3,468 research outputs found
Pair loading in Gamma-Ray Burst Fireball And Prompt Emission From Pair-Rich Reverse Shock
Gamma-ray bursts (GRBs) are believed to originate from ultra-relativistic
winds/fireballs to avoid the "compactness problem". However, the most energetic
photons in GRBs may still suffer from absorption leading to
electron/positron pair production in the winds/fireballs. We show here that in
a wide range of model parameters, the resulting pairs may dominate those
electrons associated with baryons. Later on, the pairs would be carried into a
reverse shock so that a shocked pair-rich fireball may produce a strong flash
at lower frequencies, i.e. in the IR band, in contrast with optical/UV emission
from a pair-poor fireball. The IR emission would show a 5/2 spectral index due
to strong self-absorption. Rapid responses to GRB triggers in the IR band would
detect such strong flashes. The future detections of many IR flashes will infer
that the rarity of prompt optical/UV emissions is in fact due to dust
obscuration in the star formation regions.Comment: 8 pages, 2 figures, ApJ accepte
Forecasting Housing Prices under Different Submarket Assumptions
This research evaluated forecasting accuracy of hedonic price models based on a number of different submarket assumptions. Using home sale data for the City of Knoxville and vicinities merged with geographic information, we found that forecasting housing prices with submarkets defined using expert knowledge and by school district and combining information conveyed in different modeling strategies are more accurate and efficient than models that are spatially aggregated, or with submarkets defined by statistical clustering techniques. This finding provided useful implications for housing price prediction in an urban setting and surrounding areas in that forecasting models based on expert knowledge of market structure or public school quality and simple model combining techniques may outperform the models using more sophisticated statistical techniques.Clustering, Forecasting, Hedonic price, Housing Submarket, Demand and Price Analysis, C53, R21,
A Theory of Equivalent Expectation Measures for Contingent Claim Returns
This paper introduces a dynamic change of measure approach for computing the
analytical solutions of expected future prices (and therefore, expected
returns) of contingent claims over a finite horizon. The new approach
constructs hybrid probability measures called the "equivalent expectation
measures"(EEMs), which provide the physical expectation of the claim's future
price until before the horizon date, and serve as pricing measures on or after
the horizon date. The EEM theory can be used for empirical investigations of
both the cross-section and the term structure of returns of contingent claims,
such as Treasury bonds, corporate bonds, and financial derivatives
Cortical plasticity as a new endpoint measurement for chronic pain
Animal models of chronic pain are widely used to investigate basic mechanisms of chronic pain and to evaluate potential novel drugs for treating chronic pain. Among the different criteria used to measure chronic pain, behavioral responses are commonly used as the end point measurements. However, not all chronic pain conditions can be easily measured by behavioral responses such as the headache, phantom pain and pain related to spinal cord injury. Here I propose that cortical indexes, that indicate neuronal plastic changes in pain-related cortical areas, can be used as endpoint measurements for chronic pain. Such cortical indexes are not only useful for those chronic pain conditions where a suitable animal model is lacking, but also serve as additional screening methods for potential drugs to treat chronic pain in humans. These cortical indexes are activity-dependent immediate early genes, electrophysiological identified plastic changes and biochemical assays of signaling proteins. It can be used to evaluate novel analgesic compounds that may act at peripheral or spinal sites. I hope that these new cortical endpoint measurements will facilitate our search for new, and more effective, pain medicines, and help to reduce false lead drug targets
Quantum generalized Reed-Solomon codes: Unified framework for quantum MDS codes
We construct a new family of quantum MDS codes from classical generalized
Reed-Solomon codes and derive the necessary and sufficient condition under
which these quantum codes exist. We also give code bounds and show how to
construct them analytically. We find that existing quantum MDS codes can be
unified under these codes in the sense that when a quantum MDS code exists,
then a quantum code of this type with the same parameters also exists. Thus as
far as is known at present, they are the most important family of quantum MDS
codes.Comment: 9 pages, no figure
Scheme for sharing classical information via tripartite entangled states
We investigate schemes for quantum secret sharing and quantum dense coding
via tripartite entangled states. We present a scheme for sharing classical
information via entanglement swapping using two tripartite entangled GHZ
states. In order to throw light upon the security affairs of the quantum dense
coding protocol, we also suggest a secure quantum dense coding scheme via W
state in analogy with the theory of sharing information among involved users.Comment: 4 pages, no figure. A complete rewrritten vession, accepted for
publication in Chinese Physic
Message passing for task redistribution on sparse graphs
The problem of resource allocation in sparse graphs with real variables is studied using methods of statistical physics. An efficient distributed algorithm is devised on the basis of insight gained from the analysis and is examined using numerical simulations, showing excellent performance and full agreement with the theoretical results
Resource allocation in sparse graphs
Resource allocation in sparsely connected networks, a representative problem of systems with real variables, is studied using the replica and Bethe approximation methods. An efficient distributed algorithm is devised on the basis of insights gained from the analysis and is examined using numerical simulations,showing excellent performance and full agreement with the theoretical results. The physical properties of the resource allocation model are discussed
Unraveling the exciton binding energy and the dielectric constant in single crystal methylammonium lead tri-iodide perovskite
We have accurately determined the exciton binding energy and reduced mass of
single crystals of methylammonium lead tri-iodide using magneto-reflectivity at
very high magnetic fields. The single crystal has excellent optical properties
with a narrow line width of meV for the excitonic transitions and a 2s
transition which is clearly visible even at zero magnetic field. The exciton
binding energy of meV in the low temperature orthorhombic phase is
almost identical to the value found in polycrystalline samples, crucially
ruling out any possibility that the exciton binding energy depends on the grain
size. In the room temperature tetragonal phase, an upper limit for the exciton
binding energy of meV is estimated from the evolution of 1s-2s
splitting at high magnetic field.Comment: 5 pages, 4 figure
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