89,152 research outputs found
Charmonium suppression by gluon bremsstrahlung in p-A and A-B collisions
Prompt gluons are an additional source for charmonium suppression in nuclear
collisions, in particular for nucleus-nucleus collisions. These gluons are
radiated as bremsstrahlung in N-N collisions and interact inelastically with
the charmonium states while the nuclei still overlap. The spectra and mean
number of the prompt gluons are calculated perturbatively and the
gluon-Psi inelastic cross section is estimated. The integrated cross sections
for AB --> J/Psi (Psi')X for p-A and A-B collisions and the dependence on
transverse energy for S-U and Pb-Pb can be described quantitatively with some
adjustment of one parameter \sigma(gPsi).Comment: 17 pages of Latex including 10 figure
Transport theory with self-consistent confinement related to the lattice data
The space-time development of a quark-gluon plasma is calculated from a
Vlasov equation for the distribution function of quasiparticles with medium
dependent masses. At each space-time point the masses are calculated
selfconsistently from a gap equation, whose form is determined by the
requirement that in thermal equilibrium and for a range of temperatures the
energy density of the quasi-particle system is identical to the one from
lattice calculations . The numerical solutions of the Vlasov equation display
confinement. Relations to effective theories like that by Friedberg Lee and
Nambu Jona-Lasinio are established.Comment: 9 pages, 12 figure
Constraints on primordial black holes and primeval density perturbations from the epoch of reionization
We investigate the constraint on the abundance of primordial black holes
(PBHs) and the spectral index of primeval density perturbations given by
the ionizing photon background at the epoch of reionization. Within the
standard inflationary cosmogony, we show that the spectral index of the
power-law power spectrum of primeval density perturbations should be 1.27.
Since the universe is still optical thick at the reionization redshift - 8, this constraint is independent of the unknown parameter of reheating
temperature of the inflation. The ionizing photon background from the PBHs can
be well approximated by a power law spectrum , which is
greatly different from those given by models of massive stars and quasars.Comment: 4 pages, 3 eps figues, to be published in ApJ Letter
Calabi-Yau coalgebras
We provide a construction of minimal injective resolutions of simple
comodules of path coalgebras of quivers with relations. Dual to Calabi-Yau
condition of algebras, we introduce the Calabi-Yau condition to coalgebras.
Then we give some descriptions of Calabi-Yau coalgebras with lower global
dimensions. An appendix is included for listing some properties of cohom
functors
Dualities of artinian coalgebras with applications to noetherian complete algebras
A duality theorem of the bounded derived category of quasi-finite comodules
over an artinian coalgebra is established. Let be a noetherian complete
basic semiperfect algebra over an algebraically closed field, and be its
dual coalgebra. If is Artin-Schelter regular, then the local cohomology of
is isomorphic to a shift of twisted bimodule with
a coalgebra automorphism. This yields that the balanced dualinzing
complex of is a shift of the twisted bimodule . If
is an inner automorphism, then is Calabi-Yau
Extrinsic models for the dielectric response of CaCu{3}Ti{4}O{12}
The large, temperature-independent, low-frequency dielectric constant
recently observed in single-crystal CaCu{3}Ti{4}O{12} is most plausibly
interpreted as arising from spatial inhomogenities of its local dielectric
response. Probable sources of inhomogeneity are the various domain boundaries
endemic in such materials: twin, Ca-ordering, and antiphase boundaries. The
material in and neighboring such boundaries can be insulating or conducting. We
construct a decision tree for the resulting six possible morphologies, and
derive or present expressions for the dielectric constant for models of each
morphology. We conclude that all six morphologies can yield dielectric behavior
consistent with observations and suggest further experiments to distinguish
among them.Comment: 9 pages, with 1 postscript figure embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/mc_ext/index.htm
Euler equation of the optimal trajectory for the fastest magnetization reversal of nano-magnetic structures
Based on the modified Landau-Lifshitz-Gilbert equation for an arbitrary
Stoner particle under an external magnetic field and a spin-polarized electric
current, differential equations for the optimal reversal trajectory, along
which the magnetization reversal is the fastest one among all possible reversal
routes, are obtained. We show that this is a Euler-Lagrange problem with
constrains. The Euler equation of the optimal trajectory is useful in designing
a magnetic field pulse and/or a polarized electric current pulse in
magnetization reversal for two reasons. 1) It is straightforward to obtain the
solution of the Euler equation, at least numerically, for a given magnetic
nano-structure characterized by its magnetic anisotropy energy. 2) After
obtaining the optimal reversal trajectory for a given magnetic nano-structure,
finding a proper field/current pulse is an algebraic problem instead of the
original nonlinear differential equation
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