4,919 research outputs found
Inhomogeneous quadratic congruences
We investigate the density of integer solutions to certain binary
inhomogeneous quadratic congruences and use this information to detect almost
primes on a singular del Pezzo surface of degree 6.Comment: 24 page
Deciphering the properties of the medium produced in heavy ion collisions at RHIC by a pQCD analysis of quenched large spectra
We discuss the question of the relevance of perturbative QCD calculations for
analyzing the properties of the dense medium produced in heavy ion collisions.
Up to now leading order perturbative estimates have been worked out and
confronted with data for quenched large hadron spectra. Some of
them are giving paradoxical results, contradicting the perturbative framework
and leading to speculations such as the formation of a strongly interacting
quark-gluon plasma. Trying to bypass some drawbacks of these leading order
analysis and without performing detailed numerical investigations, we collect
evidence in favour of a consistent description of quenching and of the
characteristics of the produced medium within the pQCD framework.Comment: 10 pages, 3 figure
Prompt Photon and Inclusive Production at RHIC and LHC
We present results for prompt photon and inclusive production in p-p
and A-A collisions at RHIC and LHC energies. We include the full
next-to-leading order radiative corrections and nuclear effects, such as
nuclear shadowing and parton energy loss. We find the next-to-leading order
corrections to be large and dependent. We show how measurements of
production at RHIC and LHC, at large , can provide valuable
information about the nature of parton energy loss.
We calculate the ratio of prompt photons to neutral pions and show that at
RHIC energies this ratio increases with approaching one at
GeV, due to the large suppression of production. We show that at the
LHC, this ratio has steep dependence and approaches 10% effect at GeV.Comment: Talk presented by I. Sarcevic, to appear in the Proceedings of Quark
Matter 2002; 4 pages including 4 color figure
Mixed and discontinuous finite volume element schemes for the optimal control of immiscible flow in porous media
We introduce a family of hybrid discretisations for the numerical
approximation of optimal control problems governed by the equations of
immiscible displacement in porous media. The proposed schemes are based on
mixed and discontinuous finite volume element methods in combination with the
optimise-then-discretise approach for the approximation of the optimal control
problem, leading to nonsymmetric algebraic systems, and employing minimum
regularity requirements. Estimates for the error (between a local reference
solution of the infinite dimensional optimal control problem and its hybrid
approximation) measured in suitable norms are derived, showing optimal orders
of convergence
Coulomb effects in the spin-dependent contribution to the intra-beam scattering rate
Coulomb effects in the intra-beam scattering are taken into account in a way
providing correct description of the spin-dependent contribution to the beam
loss rate. It allows one to calculate this rate for polarized beams
at arbitrarily small values of the ratio ,
characterizing relative change of the electron energy in the laboratory system
during scattering event.Comment: 8 pages, 2 figure
Angular Dependence of the Radiative Gluon Spectrum and the Energy Loss of Hard Jets in QCD Media
The induced momentum spectrum of soft gluons radiated from a high energy
quark propagating through a QCD medium is derived in the BDMPS formalism. A
calorimetric measurement for the medium dependent energy lost by a jet with
opening angle is proposed.The fraction of this energy
loss with respect to the integrated one appears to be the relevant
observable.It exhibits a universal behaviour in terms of the variable
where is the size of the medium and
the transport coefficient. Phenomenological implications for the
differences between cold and hot QCD matter are discussed.Comment: 13 pages and 7 figures, RevTe
Anomalous Transport Processes in Anisotropically Expanding Quark-Gluon Plasmas
We derive an expression for the anomalous viscosity in an anisotropically
expanding quark-gluon-plasma, which arises from interactions of thermal partons
with dynamically generated color fields. The anomalous viscosity dominates over
the collisional viscosity for large velocity gradients or weak coupling. This
effect may provide an explanation for the apparent ``nearly perfect'' liquidity
of the matter produced in nuclear collisions at RHIC without the assumption
that it is a strongly coupled state.Comment: 31 pages, 1 figure, some typos in published version are correcte
On p_T-broadening of high energy partons associated with the LPM effect in a finite-volume QCD medium
We study the contributions from radiation to -broadening of a high
energy parton traversing a QCD medium with a finite length . The interaction
between the parton and the medium is described by decorrelated static multiple
scattering. Amplitudes of medium-induced gluon emission and parton self-energy
diagrams are evaluated in the soft gluon limit in the BDMPS formalism. We find
both the double-logarithmic correction from incoherent scattering, which is
parametrically the same as that in single scattering, and the logarithmic
correction from the LPM effect. Therefore, we expect a parametrically large
correction from radiation to the medium-induced -broadening in
perturbative QCD.Comment: 19 pages, focusing only on calculations about the medium-induced
diagrams, origin for double-log reinterpreted, final version to appear in
JHE
O fim do subsídio do trigo e a utilização de farinhas mistas.
bitstream/item/119471/1/FOL-04309.pdfTrabalho apresentado na I Jornada Estadual de Tecnologia de Alimentos e Nutrição Humana, Passo Fundo, 1988
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