21,359 research outputs found
Probing the gravitational geon
The Brill-Hartle gravitational geon construct as a spherical shell of small
amplitude, high frequency gravitational waves is reviewed and critically
analyzed. The Regge-Wheeler formalism is used to represent gravitational wave
perturbations of the spherical background as a superposition of tensor
spherical harmonics and an attempt is made to build a non-singular solution to
meet the requirements of a gravitational geon. High-frequency waves are seen to
be a necessary condition for the geon and the field equations are decomposed
accordingly. It is shown that this leads to the impossibility of forming a
spherical gravitational geon. The attempted constructs of gravitational and
electromagnetic geons are contrasted. The spherical shell in the proposed
Brill-Hartle geon does not meet the regularity conditions required for a
non-singular source and hence cannot be regarded as an adequate geon construct.
Since it is the high frequency attribute which is the essential cause of the
geon non-viability, it is argued that a geon with less symmetry is an unlikely
prospect. The broader implications of the result are discussed with particular
reference to the problem of gravitational energy.Comment: Replaced with revised version (substantial changes and additions,
conclusions unchanged), 36 pages, LaTex, 3 figures available from the author
Evaluation of anomalies observed on film from S-190A flight system calibration test
Due to a persistent problem of scratched film from testing of the Skylab S-190A system, a series of tests were designed to identify the cause of the film scratching. The procedures followed in this test for pretest handling and packaging of the film, the makeup of the rolls for processing, and the results of the processed film evaluation are reported
Initial bound state studies in light-front QCD
We present the first numerical QCD bound state calculation based on a
renormalization group-improved light-front Hamiltonian formalism. The QCD
Hamiltonian is determined to second order in the coupling, and it includes
two-body confining interactions. We make a momentum expansion, obtaining an
equal-time-like Schrodinger equation. This is solved for quark-antiquark
constituent states, and we obtain a set of self-consistent parameters by
fitting B meson spectra.Comment: 38 pages, latex, 5 latex figures include
Kleinian Geometry and the N=2 Superstring
This paper is devoted to the exploration of some of the geometrical issues
raised by the superstring. We begin by reviewing the reasons that
-functions for the superstring require it to live in a
four-dimensional self-dual spacetime of signature , together with some
of the arguments as to why the only degree of freedom in the theory is that
described by the gravitational field. We then move on to describe at length the
geometry of flat space, and how a real version of twistor theory is relevant to
it. We then describe some of the more complicated spacetimes that satisfy the
-function equations. Finally we speculate on the deeper significance of
some of these spacetimes.Comment: 30 pages, AMS-Te
On the Size of Hadrons
The form factor and the mean-square radius of the pion are calculated
analytically from a parametrized form of a wave function. The
numerical wave function was obtained previously by solving numerically an
eigenvalue equation for the pion in a particular model. The analytical formulas
are of more general interest than just be valid for the pion and can be
generalized to the case with unequal quark masses. Two different
parametrizations are investigated. Because of the highly relativistic problem,
noticable deviations from a non-relativistic formula are obtained.Comment: 14 pages, minor typos corrected, several points clarified, results
unchange
Faddeev eigenfunctions for two-dimensional Schrodinger operators via the Moutard transformation
We demonstrate how the Moutard transformation of two-dimensional Schrodinger
operators acts on the Faddeev eigenfunctions on the zero energy level and
present some explicitly computed examples of such eigenfunctions for smooth
fast decaying potentials of operators with non-trivial kernel and for deformed
potentials which correspond to blowing up solutions of the Novikov-Veselov
equation.Comment: 11 pages, final remarks are adde
Frost injury to cereals in W.A
Late spring frosts commonly reduce yields and affect the quality of grain in wheat crops, especially in the southern, eastern and north-eastern districts. The damage is usually localised on individual farms, but is sometimes widespread.
Barley, and oats to a lesser extent, are also affected. Average losses of wheat in Western Australia have been estimated at 3 to 5 per cent, per year, or about 2 million bushels on current production figures
Constraining the fundamental parameters of the O-type binary CPD-41degr7733
Using a set of high-resolution spectra, we studied the physical and orbital
properties of the O-type binary CPD-41 7733, located in the core of \ngc. We
report the unambiguous detection of the secondary spectral signature and we
derive the first SB2 orbital solution of the system. The period is 5.6815 +/-
0.0015 d and the orbit has no significant eccentricity. CPD-41 7733 probably
consists of stars of spectral types O8.5 and B3. As for other objects in the
cluster, we observe discrepant luminosity classifications while using
spectroscopic or brightness criteria. Still, the present analysis suggests that
both components display physical parameters close to those of typical O8.5 and
B3 dwarfs. We also analyze the X-ray light curves and spectra obtained during
six 30 ks XMM-Newton pointings spread over the 5.7 d period. We find no
significant variability between the different pointings, nor within the
individual observations. The CPD-41 7733 X-ray spectrum is well reproduced by a
three-temperature thermal mekal model with temperatures of 0.3, 0.8 and 2.4
keV. No X-ray overluminosity, resulting e.g. from a possible wind interaction,
is observed. The emission of CPD-41 7733 is thus very representative of typical
O-type star X-ray emission.Comment: Accepted by ApJ, 15 pages, 9 figure
- …