1,186 research outputs found
Evaluation of Effective Astrophysical S factor for Non-Resonant Reactions
We derived analytic formulas of the effective S astrophysical S factor,S^eff
for a non-resonant reaction of charged particles using a Taylor expension of
the astrophysical S factor and a uniform approximation.The formulas will be
able to generate generate more accurate approximation to S^eff than previous
ones
Symmetry Breaking Study with Deformed Ensembles
A random matrix model to describe the coupling of m-fold symmetry in
constructed. The particular threefold case is used to analyze data on
eigenfrequencies of elastomechanical vibration of an anisotropic quartz block.
It is suggested that such experimental/theoretical study may supply powerful
means to discern intrinsic symmetries in physical systems.Comment: 12 pages, 5 figure
Sparrows can't sing : East End kith and kinship in the 1960s
Sparrows Canât Sing (1963) was the only feature film directed by
the late and much lamented Joan Littlewood. Set and filmed in
the East End, where she worked for many years, the film deserves
more attention than it has hitherto received. Littlewoodâs career
spanned documentary (radio recordings made with Ewan MacColl
in the North of England in the 1930s) to directing for the stage
and the running of the Theatre Royal in Londonâs Stratford East,
often selecting material which aroused memories in local audiences
(Leach 2006: 142). Many of the actors trained in her Theatre
Workshop subsequently became better known for their appearances
on film and television. Littlewood herself directed hardly any material
for the screen: Sparrows Canât Sing and a 1964 series of television
commercials for the British Egg Marketing Board, starring Theatre
Workshopâs Avis Bunnage, were rare excursions into an area of practice
which she found constraining and unamenable (Gable 1980: 32).
The hybridity and singularity of Littlewoodâs feature may answer,
in some degree, for its subsequent neglect. However, Sparrows Canât
Sing makes a significant contribution to a group of films made in
Britain in the 1960s which comment generally on changes in the
urban and social fabric. It is especially worthy of consideration,
I shall argue, for the use which Littlewood made of a particular
communityâs attitudes â sentimental and critical â to such changes and
for its amalgamation of an attachment to documentary techniques
(recording an aural landscape on location) with a preference for nonnaturalistic
delivery in performance
Level density for deformations of the Gaussian orthogonal ensemble
Formulas are derived for the average level density of deformed, or
transition, Gaussian orthogonal random matrix ensembles. After some general
considerations about Gaussian ensembles we derive formulas for the average
level density for (i) the transition from the Gaussian orthogonal ensemble
(GOE) to the Poisson ensemble and (ii) the transition from the GOE to GOEs.Comment: 7 pages revtex4, 5 eps figures, submitted to Phys. Rev.
Addendum: Attenuation of the intensity within a superdeformed band
We investigate a random matrix model [Phys. Rev. C {\bf 65} 024302 (2002] for
the decay-out of a superdeformed band as a function of the parameters:
, , and . Here
is the spreading width for the mixing of an SD state
with a normally deformed (ND) doorway state , and
are the electromagnetic widths of the the SD and ND states respectively, is
the mean level spacing of the compound ND states and is the energy
difference between and . The maximum possible effect of an
order-chaos transition is inferred from analytical and numerical calculations
of the decay intensity in the limiting cases for which the ND states obey
Poisson and GOE statistics. Our results show that the sharp attenuation of the
decay intensity cannot be explained solely by an order-chaos transition.Comment: 4 pages, 4 figures, submitted to Physical Review
Energy averages over regular and chaotic states in the decay out of superdeformed bands
We describe the decay out of a superdeformed band using the methods of
reaction theory. Assuming that decay-out occurs due to equal coupling (on
average) to a sea of equivalent chaotic normally deformed (ND) states, we
calculate the average intraband decay intensity and show that it can be written
as an ``optical'' background term plus a fluctuation term, in total analogy
with average nuclear cross sections. We also calculate the variance in closed
form. We investigate how these objects are modified when the decay to the ND
states occurs via an ND doorway and the ND states' statistical properties are
changed from chaotic to regular. We show that the average decay intensity
depends on two dimensionless variables in the first case while in the second
case, four variables enter the picture.Comment: 8 pages, 1 figure, presented at FUSION03, Matsushima, Miyagi, Japan,
Nov 12-15, 2003, to appear in Progress of Theoretical Physics; corrected
typo
Symmetry Breaking Study with Random Matrix Ensembles
A random matrix model to describe the coupling of -fold symmetry is
constructed. The particular threefold case is used to analyze data on
eigenfrequencies of elastomechanical vibration of an anisotropic quartz block.
It is suggested that such experimental/theoretical study may supply a powerful
means to discern intrinsic symmetry of physical systems.Comment: 12 pages, 3 figures Contribution to the International Workshop on
Nuclei and Mesoscopic Physics (WNM07), 20-22 October, Michigan Sate
University, East Lansing, Michigan. To appear in a AIP Proceeding (Pawel
Danielewicz, Editor
PERFORMANCE OF THE EXACT AND CHI-SQUARE TESTS ON SPARSE CONTINGENCY TABLES
A cross-sectional observational study design was used to determine the prevalence of Escherichia coli 0157:H7 in wild deer feces. Samples were voluntarily submitted at a number of different locations. In order to determine if the proportions of E. coli 0157: H7 positive samples submitted were equal for each of the 26 locations, a 26 by 2 contingency table was analyzed. There were only four E. coli 0157:H7 positive samples, which resulted in a sparse table. It is possible to obtain statistically significant results in sparse tables using Fisher\u27s exact test, whereas the chi-square test is generally unreliable in such situations. Thus, Fisher\u27s exact test should be considered when small expected cell counts bring into question the validity of the chi-square test. However, the statistical conclusions based on either the exact test or an asymptotic chi-square test are shown to vary drastically by slight alterations in the distribution of non-empty cells. Therefore, a different statistical conclusion very easily could have been reached if a volunteer had submitted a sample at a different location. In addition, we show that the computational times for exact tests in SASÂź can be an applicational limitation
How large is the spreading width of a superdeformed band?
Recent models of the decay out of superdeformed bands can broadly be divided
into two categories. One approach is based on the similarity between the
tunneling process involved in the decay and that involved in the fusion of
heavy ions, and builds on the formalism of nuclear reaction theory. The other
arises from an analogy between the superdeformed decay and transport between
coupled quantum dots. These models suggest conflicting values for the spreading
width of the decaying superdeformed states. In this paper, the decay of
superdeformed bands in the five even-even nuclei in which the SD excitation
energies have been determined experimentally is considered in the framework of
both approaches, and the significance of the difference in the resulting
spreading widths is considered. The results of the two models are also compared
to tunneling widths estimated from previous barrier height predictions and a
parabolic approximation to the barrier shape
- âŠ