9,671 research outputs found
Classification of BeppoSAX's Gamma-Ray Bursts
The BeppoSAX Catalog has been very recently published. In this paper we
analyze - using the Maximum Likelihood (ML) method - the duration distribution
of the 1003 GRBs listed in the catalog with duration. The ML method can
identify the long and the intermediate duration groups. The short population of
the bursts is identified only at a 96% significance level. MC simulation has
been also applied and gives a similar significance level; 95%. However, the
existence of the short bursts is not a scientific question after the Compton
Gamma-Ray Observatory's observation. Our minor result is this well-known fact
that in the BeppoSAX data the short bursts are underrepresented, mainly caused
by the different triggering system. Our major result is the identification of
the intermediate group in the BeppoSAX data. Therefore, four different
satellites (CGRO, Swift, RHESSI and BeppoSAX) observed the intermediate type
Gamma-Ray Burst.Comment: Accepted for publication in Astrophysics & Space Scienc
The duration distribution of Swift Gamma-Ray Bursts
Decades ago two classes of gamma-ray bursts were identified and delineated as
having durations shorter and longer than about 2 s. Subsequently indications
also supported the existence of a third class. Using maximum likelihood
estimation we analyze the duration distribution of 888 Swift BAT bursts
observed before October 2015. Fitting three log-normal functions to the
duration distribution of the bursts provides a better fit than two log-normal
distributions, with 99.9999% significance. Similarly to earlier results, we
found that a fourth component is not needed. The relative frequencies of the
distribution of the groups are 8% for short, 35% for intermediate and 57% for
long bursts which correspond to our previous results. We analyse the redshift
distribution for the 269 GRBs of the 888 GRBs with known redshift. We find no
evidence for the previously suggested difference between the long and
intermediate GRBs' redshift distribution. The observed redshift distribution of
the 20 short GRBs differs with high significance from the distributions of the
other groups.Comment: accepte
Cosmological Brightness Distribution Fits of Gamma Ray Burst Sources
We discuss detailed fits of the BATSE and PVO gamma-ray burst peak-flux
distributions with Friedman models taking into account possible density
evolution and standard candle or power law luminosity functions. A chi-square
analysis is used to estimate the goodness of the fits and we derive the
significance level of limits on the density evolution and luminosity function
parameters. Cosmological models provide a good fit over a range of parameter
space which is physically reasonable.Comment: Ap.J. in press, uuencoded .ps file, 9 pages manuscript plus 5 figure
Low-dimensional long-range topological structure in the QCD vacuum
Lattice topological charge associated with Ginsparg-Wilson fermions exhibits
generic topological stability over quantum ensemble of configurations
contributing to the QCD path integral. Moreover, the underlying chiral symmetry
leads to the suppression of ultraviolet noise in the associated topological
charge densities ("chiral smoothing"). This provides a solid foundation for the
direct study of the role of topological charge fluctuations in the physics of
QCD vacuum. Using these tools it was recently demonstrated that: (a) there is a
well-defined space-time structure (order) in topological charge density
(defined through overlap fermions) for typical configurations contributing to
QCD path integral; (b) this fundamental structure is low-dimensional,
exhibiting sign-coherent behavior on subsets of dimension less than four and
not less than one; (c) the structure has a long-range global character
(spreading over maximal space-time distances) and is built around the locally
one-dimensional network of strong fields (skeleton). In this talk we elaborate
on certain aspects and implications of these results.Comment: 3 pages, 1 figure; Lattice2003(topology
Macroeconomic implications of virtual shopping : a theoretical approach
Recently, parallel to developments in the communication technology, online shopping has become increasingly popular for many products, like books, CDs, software, and computers. Most analysts conjecture that the future will witness a wider basket of products and a higher trade volume via the Internet. This paper investigates the economic implications of Internet shopping in a Ricardian equilibrium framework. First, it shows the necessary and sufficient condition for the shift to Internet shopping. Next, it indicates that macroeconomic variables like consumption and income rise when this shift takes place. Thus, this paper shows that the economic implications of Internet shopping will be higher than the current experience and Internet shopping will become an important element of the `new economy\' when the bulky part of the shopping is done via the Internet.
Analysis of the BATSE Continuous MER data
The CGRO/BATSE database includes many types of data such as the 16-channel
continuous background or medium energy resolution burst data (CONT and MER data
types). We have calculated some four hundred burst's medium energy resolution
spectra and Principal Component Analysis has been applied. We found five
components can describe GRBs' spectra.Comment: 4 pages, 2 figures, accepted in Nuovo Ciment
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