689 research outputs found
Structural behavior of uranium dioxide under pressure by LSDA+U calculations
The structural behavior of UO2 under high pressure up to 300GPa has been
studied by first-principles calculations with LSDA+U approximation. The results
show that a pressure-induced structural transition to the cotunnite-type
(orthorhombic Pnma) phase occurs at 38GPa. It agrees well with the
experimentally observed ~42 GPa. An isostructural transition following that is
also predicted to take place from 80 to 130GPa, which has not yet been observed
in experiments. Further high compression beyond 226GPa will result in a
metallic and paramagnetic transition. It corresponds to a volume of 90A^3 per
cell, in good agreement with a previous theoretical analysis in the reduction
of volume required to delocalize 5f states.Comment: 10 pages, 8 figure
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
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
THERMUS -- A Thermal Model Package for ROOT
THERMUS is a package of C++ classes and functions allowing
statistical-thermal model analyses of particle production in relativistic
heavy-ion collisions to be performed within the ROOT framework of analysis.
Calculations are possible within three statistical ensembles; a grand-canonical
treatment of the conserved charges B, S and Q, a fully canonical treatment of
the conserved charges, and a mixed-canonical ensemble combining a canonical
treatment of strangeness with a grand-canonical treatment of baryon number and
electric charge. THERMUS allows for the assignment of decay chains and detector
efficiencies specific to each particle yield, which enables sensible fitting of
model parameters to experimental data.Comment: to be published in Computer Physics Communication
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