5 research outputs found
Inflation, bifurcations of nonlinear curvature Lagrangians and dark energy
A possible equivalence of scalar dark matter, the inflaton, and modified
gravity is analyzed. After a conformal mapping, the dependence of the effective
Lagrangian on the curvature is not only singular but also bifurcates into
several almost Einsteinian spaces, distinguished only by a different effective
gravitational strength and cosmological constant. A swallow tail catastrophe in
the bifurcation set indicates the possibility for the coexistence of different
Einsteinian domains in our Universe. This `triple unification' may shed new
light on the nature and large scale distribution not only of dark matter but
also on `dark energy', regarded as an effective cosmological constant, and
inflation.Comment: 20 pages, 8 figures, Proceedings of the 11th Marcel Grossmann Meeting
(MG11) in Berlin, Germany, July 23-29, 200
Classification of Inflationary Einstein--Scalar--Field--Models via Catastrophe Theory
Various scenarios of the initial inflation of the universe are distinguished
by the choice of a scalar field {\em potential} which simulates a
{\it temporarily} non--vanishing {\em cosmological term}. Our new method, which
involves a reparametrization in terms of the Hubble expansion parameter ,
provides a classification of allowed inflationary potentials and of the
stability of the critical points. It is broad enough to embody all known {\it
exact} solutions involving one scalar field as special cases. Inflation
corresponds to the evolution of critical points of some catastrophe manifold.
The coalescence of its nondegenerate critical points with the creation of a
degenerate critical point corresponds the reheating phase of the universe. This
is illustrated by several examples.Comment: 12 pages, REVTeX, no figure
Gravitational stability of boson stars
We investigate the stability of general-relativistic boson stars by classifying singularities of differential mappings and compare it with the results of perturbation theory. Depending on the particle number, the star has the following regimes of behavior: stable, metastable, pulsation, and collapse