94,203 research outputs found
Antikaon flow in heavy-ion collisions: the effects of absorption and mean fields
We study antikaon flow in heavy-ion collisions at SIS energies based on the
relativistic transport model (RVUU 1.0). The production of antikaons from both
baryon-baryon and pion-baryon collisions are included. Taking into account only
elastic and inelastic collisions of the antikaon with nucleons and neglecting
its mean-field potential as in the cascade model, a strong antiflow or
anti-correlation of antikaons with respect to nucleons is seen as a result of
the strong absorption of antikaons by nucleons. However, the antiflow of
antikaons disappears after including also their propagation in the attractive
mean-field potential. The experimental measurement of antikaon flow in
heavy-ion collision will be very useful in shedding lights on the relative
importance of antikaon absorption versus its mean-field potential.Comment: 12 pages, 2 postscript figures omitted in the original submission are
included, to appear in Phys. Rev.
Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon
Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon is studied in
the relativistic Vlasov-Uehling-Uhlenbeck model. The self-energies of the
antiproton are determined from the nucleon self-energies by the G-parity
transformation. Also, the final-state interactions of the antiproton including
both rescattering and annihilation are explicitly treated. With a soft nuclear
equation of state, the calculated antiproton momentum spectrum is in good
agreement with recent experimental data from the heavy-ion synchrotron at GSI.
The effect due to the reduced nucleon and antinucleon masses in a medium is
found to be more appreciable than in earlier Bevalac experiments with lighter
systems and at higher energies.Comment: 10 pages, 4 figures available upon request to [email protected].
TAMUNT-940
Interacting non-minimally coupled canonical, phantom and quintom models of holographic dark energy in non-flat universe
Motivated by our recent work \cite{set1}, we generalize this work to the
interacting non-flat case. Therefore in this paper we deal with canonical,
phantom and quintom models, with the various fields being non-minimally coupled
to gravity, within the framework of interacting holographic dark energy. We
employ the holographic model of interacting dark energy to obtain the equation
of state for the holographic energy density in non-flat (closed) universe
enclosed by the event horizon measured from the sphere of horizon named .Comment: 18 pages, 3 figures. Accepted for publication in IJMPD (2010
Weak gravity conjecture constraints on inflation
We consider the gravitational correction to the coupling of the scalar
fields. Weak gravity conjecture says that the gravitational correction to the
running of scalar coupling should be less than the contribution from scalar
fields. For instance, a new scale sets a UV cutoff
on the validity of the effective theory. Furthermore, this
conjecture implies a possible constraint on the inflation model, e.g. the
chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added
and the final version for publication in JHE
Enhancement of low-mass dileptons in SPS heavy-ion collisions: possible evidence for dropping rho meson mass in medium
Dilepton production in proton- and nucleus-induced reactions at SPS energies
is studied in the relativistic transport model using initial conditions
determined by the string dynamics from RQMD. It is found that both the CERES
and HELIOS-3 data for dilepton spectra in proton-nucleus reactions can be well
described by the conventional mechanism of Dalitz decay and direct vector meson
decay. However, to provide a quantitative explanation of the observed dilepton
spectra in central S+Au and S+W collisions requires contributions other than
these direct decays. Introducing a decrease of vector meson masses in hot dense
medium, we find that these heavy-ion data can also be satisfactorily explained.
We also give predictions for Pb+Au collisions at 160 GeV/nucleon using current
CERES mass resolution and acceptance.Comment: 8 pages, LaTeX, figures available from [email protected],
contribution to QM'96, to appear in the proceeding
An Implication of "Gravity as the Weakest Force"
The negative specific heat of a radiating black hole is indicative of a
cataclysmic endpoint to the evaporation process. In this letter, we suggest a
simple mechanism for circumventing such a dramatic outcome. The basis for our
argument is a conjecture that was recently proposed by Arkani-Hamed and
collaborators. To put it another way, we use their notion of ``Gravity as the
Weakest Force'' as a means of inhibiting the process of black hole evaporation.Comment: 7 pages; v2 some discussion clarifie
Medium Dependence of the Vector-Meson Mass: Dynamical and/or Brown-Rho Scaling?
We discuss the similarities and differences for the theories of Rapp, Wambach
and collaborators (called R/W in short) and those based on Brown-Rho scaling
(called B/R), as applied to reproduce the dileptons measured by the CERES
collaboration in the CERN experiments. In both theories the large number of
dileptons at invariant masses ~ are shown to be chiefly
produced by a density-dependent -meson mass. In R/W the medium dependence
is dynamically calculated using hadronic variables defined in the matter-free
vacuum. In B/R scaling it follows from movement towards chiral symmetry
restoration due to medium-induced vacuum change, and is described in terms of
constituent (or quasiparticle) quarks. We argue that the R/W description should
be reliable up to densities somewhat beyond nuclear density, where hadrons are
the effective variables. At higher density there should be a crossover to
constituent quarks as effective variables scaling according to B/R. In the
crossover region, the two descriptions must be ``dual''.Comment: 13 pages LaTeX, incl. 5 eps-figures and appb.sty; Talk given at the
Workshop on 'The Structure of Mesons, Baryons and Nuclei', Cracow, May 1998,
in honor of J. Speth's 60th birthday, to be published in Acta Physica
Polonica
The Measure for the Multiverse and the Probability for Inflation
We investigate the measure problem in the framework of inflationary
cosmology. The measure of the history space is constructed and applied to
inflation models. Using this measure, it is shown that the probability for the
generalized single field slow roll inflation to last for e-folds is
suppressed by a factor , and the probability for the generalized
-field slow roll inflation is suppressed by a much larger factor
. Some non-inflationary models such as the cyclic model do not
suffer from this difficulty.Comment: 16 page
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