413 research outputs found
Static, Self-Gravitating Elastic Bodies
There is proved an existence theorem, in the Newtonian theory, for static,
self-gravitating bodies composed of elastic material. The theorem covers the
case where these bodies are small, but allows them to have arbitrary shape.Comment: 8 page
Bowen-York Tensors
There is derived, for a conformally flat three-space, a family of linear
second-order partial differential operators which send vectors into tracefree,
symmetric two-tensors. These maps, which are parametrized by conformal Killing
vectors on the three-space, are such that the divergence of the resulting
tensor field depends only on the divergence of the original vector field. In
particular these maps send source-free electric fields into TT-tensors.
Moreover, if the original vector field is the Coulomb field on
, the resulting tensor fields on
are nothing but the family of
TT-tensors originally written down by Bowen and York.Comment: 12 pages, Contribution to CQG Special Issue "A Spacetime Safari:
Essays in Honour of Vincent Moncrief
Elastic deformations of compact stars
We prove existence of solutions for an elastic body interacting with itself
through its Newtonian gravitational field. Our construction works for
configurations near one given by a self-gravitating ball of perfect fluid. We
use an implicit function argument. In so doing we have to revisit some
classical work in the astrophysical literature concerning linear stability of
perfect fluid stars. The results presented here extend previous work by the
authors, which was restricted to the astrophysically insignificant situation of
configurations near one of vanishing stress. In particular, "mountains on
neutron stars", which are made possible by the presence of an elastic crust in
neutron stars, can be treated using the techniques developed here.Comment: 29 page
Celestial mechanics of elastic bodies
We construct time independent configurations of two gravitating elastic
bodies. These configurations either correspond to the two bodies moving in a
circular orbit around their center of mass or strictly static configurations.Comment: 16 pages, 2 figures, several typos removed, erratum appeared in
MathZ.263:233,200
Helically symmetric N-particle solutions in scalar gravity
Within a scalar model theory of gravity, where the interaction between
particles is given by the half-retarded + half-advanced solution of the scalar
wave equation, we consider an N-body problem: we investigate configurations of
N particles which form an equilateral N-angle and are in helical motion about
their common center. We prove that there exists a unique equilibrium
configuration and compute the equilibrium radius explicitly in a post-Newtonian
expansion.Comment: 5 pages, 1 figure; minor corrections and changes; accepted for
publication in Physical Review Letter
Existence and uniqueness of Bowen-York Trumpets
We prove the existence of initial data sets which possess an asymptotically
flat and an asymptotically cylindrical end. Such geometries are known as
trumpets in the community of numerical relativists.Comment: This corresponds to the published version in Class. Quantum Grav. 28
(2011) 24500
Helical Solutions in Scalar Gravity
We construct solutions, for small values of and angular frequency
, of special relativistic scalar gravity coupled to ideally elastic
matter which have helical but no stationary or axial symmetry. They correspond
to a body without any symmetries in steady rotation around one of its axes of
inertia, or two bodies moving on a circle around their center of gravity. Our
construction is rigorous, but modulo an unproved conjecture on the
differentiability of a certain functional.Comment: 11 page
Variation of D-region nitric-oxide density with solar activity and season at the dip equator
To study the solar control on electron density (N sub e) in the equatorial D region, a program was initiated with Soviet collaboration in 1979. A total of 31 rockets were launched during the high solar activity period, and 47 rockets during the low solar activity period, from Thumba to measure the N sub e profiles. Analysis of the data shows that the average values of N sub e for the high solar activity period are higher by a factor of about 2 to 3 compared to the low solar activity values. It was found that a single nitric oxide density, (NO), profile cannot reproduce all the observed N sub e profiles. An attempt was made to reproduce theoretically the observed N sub e profiles by introducing variation in (NO) for the different solar activity periods and seasons
Behavior of boundary layer ozone and its precursors over a great alluvial plain of the world: Indo-Gangetic plains
We investigate the special behavior in the distribution of boundary layer ozone and its precursors over world's most extensive tract of uninterrupted alluvium and intensively farmed zones situated in the foothills of Himalayas as major river basin, known as Indo-Gangetic Plains (IGP). The study makes use of a Chemistry-Transport Model forced with dynamical fields and new emission inventories of pollutants established for 2001. It is found that the IGP region is highly vulnerable to human induced pollutant emissions due to conducive synoptic weather pattern which make it a source regions of ozone precursors within which these tracers remain confined and reinforce photochemical production of ozone. In addition, the continental tropical convergence zone and long range transport play a vital role. As a result, elevated levels of ozone concentration (maximum up to 80 ppbv) and its precursors with cellular structure of spatial variation with large seasonality are noticed
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