10,735 research outputs found
Heavy-Quarkonium Production in High Energy Proton-Proton Collisions at RHIC
We update the study of the total Psi and Upsilon production cross section in
proton-proton collisions at RHIC energies using the QCD-based Color-Singlet
(CS) Model, including next-to-leading order partonic matrix elements. We also
include charm-quark initiated processes which appear at leading order in
alpha_s, but which have so far been overlooked in such studies. Contrary to
earlier claims, we show that the CS yield is consistent with measurements over
a broad range of J/Psi rapidities. We also find that charm-quark initiated
processes, including both intrinsic and sea-like charm components, typically
contribute at least 20% of the direct J/Psi yield, improving the agreement with
data both for the integrated cross section and its rapidity dependence. The key
signature for such processes is the observation of a charm-quark jet opposite
in azimuthal angle phi to the detected J/Psi. Our results have impact on the
proper interpretation of heavy-quarkonium production in heavy-ion collisions
and its use as a probe for the quark-gluon plasma.Comment: 5 pages, 11 figures, LaTeX, version to appear as a Rapid
Communication in Phys. Rev.
Analysis of video sequences: table of content and index creation
This paper deals with the representation of video sequences useful
for tasks such as long-term analysis, indexing or browsing. A Table
Of Content and index creation algorithm is presented, as well as
additional tools involved in their creation. The proposed method
does not assume any a priori knowledge about the content or the
structure of the video. It is therefore a generic technique. Some
examples are presented in order to assess the performance of the
algorithmPeer ReviewedPostprint (published version
Pure emitter dephasing : a resource for advanced solid-state single photon sources
We have computed the spectrum emitted spontaneously by a quantum dot coupled
to an arbitrarily detuned single mode cavity, taking into account pure
dephasing processes. We show that if the emitter is incoherent, the cavity can
efficiently emit photons with its own spectral characteristics. This effect
opens unique opportunities for the development of devices exploiting both
cavity quantum electrodynamics effects and pure dephasing, such as wavelength
stabilized single photon sources robust against spectral diffusion.Comment: 5 pages, 3 figure
A proposal for impact-adjusted valuation: Critical leverage and execution risk
The practice of valuation by marking-to-market with current trading prices is
seriously flawed. Under leverage the problem is particularly dramatic: due to
the concave form of market impact, selling always initially causes the expected
leverage to increase. There is a critical leverage above which it is impossible
to exit a portfolio without leverage going to infinity and bankruptcy becoming
likely. Standard risk-management methods give no warning of this problem, which
easily occurs for aggressively leveraged positions in illiquid markets. We
propose an alternative accounting procedure based on the estimated market
impact of liquidation that removes the illusion of profit. This should curb the
leverage cycle and contribute to an enhanced stability of financial markets.Comment: 19 pages, 3 figure
Critical reflexivity in financial markets: a Hawkes process analysis
We model the arrival of mid-price changes in the E-Mini S&P futures contract
as a self-exciting Hawkes process. Using several estimation methods, we find
that the Hawkes kernel is power-law with a decay exponent close to -1.15 at
short times, less than approximately 10^3 seconds, and crosses over to a second
power-law regime with a larger decay exponent of approximately -1.45 for longer
times scales in the range [10^3, 10^6] seconds. More importantly, we find that
the Hawkes kernel integrates to unity independently of the analysed period,
from 1998 to 2011. This suggests that markets are and have always been close to
criticality, challenging a recent study which indicates that reflexivity
(endogeneity) has increased in recent years as a result of increased automation
of trading. However, we note that the scale over which market events are
correlated has decreased steadily over time with the emergence of higher
frequency trading.Comment: 9 pages, 6 figures. Some clarification and correction made to section
II, minor alterations elsewher
An alternative approach to efficient simulation of micro/nanoscale phonon transport
Starting from the recently proposed energy-based deviational formulation for
solving the Boltzmann equation [J.-P. Peraud and N. G. Hadjiconstantinou, Phys.
Rev. B 84, 2011], which provides significant computational speedup compared to
standard Monte Carlo methods for small deviations from equilibrium, we show
that additional computational benefits are possible in the limit that the
governing equation can be linearized. The proposed method exploits the
observation that under linearized conditions (small temperature differences)
the trajectories of individual deviational particles can be decoupled and thus
simulated independently; this leads to a particularly simple and efficient
algorithm for simulating steady and transient problems in arbitrary
three-dimensional geometries, without introducing any additional approximation.Comment: 4 pages, 2 figure
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