8,696 research outputs found
Basic research on liquid-drop-impact erosion Quarterly report, 8 Dec. 1966 - 8 Mar. 1967
Liquid drop impact erosion - single impact helium driven gas gun, target materials, and elastic wave theory applied to impact of rod
Basic research on liquid-drop-impact erosion
Liquid drop impact erosion in metals and equation for crater dept
Time-Reversal-Violating Schiff Moment of 199Hg
We calculate the Schiff moment of the nucleus 199Hg, created by pi-N-N
vertices that are odd under parity (P) and time-reversal (T). Our approach,
formulated in diagrammatic perturbation theory with important core-polarization
diagrams summed to all orders, gives a close approximation to the expectation
value of the Schiff operator in the odd-A Hartree-Fock-Bogoliubov ground state
generated by a Skyrme interaction and a weak P- and T-odd pion-exchange
potential. To assess the uncertainty in the results, we carry out the
calculation with several Skyrme interactions (the quality of which we test by
checking predictions for the isoscalar-E1 strength distribution in 208Pb) and
estimate most of the important diagrams we omit.Comment: 13 pages, 7 figure
Spin magnetotransport in two-dimensional hole systems
Spin current of two-dimensional holes occupying the ground-state subband in
an asymmetric quantum well and interacting with static disorder potential is
calculated in the presence of a weak magnetic field H perpendicular to the well
plane. Both spin-orbit coupling and Zeeman coupling are taken into account. It
is shown that the applied electric field excites both the transverse
(spin-Hall) and diagonal spin currents, the latter changes its sign at a finite
H and becomes greater than the spin-Hall current as H increases. The effective
spin-Hall conductivity introduced to describe the spin response in Hall bars is
considerably enhanced by the magnetic field in the case of weak disorder and
demonstrates a non-monotonic dependence on H.Comment: 4 pages, 2 figures, published in Phys. Rev.
Neutron-proton pairing in the BCS approach
We investigate the BCS treatment of neutron-proton pairing involving
time-reversed orbits. We conclude that an isospin-symmetric hamiltonian,
treated with the help of the generalized Bogolyubov transformation, fails to
describe the ground state pairing properties correctly. In order for the np
isovector pairs to coexist with the like-particle pairs, one has to break the
isospin symmetry of the hamiltonian by artificially increasing the strength of
np pairing interaction above its isospin symmetric value. We conjecture that
the np isovector pairing represents part (or most) of the congruence energy
(Wigner term) in nuclear masses.Comment: 9 pages, RevTex, submitted to Phys. Rev.
Single- and double-beta decay Fermi-transitions in an exactly solvable model
An exactly solvable model suitable for the description of single and
double-beta decay processes of the Fermi-type is introduced. The model is
equivalent to the exact shell-model treatment of protons and neutrons in a
single j-shell. Exact eigenvalues and eigenvectors are compared to those
corresponding to the hamiltonian in the quasiparticle basis (qp) and with the
results of both the standard quasiparticle random phase approximation (QRPA)
and the renormalized one (RQRPA). The role of the scattering term of the
quasiparticle hamiltonian is analyzed. The presence of an exact eigenstate with
zero energy is shown to be related to the collapse of the QRPA. The RQRPA and
the qp solutions do not include this zero-energy eigenvalue in their spectra,
probably due to spurious correlations. The meaning of this result in terms of
symmetries is presented.Comment: 29 pages, 9 figures included in a Postsript file. Submitted to
Physcal Review
Double beta decay of : the deformed limit
The double beta decay of to the ground state and excited states of
is analysed in the context of the pseudo SU(3) scheme. The results
of this deformed limit are compared with the vibrational one based on the QRPA
formalism. Consistency between the deformed limit and the experimental
information is found for various transitions, although, in this
approximation some energies and B(E2) intensities cannot reproduced.Comment: 16 pages, revtex, no figures. Submmitted to Phys. Rev.
Psychophysiological processes of stress in chronic physical illness: a theoretical perspective
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75576/1/j.1365-2648.1990.tb01843.x.pd
Structure of the vacuum states in the presence of isovector and isoscalar pairing correlations
The long standing problem of proton-neutron pairing and, in particular, the
limitations imposed on the solutions by the available symmetries, is revisited.
We look for solutions with non-vanishing expectation values of the proton, the
neutron and the isoscalar gaps. For an equal number of protons and neutrons we
find two solutions where the absolute values of proton and neutrons gaps are
equal but have the same or opposite sign. The behavior and structure of these
solutions differ for spin saturated (single l-shell) and spin unsaturared
systems (single j-shell). In the former case the BCS results are checked
against an exact calculation.Comment: 19 pages, 5 postscript figure
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