27,814 research outputs found
Perturbations of critical values in nonsmooth critical point theory
* Supported by Ministero dell’Università e della Ricerca Scientifica e Tecnologica (40% – 1993).
** Supported by Ministero dell’Università e della Ricerca Scientifica e Tecnologica (40% – 1993).The perturbation of critical values for continuous functionals is studied.
An application to eigenvalue problems for variational inequalities is provided
Lagrangian systems with Lipschitz obstacle on manifolds
Lagrangian systems constrained on the closure of an open subset
with Lipschitz boundary in a manifold are considered. Under
suitable assumptions, the existence of infinitely many periodic
solutions is proved
Rest Frame System for Asymptotically Flat Spacetimes
The notion of center of mass for an isolated system has been previously
encoded in the definition of the so called nice sections. In this article we
present a generalization of the proof of existence of solutions to the
linearized equation for nice sections, and formalize a local existence proof of
nice sections relaxing the radiation condition. We report on the differentiable
and non-self-crossing properties of this family of solutions. We also give a
proof of the global existence of nice sections.Comment: 26 pages, LaTeX2
Black hole formation from massive scalar field collapse in the Einstein-de Sitter universe
We study the spherically symmetric collapse of a real, minimally coupled,
massive scalar field in an asymptotically Einstein-de Sitter spacetime
background. By means of an eikonal approximation for the field and metric
functions, we obtain a simple analytical criterion---involving the physical
size and mass scales (the field's inverse Compton wavelength and the spacetime
gravitational mass) of the initial matter configuration---for generic
(non-time-symmetric) initial data to collapse to a black hole. This analytical
condition can then be used to place constraints on the initial primordial black
hole spectrum, by considering spherical density perturbations that re-entered
the horizon during an early matter-dominated phase that immediately followed
inflation.Comment: 9 pages, RevTeX, 3 eps figures; to appear in Phys. Rev.
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