18,588 research outputs found
Charge Transfer Fluctuations as a QGP Signal
In this study, we analyze the recently proposed charge transfer fluctuations
within a finite pseudo-rapidity space. As the charge transfer fluctuation is a
measure of the local charge correlation length, it is capable of detecting
inhomogeneity in the hot and dense matter created by heavy ion collisions. We
predict that going from peripheral to central collisions, the charge transfer
fluctuations at midrapidity should decrease substantially while the charge
transfer fluctuations at the edges of the observation window should decrease by
a small amount. These are consequences of having a strongly inhomogeneous
matter where the QGP component is concentrated around midrapidity. We also show
how to constrain the values of the charge correlations lengths in both the
hadronic phase and the QGP phase using the charge transfer fluctuations.
Current manuscript is based on the preprints hep-ph/0503085 (to appear in
Physical Review C) and nucl-th/0506025.Comment: To appear in the proceedings of 18th International Conference on
Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005),
Budapest, Hungary, 4-9 Aug 200
Cooperative Caching for Multimedia Streaming in Overlay Networks
Traditional data caching, such as web caching, only focuses on how to boost the hit rate of requested objects in caches, and therefore, how to reduce the initial delay for object retrieval. However, for multimedia objects, not only reducing the delay of object retrieval, but also provisioning reasonably stable network bandwidth to clients, while the fetching of the cached objects goes on, is important as well. In this paper, we propose our cooperative caching scheme for a multimedia delivery scenario, supporting a large number of peers over peer-to-peer overlay networks. In order to facilitate multimedia streaming and downloading service from servers, our caching scheme (1) determines the appropriate availability of cached stream segments in a cache community, (2) determines the appropriate peer for cache replacement, and (3) performs bandwidth-aware and availability-aware cache replacement. By doing so, it achieves (1) small delay of stream retrieval, (2) stable bandwidth provisioning during retrieval session, and (3) load balancing of clients' requests among peers
Quantile-based bias correction and uncertainty quantification of extreme event attribution statements
Extreme event attribution characterizes how anthropogenic climate change may
have influenced the probability and magnitude of selected individual extreme
weather and climate events. Attribution statements often involve quantification
of the fraction of attributable risk (FAR) or the risk ratio (RR) and
associated confidence intervals. Many such analyses use climate model output to
characterize extreme event behavior with and without anthropogenic influence.
However, such climate models may have biases in their representation of extreme
events. To account for discrepancies in the probabilities of extreme events
between observational datasets and model datasets, we demonstrate an
appropriate rescaling of the model output based on the quantiles of the
datasets to estimate an adjusted risk ratio. Our methodology accounts for
various components of uncertainty in estimation of the risk ratio. In
particular, we present an approach to construct a one-sided confidence interval
on the lower bound of the risk ratio when the estimated risk ratio is infinity.
We demonstrate the methodology using the summer 2011 central US heatwave and
output from the Community Earth System Model. In this example, we find that the
lower bound of the risk ratio is relatively insensitive to the magnitude and
probability of the actual event.Comment: 28 pages, 4 figures, 3 table
Formulating the Net Gain of MISO-SFN in the Presence of Self-Interferences
In this study, an analytical formula for multiple-input single-output single frequency network gain (MISO-SFNG) is investigated. To formulate the net MISO-SFNG, we derived the average signal to interference plus noise ratio (SINR) where the gain achieved by the distributed MISO diversity as a function of power imbalance is curve-fitted. Further, we analyzed the losses owing to self-interferences resulting from the delay spread and imperfect channel estimation. We verified the accuracy and effectiveness of the derived formula by comparing the measurement results with the analytical results. The derived formula helps to understand how various system factors affect the gain under a given condition. The formula can be used to evaluate the MISO-SFNG and to predict the MISO-SFN coverage in various system configurations
Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion
Anomalous diffusion is frequently described by scaled Brownian motion (SBM),
a Gaussian process with a power-law time dependent diffusion coefficient. Its
mean squared displacement is with
for . SBM may provide a
seemingly adequate description in the case of unbounded diffusion, for which
its probability density function coincides with that of fractional Brownian
motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a
significant amplitude scatter of the time averaged mean squared displacement.
More severely, we demonstrate that under confinement, the dynamics encoded by
SBM is fundamentally different from both fractional Brownian motion and
continuous time random walks. SBM is highly non-stationary and cannot provide a
physical description for particles in a thermalised stationary system. Our
findings have direct impact on the modelling of single particle tracking
experiments, in particular, under confinement inside cellular compartments or
when optical tweezers tracking methods are used.Comment: 7 pages, 5 figure
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