398 research outputs found
Total Reaction Cross Section in an Isospin-Dependent Quantum Molecular Dynamics (IDQMD) Model
The isospin-dependent quantum molecular dynamics (IDQMD) model is used to
study the total reaction cross section . The energy-dependent Pauli
volumes of neutrons and protons have been discussed and introduced into the
IDQMD calculation to replace the widely used energy-independent Pauli volumes.
The modified IDQMD calculation can reproduce the experimental well
for both stable and exotic nuclei induced reactions. Comparisons of the
calculated induced by with different initial density
distributions have been performed. It is shown that the calculation by using
the experimentally deduced density distribution with a long tail can fit the
experimental excitation function better than that by using the
Skyrme-Hartree-Fock calculated density without long tails. It is also found
that at high energy is sensitive to the long tail of density
distribution.Comment: 4 page, 4 fig
Remarks on self-interaction correction to black hole radiation
In the work [P. Kraus and F. Wilczek, \textit{Self-interaction correction to
black hole radiation, Nucl. Phys.} B433 (1995) 403], it has been pointed out
that the self-gravitation interaction would modify the black hole radiation so
that it is no longer thermal, where it is, however, corrected in an approximate
way and therefore is not established its relationship with the underlying
unitary theory in quantum theory. In this paper, we revisit the
self-gravitation interaction to Hawking radiation of the general spherically
symmetric black hole, and find that the precisely derived spectrum is not only
deviated from the purely thermal spectrum, but most importantly, is related to
the change of the Bekenstein-Hawking entropy and consistent with an underlying
unitary theory.Comment: 14 page
Parallel momentum distribution of the Si fragments from P
Distribution of the parallel momentum of Si fragments from the breakup
of 30.7 MeV/nucleon P has been measured on C targets. The distribution
has the FWHM with the value of 110.5 23.5 MeV/c which is consistent
quantitatively with Galuber model calculation assuming by a valence proton in
P. The density distribution is also predicted by Skyrme-Hartree-Fock
calculation. Results show that there might exist the proton-skin structure in
P.Comment: 4 pages, 4 figure
Back reaction, covariant anomaly and effective action
In the presence of back reaction, we first produce the one-loop corrections
for the event horizon and Hawking temperature of the Reissner-Nordstr\"om black
hole. Then, based on the covariant anomaly cancelation method and the effective
action technique, the modified expressions for the fluxes of gauge current and
energy momentum tensor, due to the effect of back reaction, are obtained. The
results are consistent with the Hawking fluxes of a (1+1)-dimensional blackbody
at the temperature with quantum corrections, thus confirming the robustness of
the covariant anomaly cancelation method and the effective action technique for
black holes with back reaction.Comment: 17 page
Quantum corrections and black hole spectroscopy
In the work \cite{BRM,RBE}, black hole spectroscopy has been successfully
reproduced in the tunneling picture. As a result, the derived entropy spectrum
of black hole in different gravity (including Einstein's gravity,
Einstein-Gauss-Bonnet gravity and Ho\v{r}ava-Lifshitz gravity) are all evenly
spaced, sharing the same forms as , where physical process is only
confined in the semiclassical framework. However, the real physical picture
should go beyond the semiclassical approximation. In this case, the physical
quantities would undergo higher-order quantum corrections, whose effect on
different gravity shares in different forms. Motivated by these facts, in this
paper we aim to observe how quantum corrections affect black hole spectroscopy
in different gravity. The result shows that, in the presence of higher-order
quantum corrections, black hole spectroscopy in different gravity still shares
the same form as , further confirming the entropy quantum is universal
in the sense that it is not only independent of black hole parameters, but also
independent of higher-order quantum corrections. This is a desiring result for
the forthcoming quantum gravity theory.Comment: 14 pages, no figure, use JHEP3.cls. to be published in JHE
The calculation of total reaction cross sections induced by intermediate energy -particles with BUU Model
The Boltzmann-Uehling-Uhlenbeck (BUU) Model, which includes the Fermi motion,
the mean field, individual nucleon-nucleon (N-N) interactions and the Pauli
blocking effect etc., is used to calculate the total reaction cross section
induced by -particles on different targets in the incident
energy range from 17.4 to 48.1 MeV/u. The calculation result can reproduce the
experimental data well. The nucleus-nucleus interaction radius parameter
was extracted from experimental . It is found that becomes
constant with increasing the mass number of target.Comment: 4 pages, 4 fig
Back reaction, emission spectrum and entropy spectroscopy
Recently, an interesting work, which reformulates the tunneling framework to
directly produce the Hawking emission spectrum and entropy spectroscopy in the
tunneling picture, has been received a broad attention. However, during the
emission process, most related observations have not incorporated the effects
of back reaction on the background spacetime, whose derivations are therefore
not the desiring results for the real physical process. With this point as a
central motivation, in this paper we suitably adapt the \emph{reformulated}
tunneling framework so that it can well accommodate the effects of back
reaction to produce the Hawking emission spectrum and entropy spectroscopy.
