529 research outputs found
Applicability of a Representation for the Martin's Real-Part Formula in Model-Independent Analyses
Using a novel representation for the Martin's real-part formula without the
full scaling property, an almost model-independent description of the
proton-proton differential cross section data at high energies (19.4 GeV - 62.5
GeV) is obtained. In the impact parameter and eikonal frameworks, the extracted
inelastic overlap function presents a peripheral effect (tail) above 2 fm and
the extracted opacity function is characterized by a zero (change of sign) in
the momentum transfer space, confirming results from previous model-independent
analyses. Analytical parametrization for these empirical results are introduced
and discussed. The importance of investigations on the inverse problems in
high-energy elastic hadron scattering is stressed and the relevance of the
proposed representation is commented. A short critical review on the use of
Martin's formula is also presented.Comment: Two comments and one reference added at the end of Subsec. 3.3; 23
pages, 9 figures; to be published in Int. J. Mod. Phys.
A Counterexample to Claimed COBE Constraints on Compact Toroidal Universe Models
It has been suggested that if the Universe satisfies a flat, multiply
connected, perturbed Friedmann-Lema^itre model, then cosmic microwave
background data from the COBE satellite implies that the minimum size of the
injectivity diameter (shortest closed spatial geodesic) must be larger than
about two fifths of the horizon diameter. To show that this claim is
misleading, a simple universe model of injectivity diameter a
quarter of this size, i.e. a tenth of the horizon diameter, is shown to be
consistent with COBE four year observational maps of the cosmic microwave
background. This is done using the identified circles principle.Comment: 11 pages, 3 figures, accepted for Classical & Quantum Gravit
On the rise of proton-proton cross-sections at high energies
The rise of the total, elastic and inelastic hadronic cross sections at high
energies is investigated by means of an analytical parametrization, with the
exponent of the leading logarithm contribution as a free fit parameter. Using
derivative dispersion relations with one subtraction, two different fits to
proton-proton and antiproton-proton total cross section and rho parameter data
are developed, reproducing well the experimental information in the energy
region 5 GeV - 7 TeV. The parametrization for the total cross sections is then
extended to fit the elastic (integrated) cross section data in the same energy
region, with satisfactory results. From these empirical results we extract the
energy dependence of several physical quantities: inelastic cross section,
ratios elastic/total, inelastic/total cross sections, ratio
total-cross-section/elastic-slope, elastic slope and optical point. All data,
fitted and predicted, are quite well described. We find a statistically
consistent solution indicating: (1) an increase of the hadronic cross sections
with the energy faster than the log-squared bound by Froissart and Martin; (2)
asymptotic limits 1/3 and 2/3 for the ratios elastic/total and inelastic/total
cross sections, respectively, a result in agreement with unitarity. These
indications corroborate recent theoretical arguments by Ya. I. Azimov on the
rise of the total cross section.Comment: 35 pages, 12 figures, discussions improved with further
clarifications, references added and updated, one note added, results and
conclusions unchanged. Version to be published in J. Phys. G: Nucl. Part.
Phy
Eficiência da utilização do índice multiplicativo TBH na seleção de genótipos de sorgo sacarino.
Casimir energy in a small volume multiply connected static hyperbolic pre-inflationary Universe
A few years ago, Cornish, Spergel and Starkman (CSS), suggested that a
multiply connected ``small'' Universe could allow for classical chaotic mixing
as a pre-inflationary homogenization process. The smaller the volume, the more
important the process. Also, a smaller Universe has a greater probability of
being spontaneously created. Previously DeWitt, Hart and Isham (DHI) calculated
the Casimir energy for static multiply connected flat space-times. Due to the
interest in small volume hyperbolic Universes (e.g. CSS), we generalize the DHI
calculation by making a a numerical investigation of the Casimir energy for a
conformally coupled, massive scalar field in a static Universe, whose spatial
sections are the Weeks manifold, the smallest Universe of negative curvature
known. In spite of being a numerical calculation, our result is in fact exact.
It is shown that there is spontaneous vacuum excitation of low multipolar
components.Comment: accepted for publication in phys. rev.
Characteristic Energy of the Coulomb Interactions and the Pileup of States
Tunneling data on crystals confirm
Coulomb interaction effects through the dependence of the
density of states. Importantly, the data and analysis at high energy, E, show a
pileup of states: most of the states removed from near the Fermi level are
found between ~40 and 130 meV, from which we infer the possibility of universal
behavior. The agreement of our tunneling data with recent photoemission results
further confirms our analysis.Comment: 4 pages, 4 figures, submitted to PR
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