37,512 research outputs found
Information of Structures in Galaxy Distribution
We introduce an information-theoretic measure, the Renyi information, to
describe the galaxy distribution in space. We discuss properties of the
information measure, and demonstrate its relationship with the probability
distribution function and multifractal descriptions. Using the First Look
Survey galaxy samples observed by the Infrared Array Camera onboard Spitzer
Space Telescope, we present measurements of the Renyi information, as well as
the counts-in-cells distribution and multifractal properties of galaxies in
mid-infrared wavelengths. Guided by multiplicative cascade simulation based on
a binomial model, we verify our measurements, and discuss the spatial selection
effects on measuring information of the spatial structures. We derive structure
scan functions at scales where selection effects are small for the Spitzer
samples. We discuss the results, and the potential of applying the Renyi
information to measuring other spatial structures.Comment: 25 pages, 8 figures, submitted to ApJ; To appear in The Astrophysical
Journal 2006, 644, 678 (June 20th
Nuclear modification factor in intermediate-energy heavy-ion collisions
The transverse momentum dependent nuclear modification factors (NMF), namely
, is investigated for protons produced in Au + Au at 1 GeV within
the framework of the isospin-dependent quantum molecular dynamics (IQMD) model.
It is found that the radial collective motion during the expansion stage
affects the NMF at low transverse momentum a lot. By fitting the transverse
mass spectra of protons with the distribution function from the Blast-Wave
model, the magnitude of radial flow can be extracted. After removing the
contribution from radial flow, the can be regarded as a thermal one
and is found to keep unitary at transverse momentum lower than 0.6 GeV/c and
enhance at higher transverse momentum, which can be attributed to Cronin
effect.Comment: 8 pages, 5 figures; aceepted by Physics Letters
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