonic equation of state - in thermodynamic equilibrium. The transition from
partonic to hadronic degrees of freedom is described by covariant transition
rates for the fusion of quark-antiquark pairs or three quarks (antiquarks),
respectively, obeying flavor current-conservation, color neutrality as well as
energy-momentum conservation. The PHSD approach is applied to nucleus-nucleus
collisions from low SIS to RHIC energies. The traces of partonic interactions
are found in particular in the elliptic flow of hadrons as well as in their
transverse mass spectra.Comment: To be published by Springer in Proceedings of the International
Symposium on `Exciting Physics', Makutsi-Range, South Africa, 13-20 November,
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