35,020 research outputs found
Unified Gas-kinetic Wave-Particle Methods III: Multiscale Photon Transport
In this paper, we extend the unified gas-kinetic wave-particle (UGKWP) method
to the multiscale photon transport. In this method, the photon free streaming
and scattering processes are treated in an un-splitting way. The duality
descriptions, namely the simulation particle and distribution function, are
utilized to describe the photon. By accurately recovering the governing
equations of the unified gas-kinetic scheme (UGKS), the UGKWP preserves the
multiscale dynamics of photon transport from optically thin to optically thick
regime. In the optically thin regime, the UGKWP becomes a Monte Carlo type
particle tracking method, while in the optically thick regime, the UGKWP
becomes a diffusion equation solver. The local photon dynamics of the UGKWP, as
well as the proportion of wave-described and particle-described photons are
automatically adapted according to the numerical resolution and transport
regime. Compared to the -type UGKS, the UGKWP requires less memory cost
and does not suffer ray effect. Compared to the implicit Monte Carlo (IMC)
method, the statistical noise of UGKWP is greatly reduced and computational
efficiency is significantly improved in the optically thick regime. Several
numerical examples covering all transport regimes from the optically thin to
optically thick are computed to validate the accuracy and efficiency of the
UGKWP method. In comparison to the -type UGKS and IMC method, the UGKWP
method may have several-order-of-magnitude reduction in computational cost and
memory requirement in solving some multsicale transport problems.Comment: 27 pages, 15 figures. arXiv admin note: text overlap with
arXiv:1810.0598
Azimuthal jet flavor tomography with CUJET2.0 of nuclear collisions at RHIC and LHC
A perturbative QCD based jet tomographic Monte Carlo model, CUJET2.0, is
presented to predict jet quenching observables in relativistic heavy ion
collisions at RHIC/BNL and LHC/CERN energies. This model generalizes the DGLV
theory of flavor dependent radiative energy loss by including multi-scale
running strong coupling effects. It generalizes CUJET1.0 by computing jet path
integrations though more realistic 2+1D transverse and longitudinally expanding
viscous hydrodynamical fields contrained by fits to low flow data. The
CUJET2.0 output depends on three control parameters, ,
corresponding to an assumed upper bound on the vacuum running coupling in the
infrared and two chromo-electric and magnetic QGP screening mass scales where is the 1-loop Debye mass. We compare
numerical results as a function of for pure and deformed HTL
dynamically enhanced scattering cases corresponding to to
data of the nuclear modification factor, for
jet fragment flavors at ATeV c.m. energies
per nucleon pair and with impact parameter fm. A analysis
is presented and shows that data from RHIC and LHC are consistent
with CUJET2.0 at the level for . The
corresponding effective jet transport coefficient
field of this model is computed to facilitate comparison to other jet
tomographic models in the literature. The predicted elliptic asymmetry,
is, however, found to significantly underestimated
relative to RHIC and LHC data. We find the analysis shows that
is very sensitive to allowing even as little as 10\% variations of the
path averaged along in and out of reaction plane paths.Comment: 87 pages, 32 figures; v3: typos corrected, new references and
discussions included; accepted by JHE
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