61 research outputs found
Critical Phenomena Associated with Boson Stars
We present a brief synopsis of related work (gr-qc/0007039), describing a
study of black hole threshold phenomena for a self-gravitating, massive complex
scalar field in spherical symmetry. We construct Type I critical solutions
dynamically by tuning a one-parameter family of initial data consisting of a
boson star and a massless real scalar field, and numerically evolving this
data. The resulting critical solutions appear to correspond to boson stars on
the unstable branch, as we show via comparisons between our simulations and
perturbation theory. For low-mass critical solutions, we find small ``halos''
of matter in the tails of the solutions, and these distort the profiles which
otherwise agree with unstable boson stars. These halos seem to be artifacts of
the collisions between the original boson stars and the massless fields, and do
not appear to belong to the true critical solutions. From this study, it
appears that unstable boson stars are unstable to dispersal (``explosion'') in
addition to black hole formation. Given the similarities in macroscopic
stability between boson stars and neutron stars, we suggest that similar
phenomena could occur in models of neutron stars.Comment: 6 Pages, 5 Figures, LaTeX. To appear in Proceedings of the 20th Texas
Symposium on Relativistic Astrophysics (Dec 9-15, 2000
Nonminimally coupled topological-defect boson stars: Static solutions
We consider spherically symmetric static composite structures consisting of a
boson star and a global monopole, minimally or non-minimally coupled to the
general relativistic gravitational field. In the non-minimally coupled case,
Marunovic and Murkovic have shown that these objects, so-called boson D-stars,
can be sufficiently gravitationally compact so as to potentially mimic black
holes. Here, we present the results of an extensive numerical parameter space
survey which reveals additional new and unexpected phenomenology in the model.
In particular, focusing on families of boson D-stars which are parameterized by
the central amplitude of the boson field, we find configurations for both the
minimally and non-minimally coupled cases that contain one or more shells of
bosonic matter located far from the origin. In parameter space, each shell
spontaneously appears as one tunes through some critical central amplitude of
the boson field. In some cases the shells apparently materialize at spatial
infinity: in these instances their areal radii are observed to obey a universal
scaling law in the vicinity of the critical amplitude. We derive this law from
the equations of motion and the asymptotic behavior of the fields.Comment: 17 pages, 24 figure
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