880 research outputs found
Wave dynamics of a six-dimensional black hole localized on a tensional three-brane
We study the quasinormal modes and the late-time tail behavior of scalar
perturbation in the background of a black hole localized on a tensional
three-brane in a world with two large extra dimensions. We find that finite
brane tension modifies the standard results in the wave dynamics for the case
of a black hole on a brane with completely negligible tension. We argue that
the wave dynamics contains the imprint of the extra dimensions.Comment: revised version, 10 pages, 1 table and 2 figures. Accepted for
publication in Phys. Lett.
Nuclear matter and neutron matter for improved quark mass density- dependent model with mesons
A new improved quark mass density-dependent model including u, d quarks,
mesons, mesons and mesons is presented. Employing this
model, the properties of nuclear matter, neutron matter and neutron star are
studied. We find that it can describe above properties successfully. The
results given by the new improved quark mass density- dependent model and by
the quark meson coupling model are compared.Comment: 18 pages, 7 figure
Improved quark mass density- dependent model with quark-sigma meson and quark-omega meson couplings
An improved quark mass density- dependent model with the non-linear scalar
sigma field and the -meson field is presented. We show that the present
model can describe saturation properties, the equation of state, the
compressibility and the effective nuclear mass of nuclear matter under mean
field approximation successfully. The comparison of the present model and the
quark-meson coupling model is addressed.Comment: 15 pages, 6 figure
The Outflow from the Luminous Young Stellar Object IRAS 20126+4104: From 4000 AU to 0.4 pc
We have imaged the outflow from the luminous young stellar object IRAS 20126+4104 (I20126) with the Submillimeter Array in CO (3-2), HCN (4-3), and SiO (5-4) at 1''-2'' resolutions within a radius of ~20'' from the central driving source. Our observations reveal at least three different components of the outflowing gas: (1) A compact (~4000 AU) bipolar outflow toward the central young stellar object. With a dynamical timescale of ~120 yr, this component represents a very new jet/outflow activity in I20126. (2) A collimated outflow with an extent of ~0.2 pc previously detected in SiO (2-1). Both morphology and kinematics favor this component being a jet-driven bow shock system. (3) An S-shaped CO outflow with an extent of ~0.4 pc. This component records the precession history very well. Its kinematic feature, where the velocity increases with distance from the YSO, indicates, independently of other evidence, that the outflow axis is moving toward the plane of the sky. The three outflow components record the history of the primary jet precession over scales ranging from a few hundred AU to approximately 0.4 pc. Our results indicate that CO (3-2) emission is a good tracer to probe the primary jet. The gas densities and SiO relative abundances in I20126 shocks are estimated using the large velocity gradient calculations. The inferred SiO abundances of (1-5) × 10-8 in I20126 outflow lobes are comparable to the expected enhancement at shocked regions
The Hot and Clumpy Molecular Cocoon Surrounding the Ultracompact HII Region G5.89-0.39
We present observations of CH3CN (12-11) emission at a resolution of 2"
toward the shell-like ultracompact HII region G5.89-0.39 with the Submillimeter
Array. The integrated CH3CN emission reveals dense and hot molecular cocoon in
the periphery of the HII region G5.89-0.39, with a CH3CN deficient region
roughly centered at G5.89-0.39. By analyzing the CH3CN emission using
population diagram analysis, we find, for the first time, a decreasing
temperature structure from 150 to 40 K with the projected distance from Feldt's
star, which is thought to be responsible for powering the HII region. Our
results further indicate that the majority of the heating energy in the
observed dense gas is supplied by the Feldt's star. From the derived CH3CN
column density profile, we conclude that the dense gas is not
uniformly-distributed but centrally-concentrated, with a power-law exponent of
5.5 for r < 8000 AU, and 2.0 for 8000 AU < r < 20000 AU, where r is the
distance to Feldt's star. The estimated large power index of 5.5 can be
attributed to an enhancement of CH3CN abundance in the close vicinity of
Feldt's star.Comment: accepted for publication in The Astrophysical Journal Letter
Quark deconfinement phase transition for improved quark mass density-dependent model
By using the finite temperature quantum field theory, we calculate the finite
temperature effective potential and extend the improved quark mass
density-dependent model to finite temperature. It is shown that this model can
not only describe the saturation properties of nuclear matter, but also explain
the quark deconfinement phase transition successfully. The critical temperature
is given and the effect of - meson is addressed.Comment: 18 pages, 7 figure
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