12,560 research outputs found
Another solution to the puzzle of the direct photon elliptic flow
The observed large elliptic flow of direct photons is a puzzle in
relativistic heavy ion physics. Our previous work provided a possibility to
this puzzle with the delayed formation of the quark gluon plasma (QGP) in
relativistic heavy ion collisions. In this work, we got the measured transverse
momentum spectra, elliptic flow v2 and triangular flow v3 of direct photons
from Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) energy
\sqrt s_NN = 200 GeV with all centrality classes explained at the same time
without any additional parameter to EPOS3, a hydrodynamic model which can
successfully reproduce hadronic data such as rapidity distributions, transverse
momenta, elliptic flows and triangular flows from variuos collision systems.
The key point is that, EPOS3 has an initial space eccentricity similar to other
models, however, a stronger radial flow and a weaker momentum eccentrcity made
a good description to the flows of both hadrons and direct photons. The created
QGP matter seems discrete than a soup.Comment: 7 pages 8 fig
An Energetic Variational Approach for ion transport
The transport and distribution of charged particles are crucial in the study
of many physical and biological problems. In this paper, we employ an Energy
Variational Approach to derive the coupled Poisson-Nernst-Planck-Navier-Stokes
system. All physics is included in the choices of corresponding energy law and
kinematic transport of particles. The variational derivations give the coupled
force balance equations in a unique and deterministic fashion. We also discuss
the situations with different types of boundary conditions. Finally, we show
that the Onsager's relation holds for the electrokinetics, near the initial
time of a step function applied field
Anisotropic emission of thermal dielectrons from Au+Au collisions at ~GeV with EPOS3
Dileptons, as an electromagnetic probe, are crucial to study the properties
of a Quark-Gluon Plasma (QGP) created in heavy ion collisions. We calculated
the invariant mass spectra and the anisotropic emission of thermal dielectrons
from Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) energy
~GeV based on EPOS3. This approach provides a realistic
(3+1)-dimensional event-by-event viscous hydrodynamic description of the
expanding hot and dense matter with a very particular initial condition, and a
large set of hadron data and direct photons (besides and !) can
be successfully reproduced. Thermal dilepton emission from both the QGP phase
and the hadronic gas are considered, with the emission rates based on Lattice
QCD and a vector meson model, respectively. We find that the computed invariant
mass spectra (thermal contribution + STAR cocktail) can reproduce the measured
ones from STAR at different centralities. Different compared to other model
predictions, the obtained elliptic flow of thermal dileptons is larger than the
STAR measurement referring to all dileptons. We observe a clear centrality
dependence of thermal dilepton not only for elliptic flow but also for
higher orders. At a given centrality, of thermal dileptons decreases
monotonically with for .Comment: 10pages, 12fig
On the Statistical Multiplexing Gain of Virtual Base Station Pools
Facing the explosion of mobile data traffic, cloud radio access network
(C-RAN) is proposed recently to overcome the efficiency and flexibility
problems with the traditional RAN architecture by centralizing baseband
processing. However, there lacks a mathematical model to analyze the
statistical multiplexing gain from the pooling of virtual base stations (VBSs)
so that the expenditure on fronthaul networks can be justified. In this paper,
we address this problem by capturing the session-level dynamics of VBS pools
with a multi-dimensional Markov model. This model reflects the constraints
imposed by both radio resources and computational resources. To evaluate the
pooling gain, we derive a product-form solution for the stationary distribution
and give a recursive method to calculate the blocking probabilities. For
comparison, we also derive the limit of resource utilization ratio as the pool
size approaches infinity. Numerical results show that VBS pools can obtain
considerable pooling gain readily at medium size, but the convergence to large
pool limit is slow because of the quickly diminishing marginal pooling gain. We
also find that parameters such as traffic load and desired Quality of Service
(QoS) have significant influence on the performance of VBS pools.Comment: Accepted by GlobeCom'1
- …