630 research outputs found
Big-Bang Nucleosynthesis with Unstable Gravitino and Upper Bound on the Reheating Temperature
We study the effects of the unstable gravitino on the big-bang
nucleosynthesis. If the gravitino mass is smaller than \sim 10 TeV, primordial
gravitinos produced after the inflation are likely to decay after the big-bang
nucleosynthesis starts, and the light element abundances may be significantly
affected by the hadro- and photo-dissociation processes as well as by the p n
conversion process. We calculate the light element abundances and derived upper
bound on the reheating temperature after the inflation. In our analysis, we
calculate the decay parameters of the gravitino (i.e., lifetime and branching
ratios) in detail. In addition, we performed a systematic study of the hadron
spectrum produced by the gravitino decay, taking account of all the hadrons
produced by the decay products of the gravitino (including the daughter
superparticles). We discuss the model-dependence of the upper bound on the
reheating temperature.Comment: 32 pages, 11 figure
Confocal microphotoluminescence of InGaN-based light-emitting diodes
Spatially resolved photoluminescence (PL) of InGaN/GaN/AlGaN-based quantum-well-structured light-emitting diodes (LEDs) with a yellow-green light (530 nm) and an amber light (600 nm) was measured by using confocal microscopy. Submicron-scale spatial inhomogeneities of both PL intensities and spectra were found in confocal micro-PL images. We also found clear correlations between PL intensities and peak wavelength for both LEDs. Such correlations for yellow-green and amber LEDs were different from the reported correlations for blue or green LEDs. This discrepancy should be due to different diffusion, localization, and recombination dynamics of electron-hole pairs generated in InGaN active layers, and should be a very important property for influencing the optical properties of LEDs. In order to explain the results, we proposed a possible carrier dynamics model based on the carrier localization and partial reduction of the quantum confinement Stark effect depending on an indium composition in InGaN active layers. By using this model, we also considered the origin of the reduction of the emission efficiencies with a longer emission wavelength of InGaN LEDs with high indium composition
Invariants of Triangular Lie Algebras
Triangular Lie algebras are the Lie algebras which can be faithfully
represented by triangular matrices of any finite size over the real/complex
number field. In the paper invariants ('generalized Casimir operators') are
found for three classes of Lie algebras, namely those which are either strictly
or non-strictly triangular, and for so-called special upper triangular Lie
algebras. Algebraic algorithm of [J. Phys. A: Math. Gen., 2006, V.39, 5749;
math-ph/0602046], developed further in [J. Phys. A: Math. Theor., 2007, V.40,
113; math-ph/0606045], is used to determine the invariants. A conjecture of [J.
Phys. A: Math. Gen., 2001, V.34, 9085], concerning the number of independent
invariants and their form, is corroborated.Comment: LaTeX2e, 16 pages; misprints are corrected, some proofs are extende
Event anisotropy of identified , photon and electron compared to charged , , and deuteron in = 200 GeV Au+Au at PHENIX
We report the recent results of event anisotropy analysis focused on in
= 200 GeV Au+Au collisions at PHENIX.Comment: 4 pages, 3 figures, contribution to the proceedings of the 17th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings
(Journal of Physics G
Direct Photons at RHIC
The PHENIX experiment has measured direct photons in
GeV Au+Au collisions and p+p collisions. The fraction of photons due to direct
production in Au+Au collisions is shown as a function of and centrality.
This measurement is compared with expectation from pQCD calculations. Other
possible sources of direct photons are discussed.Comment: 7 pages, 5 figures, presented at Hot Quarks 2004, Taos, N
Centrality Dependence of Thermal Parameters Deduced from Hadron Multiplicities in Au + Au Collisions at sqrt{s_{NN}} = 130 GeV
We analyse the centrality dependence of thermal parameters deduced from
hadron m ultiplicities in Au + Au collisions at .
While the chemical freeze-out temperature and chemical potentials are found to
be roughly centrality-independent, the strangeness saturation factor
increases with participant number towards unity, supporting the assumption of
equilibrium freeze-out conditions in central collisions
PHENIX Highlights
Recent highlights of measurements by the PHENIX experiment at RHIC are
presented.Comment: 8 pages, 9 figures. Talk at Quark Matter 200
Particle correlations at RHIC from parton coalescence dynamics -- first results
A new dynamical approach that combines covariant parton transport theory with
hadronization channels via parton coalescence and fragmentation is applied to
Au+Au at RHIC. Basic consequences of the simple coalescence formulas, such as
elliptic flow scaling and enhanced proton/pion ratio, turn out to be rather
sensitive to the spacetime aspects of coalescence dynamics.Comment: Contribution to Quark Matter 2004 (January 11-17, 2004, Oakland, CA).
4 pages, 2 EPS figs, IOP style fil
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