36,032 research outputs found
Spherical Dust Collapse in Higher Dimensions
We consider here the question if it is possible to recover cosmic censorship
when a transition is made to higher dimensional spacetimes, by studying the
spherically symmetric dust collapse in an arbitrary higher spacetime dimension.
It is pointed out that if only black holes are to result as end state of a
continual gravitational collapse, several conditions must be imposed on the
collapsing configuration, some of which may appear to be restrictive, and we
need to study carefully if these can be suitably motivated physically in a
realistic collapse scenario. It would appear that in a generic higher
dimensional dust collapse, both black holes and naked singularities would
develop as end states as indicated by the results here. The mathematical
approach developed here generalizes and unifies the earlier available results
on higher dimensional dust collapse as we point out. Further, the dependence of
black hole or naked singularity end states as collapse outcomes, on the nature
of the initial data from which the collapse develops, is brought out explicitly
and in a transparent manner as we show here. Our method also allows us to
consider here in some detail the genericity and stability aspects related to
the occurrence of naked singularities in gravitational collapse.Comment: Revtex4, Title changed, To appear in Physical Review
Modal couping effects in the free vibration of elastically interconnected beams
The problem of free vibration of a uniform beam elastically interconnected to a cantilevered beam, representing an idealized launch vehicle aeroelastic model in a wind tunnel, is studied. With elementary beam theory modelling, numerical results are obtained for the frequencies, mode shapes and the generalized modal mass of this elastically cou pled13; system, for a range of values of the spring constants and cantilevered beam stiffness and inertia values. The study shows that when the linear springs are supported at the nodal points corresponding to the first free-free beam mode, the modal interaction comes primarily from the rotational spring stiffness. The effect of the linear spring stiffness on the higher model modes is also found to be marginal. However, the rotational stiffness has a significant effect on all the predominantly model modes as it couples the model13; deformations and the support rod deformations. The study also shows that though the variations in the stiffness or the inertia values of the cantilever beam affect only the13; predominantly cantilever modes, these variations become important because of the fact that the cantilevered support rod frequencies may come close to, or even cross over, the13; predominantly model mode frequencies. The results also bring out the fact that shifting of the support points away from the first mode nodal points has a maximum effect only on the first model mode
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