26,397 research outputs found
Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules
For each integer , we demonstrate that a -dimensional
generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry
which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of
bound states is shown to form a unitary highest weight \mr{Spin}(2,
2n+2)-module which occurs at the first reduction point in the
Enright-Howe-Wallach classification diagram for the unitary highest weight
modules. As a byproduct, we get a simple geometric realization for such a
unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update
Antimagnetic Rotation Band in Nuclei: A Microscopic Description
Covariant density functional theory and the tilted axis cranking method are
used to investigate antimagnetic rotation (AMR) in nuclei for the first time in
a fully self-consistent and microscopic way. The experimental spectrum as well
as the B(E2) values of the recently observed AMR band in 105Cd are reproduced
very well. This gives a further strong hint that AMR is realized in specific
bands in nuclei.Comment: 10 pages, 4 figure
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions. II. Microscopic analysis of low-lying states in magnesium isotopes
The recently developed structure model that uses the generator coordinate
method to perform configuration mixing of angular-momentum projected wave
functions, generated by constrained self-consistent relativistic mean-field
calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study
of ground states and low-energy collective states in the even-even magnesium
isotopes Mg. Results obtained using a relativistic point-coupling
nucleon-nucleon effective interaction in the particle-hole channel, and a
density-independent -interaction in the pairing channel, are compared
to data and with previous axial 1DAMP+GCM calculations, both with a
relativistic density functional and the non-relativistic Gogny force. The
effects of the inclusion of triaxial degrees of freedom on the low-energy
spectra and E2 transitions of magnesium isotopes are examined.Comment: 28 pages, 11 figures and 1 tabl
Covariant density functional theory for antimagnetic rotation
Following the previous letter on the first microscopic description of the
antimagnetic rotation (AMR) in 105Cd, a systematic investigation and detailed
analysis for the AMR band in the frame-work of tilted axis cranking (TAC) model
based on covariant density functional theory are carried out. After performing
the microscopic and self-consistentTAC calculations with an given density
functional, the configuration for the observed AMR band in 105Cd is obtained
from the single-particle Routhians. With the configuration thus obtained, the
tilt angle for a given rotational frequency is determined self-consistently by
minimizing the total Routhian with respect to the tilt angle. In such a way,
the energy spectrum, total angular momenta, kinetic and dynamic moments of
inertia, and the B(E2) values for the AMR band in 105Cd are calculated. Good
agreement with the data is found. By investigating microscopically the
contributions from neutrons and protons to the total angular momentum, the
"two-shears-like" mechanism in the AMR band is clearly illus-trated. Finally,
the currents leading to time-odd mean fields in the Dirac equation are
presented and discussed in detail. It is found that they are essentially
determined by the valence particles and/or holes. Their spatial distribution
and size depend onthe specific single-particle orbitals and the rotational
frequency.Comment: 35 pages, 17 figures, accepted by Phys. Rev.
Local covariant density functional constrained by the relativistic Hartree-Fock theory
The recent progress in the localized covariant density functional constrained
by the relativistic Hartree-Fock theory is briefly presented by taking the
Gamow-Teller resonance in 90Zr as an example. It is shown that the constraints
introduced by the Fock terms into the particle-hole residual interactions are
straight forward and robust.Comment: 4 pages, 1 figure, Proceedings of NSD12, Opatija, Croatia, 9-13 July
201
Experimental analysis of IMEP in a rotary combustion engine
A real time indicated mean effective pressure measurement system is described which is used to judge proposed improvements in cycle efficiency of a rotary combustion engine. This is the first self-contained instrument that is capable of making real time measurements of IMEP in a rotary engine. Previous methods used require data recording and later processing using a digital computer. The unique features of this instrumentation include its ability to measure IMEP on a cycle by cycle, real time basis and the elimination of the need to differentiate volume function in real time. Measurements at two engine speeds (2000 and 3000 rpm) and a full range of loads are presented, although the instrument was designed to operate to speeds of 9000 rpm
Effect of pairing correlations on nuclear low-energy structure: BCS and general Bogoliubov transformation
Low-lying nuclear states of Sm isotopes are studied in the framework of a
collective Hamiltonian based on covariant energy density functional theory.
Pairing correlation are treated by both BCS and Bogoliubov methods. It is found
that the pairing correlations deduced from relativistic Hartree-Bogoliubov
(RHB) calculations are generally stronger than those by relativistic mean-field
plus BCS (RMF+BCS) with same pairing force. By simply renormalizing the pairing
strength, the diagonal part of the pairing field is changed in such a way that
the essential effects of the off-diagonal parts of the pairing field neglected
in the RMF+BCS calculations can be recovered, and consequently the low-energy
structure is in a good agreement with the predictions of the RHB model.Comment: 5 figures, 5 page
Preliminary results on performance testing of a turbocharged rotary combustion engine
The performance of a turbocharged rotary engine at power levels above 75 kW (100 hp) was studied. A twin rotor turbocharged Mazda engine was tested at speeds of 3000 to 6000 rpm and boost pressures to 7 psi. The NASA developed combustion diagnostic instrumentation was used to quantify indicated and pumping mean effect pressures, peak pressure, and face to face variability on a cycle by cycle basis. Results of this testing showed that a 5900 rpm a 36 percent increase in power was obtained by operating the engine in the turbocharged configuration. When operating with lean carburetor jets at 105 hp (78.3 kW) and 4000 rpm, a brake specific fuel consumption of 0.45 lbm/lb-hr was measured
Rapid structural change in low-lying states of neutron-rich Sr and Zr isotopes
The rapid structural change in low-lying collective excitation states of
neutron-rich Sr and Zr isotopes is tudied by solving a five-dimensional
collective Hamiltonian with parameters determined by both relativistic
mean-field and non-relativistic Skyrme-Hartree-Fock calculations using the
PC-PK1 and SLy4 forces respectively. Pair correlations are treated in BCS
method with either a separable pairing force or a density-dependent zero-range
force. The isotope shifts, excitation energies, electric monopole and
quadrupole transition strengths are calculated and compared with corresponding
experimental data. The calculated results with both the PC-PK1 and SLy4 forces
exhibit a picture of spherical-oblate-prolate shape transition in neutron-rich
Sr and Zr isotopes. Compared with the experimental data, the PC-PK1 (or SLy4)
force predicts a more moderate (or dramatic) change in most of the collective
properties around N=60. The underlying microscopic mechanism responsible for
the rapid transition is discussed.Comment: 10 pages (twocolumn), 10 figure
Primordial Black Hole Formation from Inflaton
Measurements of the distances to SNe Ia have produced strong evidence that
the Universe is really accelarating, implying the existence of a nearly uniform
component of dark energy with the simplest explanation as a cosmological
constant. In this paper a small changing cosmological term is proposed, which
is a function of a slow-rolling scalar field, by which the de Sitter primordial
black holes' properties, for both charged and uncharged cases, are carefully
examined and the relationship between the black hole formation and the energy
transfer of the inflaton within this cosmological term is eluciatedComment: 6 pages, Late
- …