1,998,621 research outputs found
Analytical results for a Bessel function times Legendre polynomials class integrals
When treating problems of vector diffraction in electromagnetic theory, the
evaluation of the integral involving Bessel and associated Legendre functions
is necessary. Here we present the analytical result for this integral that will
make unnecessary numerical quadrature techniques or localized approximations.
The solution is presented using the properties of the Bessel and associated
Legendre functions.Comment: 4 page
The origin of blue-shifted absorption features in the X-ray spectrum of PG 1211+143: Outflow or disc?
In some radio-quiet active galaxies (AGN), high-energy absorption features in
the x-ray spectra have been interpreted as Ultrafast Outflows (UFOs) -- highly
ionised material (e.g. Fe XXV and Fe XXVI) ejected at mildly relativistic
velocities. In some cases, these outflows can carry energy in excess of the
binding energy of the host galaxy. Needless to say, these features demand our
attention as they are strong signatures of AGN feedback and will influence
galaxy evolution. For the same reason, alternative models need to be discussed
and refuted or confirmed. Gallo & Fabian proposed that some of these features
could arise from resonance absorption of the reflected spectrum in a layer of
ionised material located above and corotating with the accretion disc.
Therefore, the absorbing medium would be subjected to similar blurring effects
as seen in the disc. A priori, the existence of such plasma above the disc is
as plausible as a fast wind. In this work, we highlight the ambiguity by
demonstrating that the absorption model can describe the ~7.6 keV absorption
feature (and possibly other features) in the quasar PG 1211+143, an AGN that is
often described as a classic example of an UFO. In this model, the 2-10 keV
spectrum would be largely reflection dominated (as opposed to power law
dominated in the wind models) and the resonance absorption would be originating
in a layer between about 6 and 60 gravitational radii. The studies of such
features constitutes a cornerstone for future X-ray observatories like Astro-H
and Athena+. Should our model prove correct, or at least important in some
cases, then absorption will provide another diagnostic tool with which to probe
the inner accretion flow with future missions.Comment: 4 pages. Accepted for publication in MNRAS Letter
Solving the strong CP problem with non-conventional CP
A very simple model is presented where all CP violation in Nature is
spontaneous in origin. The CKM phase is generated unsuppressed and the strong
CP problem is solved with only moderately small couplings between the SM and
the CP violation sector or mediator sector because corrections to
arise only at two loops. The latter feature follows from an
underlying unconventional CP symmetry of order 4 imposed in the sectors beyond
the SM composed of only two vector-like quarks of charge and one complex
scalar singlet. No additional symmetry is necessary to implement the
Nelson-Barr mechanism.Comment: Comments added, comply with published versio
Fire extinguishant materials
Fire extinguishant composition comprising a mixture of a finely divided aluminum compound and alkali metal, stannous or plumbous halide is provided. Aluminum compound may be aluminum hydroxide, alumina or boehmite but preferably it is an alkali metal dawsonite. The metal halide may be an alkali metal, e.g. potassium iodide, bromide or chloride or stannous or plumbous iodide, bromide or chloride. Potassium iodide is preferred
The electron screening puzzle and nuclear clustering
Accurate measurements of nuclear reactions of astrophysical interest within,
or close to, the Gamow peak, show evidence of an unexpected effect attributed
to the presence of atomic electrons in the target. The experiments need to
include an effective "screening" potential to explain the enhancement of the
cross sections at the lowest measurable energies. Despite various theoretical
studies conducted over the past 20 years and numerous experimental
measurements, a theory has not yet been found that can explain the cause of the
exceedingly high values of the screening potential needed to explain the data.
In this letter we show that instead of an atomic physics solution of the
"electron screening puzzle", the reason for the large screening potential
values is in fact due to clusterization effects in nuclear reactions, in
particular for reaction involving light nuclei.Comment: 6 pages, 2 figures, accepted for publication in Physics Letters
Studies of noise transmission in advanced composite material structures
Noise characteristics of advanced composite material fuselages were discussed from the standpoints of applicable research programs and noise transmission theory. Experimental verification of the theory was also included
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