1,138 research outputs found
Microscopic mass formulae
By assuming the existence of a pseudopotential smooth enough to do
Hartree-Fock variations and good enough to describe nuclear structure, we
construct mass formulae that rely on general scaling arguments and on a
schematic reading of shell model calculations. Fits to 1751 known binding
energies for N,Z lead to RMS errors of 614 keV with 14 parameters and
388 keV with 28 parameters. The latter is easily reduced to a 20 parameter form
at 423 keV.Comment: 6 pages, REVTEX dialec
Mirror displacement energies and neutron skins
A gross estimate of the neutron skin [0.80(5) fm] is extracted from
experimental proton radii, represented by a four parameter fit, and observed
mirror displacement energies (CDE). The calculation of the latter relies on an
accurately derived Coulomb energy and smooth averages of the charge symmetry
breaking potentials constrained to state of the art values. The only free
parameter is the neutron skin itself. The Nolen Schiffer anomaly is reduced to
small deviations (rms=127 keV) that exhibit a secular trend. It is argued that
with state of the art shell model calculations the anomaly should disappear.
Highly accurate fits to proton radii emerge as a fringe benefit.Comment: 4 pages 3 figures, superseeds first part of nucl-th/0104048 Present
is new extended version: 5 pages 4 figures. Explains more clearly the
achievements of the previous on
Coulomb displacement energies, energy differenced and neutron skins
A Fock space representation of the monopole part of the Coulomb potential is
presented. Quantum effects show through a small orbital term in . Once
it is averaged out, the classical electrostatic energy emerges as an
essentially exact expression, which makes it possible to eliminate the
Nolen-Schiffer anomaly, and to estimate neutron skins and the evolution of
radii along yrast states of mirror nuclei. The energy differences of the latter
are quantitatively reproduced by the monopole term and a schematic multipole
one.Comment: 4 pages, 3 figures, Revte
L1-determined ideals in group algebras of exponential Lie groups
A locally compact group is said to be -regular if the natural map
\Psi:\Prim C^\ast(G)\to\Prim_{\ast} L^1(G) is a homeomorphism with respect to
the Jacobson topologies on the primitive ideal spaces \Prim C^\ast(G) and
\Prim_{\ast} L^1(G). In 1980 J. Boidol characterized the -regular ones
among all exponential Lie groups by a purely algebraic condition. In this
article we introduce the notion of -determined ideals in order to discuss
the weaker property of primitive -regularity. We give two sufficient
criteria for closed ideals of to be -determined. Herefrom
we deduce a strategy to prove that a given exponential Lie group is primitive
-regular. The author proved in his thesis that all exponential Lie groups
of dimension have this property. So far no counter-example is known.
Here we discuss the example , the only critical one in dimension
Garvey-Kelson Relations for Nuclear Charge Radii
The Garvey-Kelson relations (GKRs) are algebraic expressions originally
developed to predict nuclear masses. In this letter we show that the GKRs
provide a fruitful framework for the prediction of other physical observables
that also display a slowly-varying dynamics. Based on this concept, we extend
the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out
of the approximately 800 nuclei whose charge radius is experimentally known. We
find a rms deviation between the GK predictions and the experimental values of
only 0.01 fm. This should be contrasted against some of the most successful
microscopic models that yield rms deviations almost three times as large.
Predictions - with reliable uncertainties - are provided for 116 nuclei whose
charge radius is presently unknown.Comment: 4 pages and 3 figure
Quantization of Wilson loops in Wess-Zumino-Witten models
We describe a non-perturbative quantization of classical Wilson loops in the
WZW model. The quantized Wilson loop is an operator acting on the Hilbert space
of closed strings and commuting either with the full Kac-Moody chiral algebra
or with one of its subalgebras. We prove that under open/closed string duality,
it is dual to a boundary perturbation of the open string theory. As an
application, we show that such operators are useful tools for identifying fixed
points of the boundary renormalization group flow.Comment: 24 pages. Version published in JHE
Three-body monopole corrections to the realistic interactions
It is shown that a very simple three-body monopole term can solve practically
all the spectroscopic problems--in the , and shells--that were
hitherto assumed to need drastic revisions of the realistic potentials.Comment: 4 pages, 5figure
Happiness on Tap: Piped Water Adoption in Urban Morocco
We study the demand for household water connections in urban Morocco, and the effect of such connections on household welfare. In the northern city of Tangiers, among homeowners without a private connection to the cityâs water grid, a random subset was offered a simplified procedure to purchase a household connection on credit (at a zero percent interest rate). Take-up was high, at 69%. Because all households in our sample had access to the water grid through free public taps (often located fairly close to their homes), household connections did not lead to any improvement in the quality of the water households consumed; and despite significant increase in the quantity of water consumed, we find no change in the incidence of waterborne illnesses. Nevertheless, we find that households are willing to pay a substantial amount of money to have a private tap at home. Being connected generates important time gains, which are used for leisure and social activities, rather than productive activities. Because water is often a source of tension between households, household connections improve social integration and reduce conflict. Overall, within 6 months, self-reported well-being improved substantially among households in the treatment group, despite the financial cost of the connection. Our results suggest that facilitating access to credit for households to finance lump sum quality-of-life investments can significantly increase welfare, even if those investments do not result in income or health gains
Microscopic calculation of proton capture reactions in mass 60-80 region and its astrophysical implications
Microscopic optical potentials obtained by folding the DDM3Y interaction with
the densities from Relativistic Mean Field approach have been utilized to
evaluate S-factors of low-energy reactions in mass 60-80 region
and to compare with experiments. The Lagrangian density FSU Gold has been
employed. Astrophysical rates for important proton capture reactions have been
calculated to study the behaviour of rapid proton nucleosynthesis for waiting
point nuclei with mass less than A=80
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