5,685 research outputs found
Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions
[Background] Various cluster states of astrophysical interest are expected to
exist in the excited states of . However, they have not been
identified firmly, because of the experimental and theoretical difficulties.
[Purpose] To establish the Mg+, O+C and
Ne+2 cluster bands, we theoretically search for the
negative-parity cluster bands that are paired with the positive-parity bands to
constitute the inversion doublets. We also offer the isoscalar monopole and
dipole transitions as a promising probe for the clustering. We numerically show
that these transition strengths from the ground state to the cluster states are
very enhanced. [Method] The antisymmetrized molecular dynamics with Gogny D1S
effective interaction is employed to calculate the excited states of . The isoscalar monopole and dipole transition strengths are directly
evaluated from wave functions of the ground and excited states. [Results]
Negative-parity bands having Mg+ and O+C cluster
configurations are obtained in addition to the newly calculated
Ne+2 cluster bands. All of them are paired with the
corresponding positive-parity bands to constitute the inversion doublets with
various cluster configurations. The calculation show that the band-head of the
Mg+ and Ne+2 cluster bands are strongly excited
by the isoscalar monopole and dipole transitions. [Conclusions] The present
calculation suggests the existence of the inversion doublets with the
Mg+, O+C and Ne+2
configurations.Because of the enhanced transition strengths, we offer the
isoscalar monopole and dipole transitions as good probe for the
Mg+ and Ne+2 cluster bands.Comment: 28 pages, 8 figure
3alpha clustering in the excited states of 16C
The alpha cluster states of 16C are investigated by using the antisymmetrized
molecular dynamics. It is shown that two different types of alpha cluster
states exist: triangular and linear-chain states. The former has an approximate
isosceles triangular configuration of alpha particles surrounded by four
valence neutrons occupying sd-shell, while the latter has the linearly aligned
alpha particles with two sd-shell neutrons and two pf-shell neutrons. It is
found that the structure of the linear-chain state is qualitatively understood
in terms of the 3/2 pi- and 1/2 sigma- molecular orbit as predicted by
molecular-orbital model, but there exists non-negligible Be+alpha+2n
correlation. The band-head energies of the triangular and linear-chain
rotational bands are 8.0 and 15.5 MeV, and the latter is close to the He+Be
threshold energy. It is also shown that the linear-chain state becomes the
yrast sstate at J=10 with excitation energy 27.8 MeV owing to its very large
moment-of-inertia comparable with hyperdeformation.Comment: 7 pages, 5 figure
Properties of hadron and quark matter studied with a molecular dynamics
We study the hadron-quark phase transition in a molecular dynamics (MD) of
quark degrees of freedom. The hadron state at low density and temperature, and
the deconfined quark state at high density and temperature are observed in our
model. We investigate the equations of state and draw the phase-diagram at wide
baryon density and temperature range. We also discuss the transport property,
e.g. viscosity, of matter. It is found that the ratio of the shear
viscosity to the entropy density is less than one for quark matter.Comment: Poster presentation at Quark Matter 200
Three-dimensional orbits of metal-poor halo stars and the formation of the Galaxy
We present the three-dimensional orbital motions of metal-poor stars in
conjunction with their metal abundances, for the purpose of getting insight
into the formation process of the Galaxy. Our sample stars, which include
metal-deficient red giants and RR Lyrae variables observed by the Hipparcos
satellite, are least affected by known systematics, stemmed from kinematic
bias, metallicity calibration, and secondary metal contamination of stellar
surface. We find, for the stars in the metallicity range of [Fe/H]<-1, that
there is no evidence for the correlation between [Fe/H] and their orbital
eccentricities e. Even for [Fe/H]<-1.6, about 16% of the stars have e less than
0.4. We show that the e distribution of orbits for [Fe/H]<-1.6 is independent
of the height |z| away from the Galactic plane, whereas for [Fe/H]>-1.6 the
stars at |z|>1 kpc are systematically devoid of low-e orbits with e<0.6. This
indicates that low-e stars with [Fe/H]<-1.6 belong to the halo component,
whereas the rapidly-rotating thick disk with a scale height about 1 kpc has a
metal-weak tail in the range of -1.6<[Fe/H]<-1. The fraction of this metal-weak
thick disk appears to be only less than 20%. The significance of these results
for the early evolution of the Galaxy is briefly discussed.Comment: 11 pages, 3 figures, AASTeX, to appear in ApJ Letter
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