957 research outputs found
Quasi-Two-Body Decays of Nonstrange Baryons
We examine the decays of nonstrange baryons to the final states ,
, , , , , and
, in a relativized pair-creation() model which has
been developed in a previous study of the decays of the same baryon
states. As it is our goal to provide a guide for the possible discovery of new
baryon states at CEBAF and elsewhere, we examine the decays of resonances which
have already been seen in the partial-wave analyses, along with those of states
which are predicted by the quark model but which remain undiscovered. The level
of agreement between our calculation and the available widths from the
partial-wave analyses is encouraging.Comment: 41 pages, CEBAF-TH-93-1
The Electric Dipole Form Factor of the Nucleon in Chiral Perturbation Theory to Sub-leading Order
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD
theta term and from the quark color-electric dipole moments is calculated in
chiral perturbation theory to sub-leading order. This is the lowest order in
which the isoscalar EDFF receives a calculable, non-analytic contribution from
the pion cloud. In the case of the theta term, the expected lower bound on the
deuteron electric dipole moment is |d_d| > 1.4 10^(-4) \theta e fm. The
momentum dependence of the isovector EDFF is proportional to a non-derivative
time-reversal-violating pion-nucleon coupling, and the scale for momentum
variation ---appearing, in particular, in the radius of the form factor--- is
the pion mass.Comment: 14 pages, 3 figure
The imposition of Cauchy data to the Teukolsky equation I: The nonrotating case
Gravitational perturbations about a Kerr black hole in the Newman-Penrose
formalism are concisely described by the Teukolsky equation. New numerical
methods for studying the evolution of such perturbations require not only the
construction of appropriate initial data to describe the collision of two
orbiting black holes, but also to know how such new data must be imposed into
the Teukolsky equation. In this paper we show how Cauchy data can be
incorporated explicitly into the Teukolsky equation for non-rotating black
holes. The Teukolsky function and its first time derivative
can be written in terms of only the 3-geometry and the
extrinsic curvature in a gauge invariant way. Taking a Laplace transform of the
Teukolsky equation incorporates initial data as a source term. We show that for
astrophysical data the straightforward Green function method leads to divergent
integrals that can be regularized like for the case of a source generated by a
particle coming from infinity.Comment: 9 pages, REVTEX. Misprints corrected in formulas (2.4)-(2.7). Final
version to appear in PR
Connecting Numerical Relativity and Data Analysis of Gravitational Wave Detectors
Gravitational waves deliver information in exquisite detail about
astrophysical phenomena, among them the collision of two black holes, a system
completely invisible to the eyes of electromagnetic telescopes. Models that
predict gravitational wave signals from likely sources are crucial for the
success of this endeavor. Modeling binary black hole sources of gravitational
radiation requires solving the Eintein equations of General Relativity using
powerful computer hardware and sophisticated numerical algorithms. This
proceeding presents where we are in understanding ground-based gravitational
waves resulting from the merger of black holes and the implications of these
sources for the advent of gravitational-wave astronomy.Comment: Appeared in the Proceedings of 2014 Sant Cugat Forum on Astrophysics.
Astrophysics and Space Science Proceedings, ed. C.Sopuerta (Berlin:
Springer-Verlag
Nanofabrication by magnetic focusing of supersonic beams
We present a new method for nanoscale atom lithography. We propose the use of
a supersonic atomic beam, which provides an extremely high-brightness and cold
source of fast atoms. The atoms are to be focused onto a substrate using a thin
magnetic film, into which apertures with widths on the order of 100 nm have
been etched. Focused spot sizes near or below 10 nm, with focal lengths on the
order of 10 microns, are predicted. This scheme is applicable both to precision
patterning of surfaces with metastable atomic beams and to direct deposition of
material.Comment: 4 pages, 3 figure
Mirror Symmetry and Other Miracles in Superstring Theory
The dominance of string theory in the research landscape of quantum gravity
physics (despite any direct experimental evidence) can, I think, be justified
in a variety of ways. Here I focus on an argument from mathematical fertility,
broadly similar to Hilary Putnam's 'no miracles argument' that, I argue, many
string theorists in fact espouse. String theory leads to many surprising,
useful, and well-confirmed mathematical 'predictions' - here I focus on mirror
symmetry. These predictions are made on the basis of general physical
principles entering into string theory. The success of the mathematical
predictions are then seen as evidence for framework that generated them. I
attempt to defend this argument, but there are nonetheless some serious
objections to be faced. These objections can only be evaded at a high
(philosophical) price.Comment: For submission to a Foundations of Physics special issue on "Forty
Years Of String Theory: Reflecting On the Foundations" (edited by G. `t
Hooft, E. Verlinde, D. Dieks and S. de Haro)
The Effective Chiral Lagrangian From the Theta Term
We construct the effective chiral Lagrangian involving hadronic and
electromagnetic interactions originating from the QCD theta term. We impose
vacuum alignment at both quark and hadronic levels, including field
redefinitions to eliminate pion tadpoles. We show that leading
time-reversal-violating (TV) hadronic interactions are related to
isospin-violating interactions that can in principle be determined from
charge-symmetry-breaking experiments. We discuss the complications that arise
from TV electromagnetic interactions. Some implications of the expected sizes
of various pion-nucleon TV interactions are presented, and the pion-nucleon
form factor is used as an example.Comment: 57 page
Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances
1. Movements of many animals along a life-path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long-life radio tags.
2. Ex-natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra-natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post-nuptial movement exceeded 2 km.
3. Initiation of early ex-natal dispersal was enhanced by presence of many sibs, but also by lack of worm-rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass-feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass).
4. Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat.
5. Factors that acted most strongly in ½-km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in ½-km buffers, especially during early ex-natal dispersal, suggested that buzzards became primed by these factors to travel far.
6. Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long-term priming or poor habitat beyond the study area
Understanding preventive behaviors among mid-Western African-American men: a pilot qualitative study of prostate screening
http://dx.doi.org/10.1016/j.jomh.2011.03.00
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