1,812 research outputs found
Absence of continuous spectral types for certain nonstationary random models
We consider continuum random Schr\"odinger operators of the type with a deterministic background potential .
We establish criteria for the absence of continuous and absolutely continuous
spectrum, respectively, outside the spectrum of . The models we
treat include random surface potentials as well as sparse or slowly decaying
random potentials. In particular, we establish absence of absolutely continuous
surface spectrum for random potentials supported near a one-dimensional surface
(``random tube'') in arbitrary dimension.Comment: 14 pages, 2 figure
A quantitative central limit theorem for linear statistics of random matrix eigenvalues
It is known that the fluctuations of suitable linear statistics of Haar
distributed elements of the compact classical groups satisfy a central limit
theorem. We show that if the corresponding test functions are sufficiently
smooth, a rate of convergence of order almost can be obtained using a
quantitative multivariate CLT for traces of powers that was recently proven
using Stein's method of exchangeable pairs.Comment: Title modified; main result stated under slightly weaker conditions;
accepted for publication in the Journal of Theoretical Probabilit
Single Proton Knock-Out Reactions from 24,25,26F
The cross sections of the single proton knock-out reactions from 24F, 25F,
and 26F on a 12C target were measured at energies of about 50 MeV/nucleon.
Ground state populations of 6.6+-.9 mb, 3.8+-0.6 mb for the reactions
12C(24F,23O) and 12C(25F,24O) were extracted, respectively. The data were
compared to calculations based on the many-body shell model and the eikonal
theory. In the reaction 12C(26F,25O) the particle instability of 25O was
confirmed
On the Coulomb-dipole transition in mesoscopic classical and quantum electron-hole bilayers
We study the Coulomb-to-dipole transition which occurs when the separation
of an electron-hole bilayer system is varied with respect to the
characteristic in-layer distances. An analysis of the classical ground state
configurations for harmonically confined clusters with reveals that
the energetically most favorable state can differ from that of two-dimensional
pure dipole or Coulomb systems. Performing a normal mode analysis for the N=19
cluster it is found that the lowest mode frequencies exhibit drastic changes
when is varied. Furthermore, we present quantum-mechanical ground states
for N=6, 10 and 12 spin-polarized electrons and holes. We compute the
single-particle energies and orbitals in self-consistent Hartree-Fock
approximation over a broad range of layer separations and coupling strengths
between the limits of the ideal Fermi gas and the Wigner crystal
Positivity of Lyapunov exponents for a continuous matrix-valued Anderson model
We study a continuous matrix-valued Anderson-type model. Both leading
Lyapunov exponents of this model are proved to be positive and distinct for all
ernergies in except those in a discrete set, which leads to
absence of absolutely continuous spectrum in . This result is an
improvement of a previous result with Stolz. The methods, based upon a result
by Breuillard and Gelander on dense subgroups in semisimple Lie groups, and a
criterion by Goldsheid and Margulis, allow for singular Bernoulli
distributions
Half-life and spin of 60Mn^g
A value of 0.28 +/- 0.02 s has been deduced for the half-life of the ground
state of 60Mn, in sharp contrast to the previously adopted value of 51 +/- 6 s.
Access to the low-spin 60Mn ground state was accomplished via beta decay of the
0+ 60Cr parent nuclide. New, low-energy states in 60Mn have been identified
from beta-delayed gamma-ray spectroscopy. The new, shorter half-life of 60Mn^g
is not suggestive of isospin forbidden beta decay, and new spin and parity
assignments of 1+ and 4+ have been adopted for the ground and isomeric
beta-decaying states, respectively, of 60Mn.Comment: 13 pages, 5 figures, Accepted for publication in Phys. Rev.
Half-life Limit of 19Mg
A search for 19Mg was performed using projectile fragmentation of a 150
MeV/nucleon 36Ar beam. No events of 19Mg were observed. From the time-of-flight
through the fragment separator an upper limit of 22 ns for the half-life of
19Mg was established
Evidence for a change in the nuclear mass surface with the discovery of the most neutron-rich nuclei with 17<Z <25
The results of measurements of the production of neutron-rich nuclei by the
fragmentation of a 76-Ge beam are presented. The cross sections were measured
for a large range of nuclei including fifteen new isotopes that are the most
neutron-rich nuclides of the elements chlorine to manganese (50-Cl, 53-Ar,
55,56-K, 57,58-Ca, 59,60,61-Sc, 62,63-Ti, 65,66-V, 68-Cr, 70-Mn). The enhanced
cross sections of several new nuclei relative to a simple thermal evaporation
framework, previously shown to describe similar production cross sections,
indicates that nuclei in the region around 62-Ti might be more stable than
predicted by current mass models and could be an indication of a new island of
inversion similar to that centered on 31-Na.Comment: 4 pages, 3 figures, to be published in Physical Review Letters, 200
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