6,781 research outputs found
Predictions for squeezed back-to-back correlations of and in high-energy heavy-ion collisions by event-by-event hydrodynamics
We calculate the squeezed back-to-back correlation (BBC) functions of and for heavy-ion collisions at RHIC and LHC energies, using
()-dimensional hydrodynamics with fluctuating initial conditions. The BBC
functions averaged over event-by-event calculations for many events for the
hydrodynamic sources are smoothed as a function of the particle momentum. For
heavy-ion collisions of Au+Au at GeV, the BBC functions are
larger than those for collisions of Pb+Pb at TeV. The BBC
of may possibly be observed in peripheral collisions at the RHIC and
LHC energies. It is large for the smaller sources of Cu+Cu collisions at
GeV.Comment: 16 pages, 11 figure
Danger-aware Adaptive Composition of DRL Agents for Self-navigation
Self-navigation, referred as the capability of automatically reaching the
goal while avoiding collisions with obstacles, is a fundamental skill required
for mobile robots. Recently, deep reinforcement learning (DRL) has shown great
potential in the development of robot navigation algorithms. However, it is
still difficult to train the robot to learn goal-reaching and
obstacle-avoidance skills simultaneously. On the other hand, although many
DRL-based obstacle-avoidance algorithms are proposed, few of them are reused
for more complex navigation tasks. In this paper, a novel danger-aware adaptive
composition (DAAC) framework is proposed to combine two individually
DRL-trained agents, obstacle-avoidance and goal-reaching, to construct a
navigation agent without any redesigning and retraining. The key to this
adaptive composition approach is that the value function outputted by the
obstacle-avoidance agent serves as an indicator for evaluating the risk level
of the current situation, which in turn determines the contribution of these
two agents for the next move. Simulation and real-world testing results show
that the composed Navigation network can control the robot to accomplish
difficult navigation tasks, e.g., reaching a series of successive goals in an
unknown and complex environment safely and quickly.Comment: 7 pages, 9 figure
Signature of Granular Structures by Single-Event Intensity Interferometry
The observation of a granular structure in high-energy heavy-ion collisions
can be used as a signature for the quark-gluon plasma phase transition, if the
phase transition is first order in nature. We propose methods to detect a
granular structure by the single-event intensity interferometry. We find that
the correlation function from a chaotic source of granular droplets exhibits
large fluctuations, with maxima and minima at relative momenta which depend on
the relative coordinates of the droplet centers. The presence of this type of
maxima and minima of a single-event correlation function at many relative
momenta is a signature for a granular structure and a first-order QCD phase
transition. We further observe that the Fourier transform of the correlation
function of a granular structure exhibits maxima at the relative spatial
coordinates of the droplet centers, which can provide another signature of the
granular structure.Comment: 22 pages, 5 figures, in LaTex, to be published in Physical Review
Pion transverse-momentum spectrum and elliptic anisotropy of partially coherent source
In this letter, we study the pion momentum distribution of a coherent source
and investigate the influences of coherent emission on the pion
transverse-momentum () spectrum and elliptic anisotropy. With a partially
coherent source, constructed by a conventional viscous hydrodynamics model
(chaotic part) and a parameterized expanding coherent source model, we
reproduce the pion spectrum and elliptic anisotropy coefficient
in the peripheral Pb-Pb collisions at TeV. It
is found that the influences of coherent emission on the pion spectrum
and are related to the initial size and shape of the coherent
source, largely due to the interference effect. However, the effect of source
dynamical evolution on coherent emission is relatively small. The results of
the partially coherent source with 33% coherent emission and 67% chaotic
emission are consistent with the experimental measurements of the pion
spectrum, , and especially four-pion Bose-Einstein correlations.Comment: 8 pages, 4 figure
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