1,440 research outputs found
Violation of Wiedemann-Franz law at the Kondo breakdown quantum critical point
We study both the electrical and thermal transport near the heavy-fermion
quantum critical point (QCP), identified with the breakdown of the Kondo effect
as an orbital selective Mott transition. We show that the contribution to the
electrical conductivity comes mainly from conduction electrons while the
thermal conductivity is given by both conduction electrons and localized
fermions (spinons), scattered with dynamical exponent . This scattering
mechanism gives rise to a quasi-linear temperature dependence of the electrical
and thermal resistivity. The characteristic feature of the Kondo breakdown
scenario turns out to be emergence of additional entropy carriers, that is,
spinon excitations. As a result, we find that the Wiedemann-Franz ratio should
be larger than the standard value, a fact which enables to differentiate the
Kondo breakdown scenario from the Hertz-Moriya-Millis framework
Numerical Investigation of a Mesoscopic Vehicular Traffic Flow Model Based on a Stochastic Acceleration Process
In this paper a spatial homogeneous vehicular traffic flow model based on a
stochastic master equation of Boltzmann type in the acceleration variable is
solved numerically for a special driver interaction model. The solution is done
by a modified direct simulation Monte Carlo method (DSMC) well known in non
equilibrium gas kinetic. The velocity and acceleration distribution functions
in stochastic equilibrium, mean velocity, traffic density, ACN, velocity
scattering and correlations between some of these variables and their car
density dependences are discussed.Comment: 23 pages, 10 figure
New Formulation of Causal Dissipative Hydrodynamics: Shock wave propagation
The first 3D calculation of shock wave propagation in a homogeneous QGP has
been performed within the new formulation of relativistic dissipative
hydrodynamics which preserves the causality. We found that the relaxation time
plays an important role and also affects the angle of Mach cone.Comment: 4 pages, 1 figure, Proceedings of Quark Matter 200
Resolution of Linear Algebra for the Discrete Logarithm Problem Using GPU and Multi-core Architectures
In cryptanalysis, solving the discrete logarithm problem (DLP) is key to
assessing the security of many public-key cryptosystems. The index-calculus
methods, that attack the DLP in multiplicative subgroups of finite fields,
require solving large sparse systems of linear equations modulo large primes.
This article deals with how we can run this computation on GPU- and
multi-core-based clusters, featuring InfiniBand networking. More specifically,
we present the sparse linear algebra algorithms that are proposed in the
literature, in particular the block Wiedemann algorithm. We discuss the
parallelization of the central matrix--vector product operation from both
algorithmic and practical points of view, and illustrate how our approach has
contributed to the recent record-sized DLP computation in GF().Comment: Euro-Par 2014 Parallel Processing, Aug 2014, Porto, Portugal.
\<http://europar2014.dcc.fc.up.pt/\>
Emission times and opacities from interferometry in non-central Relativistic Nuclear Collisions
The nuclear overlap zone in non-central relativistic heavy ion collisions is
azimuthally very asymmetric. By varying the angle between the axes of
deformation and the transverse direction of the pair momenta, the transverse
HBT radii oscillate in a characteristic way. It is shown that these
oscillations allow determination of source sizes, deformations as well as the
opacity and duration of emission of the source created in any non-central high
energy nuclear collisions. The behavior of the physical quantities with
centrality of the collisions is discussed --- in particular changes caused by a
possible phase transition to a quark-gluon plasma.Comment: Revised version, to appear in Phys. Rev. Letter
Theory of thermal and charge transport in diffusive normal metal / superconductor junctions
Thermal and charge transport in the diffusive normal metal(DN) / insulator /
-, - and p-wave superconductor junctions are studied for various
situations, where we have used the Usadel equation with Nazarov's generalized
boundary condition. Thermal and electrical conductance of the junction and the
Lorentz ratio are calculated by varying the magnitudes of the resistance, the
Thouless energy and the magnetic scattering rate in DN, the transparency of the
insulating barrier, and the angle between the normal to the interface and the
crystal axis of d-wave superconductors or the angle between the normal to the
interface and the lobe direction of the p-wave pair potential. New general
expression is derived for the calculation of the thermal conductance. It is
demonstrated that the proximity effect doesn't influence the thermal
conductance while the mid gap Andreev resonant states suppress it. We have also
discussed a possibility of distinguishing pairing symmetries based on the
dependencies of the electrical and thermal conductance on temperatures.Comment: 21 pages, 20 figures, stylistic changes in v
Energy loss in high energy heavy ion collisions from the Hydro+Jet model
We investigate the effect of energy loss of jets in high energy heavy ion
collisions by using a full three-dimensional space-time evolution of a fluid
combined with (mini-)jets that are explicitly evolved in space-time. In order
to fit the pi^0 data for the Au+Au collisions at sqrt(s_{NN}) = 130 GeV, the
space-time averaged energy loss dE/dx(tau <= 3 fm/c) = 0.36 GeV/fm is extracted
within the model. It is found that most energy loss occurs at the very early
time less than 2 fm/c in the QGP phase and that energy loss in the mixed phase
is negligible within our parameterization for jet energy loss. This is a
consequence of strong expansion of the system.Comment: 4 pages, 5 figures; one figure adde
Dependence of energy loss of jets on the initial thermodynamic state of deconfined matter at RHIC
The dependence of the radiative energy loss of fast partons on the initial
thermodynamic parameters is studied for deconfined matter to be expected at
RHIC. We demonstrate that the specific QCD radiation pattern with a quadratic
dependence of the energy loss on the propagated distance leads to a strong
increase of the energy loss with increasing initial entropy of deconfined
matter supposed its life-time is less than the average time to pass through the
medium. This is in contrast to a parameterization with constant energy loss per
unit length of propagation. For a sufficiently high initial temperature a
two-regime behavior of the energy loss as a function of the initial parton
momentum occurs. The angular structure of the energy loss of hard jets with
respect to the initial temperature is also discussed for RHIC conditions.Comment: 10 pages with fig
Jet Quenching via Jet Collimation
The ATLAS Collaboration recently reported strong modifications of dijet
properties in heavy ion collisions. In this work, we discuss to what extent
these first data constrain already the microscopic mechanism underlying jet
quenching. Simple kinematic arguments lead us to identify a frequency
collimation mechanism via which the medium efficiently trims away the soft
components of the jet parton shower. Through this mechanism, the observed dijet
asymmetry can be accomodated with values of that lie in the
expected order of magnitude.Comment: 6 pages, 4 figure
Azimuthal anisotropy of jet quenching at LHC
We analyze the azimuthal anisotropy of jet spectra due to energy loss of hard
partons in quark-gluon plasma, created initially in nuclear overlap zone in
collisions with non-zero impact parameter. The calculations are performed for
semi-central Pb-Pb collisions at LHC energy.Comment: Talk given at Fourth International Conference "Physics and
Astrophysics of Quark-Gluon Plasma", November 26-30, 2001; 4 pages including
4 eps-figure
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