Consequently, we interestingly find that, when back reaction is considered, the
Parikh-Wilczek's outstanding observations that, an isolated radiating black
hole has an unitary-evolving emission spectrum that is \emph{not} precisely
thermal, but is related to the change of the Bekenstein-Hawking entropy, can
also be reproduced in the reformulated tunneling framework, meanwhile the
entropy spectrum has the same form as that without inclusion of back reaction,
which demonstrates the entropy quantum is \emph{independent} of the effects of
back reaction. As our final analysis, we concentrate on the issues of the black
hole information, but \emph{unfortunately} find that, even including the
effects of back reaction and higher-order quantum corrections, such tunneling
formalism can still not provide a mechanism for preserving the black hole
information.Comment: 16 pages, no figure, use JHEP3.cls. to be published in JHE
Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity
In various astrophysical contexts, we analyze self-similar behaviours of
magnetohydrodynamic (MHD) evolution of a quasi-spherical polytropic magnetized
gas under self-gravity with the specific entropy conserved along streamlines.
In particular, this MHD model analysis frees the scaling parameter in the
conventional polytropic self-similar transformation from the constraint of
with being the polytropic index and therefore
substantially generalizes earlier analysis results on polytropic gas dynamics
that has a constant specific entropy everywhere in space at all time. On the
basis of the self-similar nonlinear MHD ordinary differential equations, we
examine behaviours of the magnetosonic critical curves, the MHD shock
conditions, and various asymptotic solutions. We then construct global
semi-complete self-similar MHD solutions using a combination of analytical and
numerical means and indicate plausible astrophysical applications of these
magnetized flow solutions with or without MHD shocks.Comment: 21 pages, 7 figures, accepted for publication in APS
The Holographic Dark Energy in a Non-flat Universe
We study the model for holographic dark energy in a spatially closed
universe, generalizing the proposal in hep-th/0403127 for a flat universe. We
provide independent arguments for the choice of the parameter in the
holographic dark energy model. On the one hand, can not be less than 1, to
avoid violating the second law of thermodynamics. On the other hand,
observation suggests be very close to 1, it is hard to justify a small
deviation of from 1, if .Comment: 12 pages, harvmac, v2: order of authors is corrected in webpage, v3:
refs. adde
Curvaton Dynamics and the Non-Linearity Parameters in Curvaton Model
We investigate the curvaton dynamics and the non-linearity parameters in
curvaton model with potential slightly deviating from the quadratic form in
detail. The non-linearity parameter will show up due to the curvaton
self-interaction. We also point out that the leading order of non-quadratic
term in the curvaton potential can be negative, for example in the axion-type
curvaton model. If a large positive is detected, the axion-type
curvaton model will be preferred.Comment: 14 pages, 4 figures; refs adde
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