221,320 research outputs found
Fe/Ni ratio in the Ant Nebula Mz 3
We have analyzed the [Fe II] and [Ni II] emission lines in the bipolar
planetary nebula Mz~3. We find that the [Fe II] and [Ni II] lines arise
exclusively from the central regions. Fluorescence excitation in the formation
process of these lines is negligible for this low-excitation nebula. From the
[Fe II]/[Ni II] ratio, we obtain a higher Fe/Ni abundance ratio with respect to
the solar value. The current result provides further supporting evidence for Mz
3 as a symbiotic Mira.Comment: 2 pages, 1 figure, to be published in the Proceedings of the IAU
Symposium 234: Planetary Nebulae in Our Galaxy and Beyond, eds. M.J. Barlow,
R.H. Mende
Yang-Mills condensate dark energy coupled with matter and radiation
The coincidence problem is studied for the dark energy model of effective
Yang-Mills condensate in a flat expanding universe during the matter-dominated
stage. The YMC energy is taken to represent the dark energy, which
is coupled either with the matter, or with both the matter and the radiation
components. The effective YM Lagrangian is completely determined by quantum
field theory up to 1-loop order. It is found that under very generic initial
conditions and for a variety of forms of coupling, the existence of the scaling
solution during the early stages and the subsequent exit from the scaling
regime are inevitable. The transition to the accelerating stage always occurs
around a redshift . Moreover, when the Yang-Mills
condensate transfers energy into matter or into both matter and radiation, the
equation of state of the Yang-Mills condensate can cross over -1 around
, and takes on a current value . This is consistent with
the recent preliminary observations on supernovae Ia. Therefore, the
coincidence problem can be naturally solved in the effective YMC dark energy
models.Comment: 24 pages, 18 figure
Resonating group method study of kaon-nucleon elastic scattering in the chiral SU(3) quark model
The chiral SU(3) quark model is extended to include an antiquark in order to
study the kaon-nucleon system. The model input parameters , ,
are taken to be the same as in our previous work which focused on the
nucleon-nucleon and nucleon-hyperon interactions. The mass of the scalar meson
is chosen to be 675 MeV and the mixing of and is
considered. Using this model the kaon-nucleon and partial waves phase
shifts of isospin I=0 and I=1 have been studied by solving a resonating group
method (RGM) equation. The numerical results of , , ,
, and partial waves are in good agreement with the
experimental data while the phase shifts of partial wave are a little
bit too repulsive when the laboratory momentum of the kaon meson is greater
than 500 MeV in this present calculation.Comment: 17 pages, 6 figures. Final version for publicatio
Baryon-meson interactions in chiral quark model
Using the resonating group method (RGM), we dynamically study the
baryon-meson interactions in chiral quark model. Some interesting results are
obtained: (1) The Sigma K state has an attractive interaction, which
consequently results in a Sigma K quasibound state. When the channel coupling
of Sigma K and Lambda K is considered, a sharp resonance appears between the
thresholds of these two channels. (2) The interaction of Delta K state with
isospin I=1 is attractive, which can make for a Delta K quasibound state. (3)
When the coupling to the Lambda K* channel is considered, the N phi is found to
be a quasibound state in the extended chiral SU(3) quark model with several MeV
binding energy. (4) The calculated S-, P-, D-, and F-wave KN phase shifts
achieve a considerable improvement in not only the signs but also the
magnitudes in comparison with other's previous quark model study.Comment: 5 pages, 2 figures. Talk given at 3rd Asia Pacific Conference on
Few-Body Problems in Physics (APFB05), Korat, Nakhon Ratchasima, Thailand,
26-30 Jul 200
Possible and Molecular states in a chiral quark model
We perform a systematic study of the bound state problem of and
systems by using effective interaction in our chiral quark model.
Our results show that both the interactions of and states
are attractive, which consequently result in
and bound states.Comment: arXiv admin note: substantial text overlap with arXiv:1204.395
- …