108 research outputs found
The Unseen Hole
Every story in this collection is an escape attempt. Some have better tools and plans than others, but they\u27re all working towards a shared goal. When I sit down to write, I often picture the small crevices in my brain the ideas squeeze through before dropping down into the sewer of my imagination. If they manage to break free, then I clean them off, picking away bits of filth, until they\u27re able to stand and grow on their own.
The characters filling my thesis are composite sketches of people I’ve known, animals I’ve met, and a sampling of my insecurities and deepest, darkest fears. It’s important that these characters exist because their presence on the page means one less worry in my head. The bleach drinking teenagers, rapidly expanding men, amateur executioners, and Borscht Belt comedians who fill these pages are me, and I am them
Design, Synthesis, and Screening of Non-Estrogenic Bisphenol A mimics
Undergraduate
Basi
Stability of Transparent Spherically Symmetric Thin Shells and Wormholes
The stability of transparent spherically symmetric thin shells (and
wormholes) to linearized spherically symmetric perturbations about static
equilibrium is examined. This work generalizes and systematizes previous
studies and explores the consequences of including the cosmological constant.
The approach shows how the existence (or not) of a domain wall dominates the
landscape of possible equilibrium configurations.Comment: 12 pages, 7 figures, revtex. Final form to appear in Phys. Rev.
Gravitationally Collapsing Shells in (2+1) Dimensions
We study gravitationally collapsing models of pressureless dust, fluids with
pressure, and the generalized Chaplygin gas (GCG) shell in (2+1)-dimensional
spacetimes. Various collapse scenarios are investigated under a variety of the
background configurations such as anti-de Sitter(AdS) black hole, de Sitter
(dS) space, flat and AdS space with a conical deficit. As with the case of a
disk of dust, we find that the collapse of a dust shell coincides with the
Oppenheimer-Snyder type collapse to a black hole provided the initial density
is sufficiently large. We also find -- for all types of shell -- that collapse
to a naked singularity is possible under a broad variety of initial conditions.
For shells with pressure this singularity can occur for a finite radius of the
shell. We also find that GCG shells exhibit diverse collapse scenarios, which
can be easily demonstrated by an effective potential analysis.Comment: 27 pages, Latex, 11 figures, typos corrected, references added, minor
amendments in introduction and conclusion introd
Expanding and Collapsing Scalar Field Thin Shell
This paper deals with the dynamics of scalar field thin shell in the
Reissner-Nordstrm geometry. The Israel junction conditions between
Reissner-Nordstrm spacetimes are derived, which lead to the equation
of motion of scalar field shell and Klien-Gordon equation. These equations are
solved numerically by taking scalar field model with the quadratic scalar
potential. It is found that solution represents the expanding and collapsing
scalar field shell. For the better understanding of this problem, we
investigate the case of massless scalar field (by taking the scalar field
potential zero). Also, we evaluate the scalar field potential when is an
explicit function of . We conclude that both massless as well as massive
scalar field shell can expand to infinity at constant rate or collapse to zero
size forming a curvature singularity or bounce under suitable conditions.Comment: 15 pages, 11 figure
Scalar hairy black holes and solitons in asymptotically flat spacetimes
A numerical analysis shows that a class of scalar-tensor theories of gravity
with a scalar field minimally and nonminimally coupled to the curvature allows
static and spherically symmetric black hole solutions with scalar-field hair in
asymptotically flat spacetimes. In the limit when the horizon radius of the
black hole tends to zero, regular scalar solitons are found. The asymptotically
flat solutions are obtained provided that the scalar potential of the
theory is not positive semidefinite and such that its local minimum is also a
zero of the potential, the scalar field settling asymptotically at that
minimum. The configurations for the minimal coupling case, although unstable
under spherically symmetric linear perturbations, are regular and thus can
serve as counterexamples to the no-scalar-hair conjecture. For the nonminimal
coupling case, the stability will be analyzed in a forthcoming paper.Comment: 7 pages, 10 postscript figures, file tex, new postscript figs. and
references added, stability analysis revisite
No-scalar hair conjecture in asymptotic de-Sitter spacetime
We discuss the no-hair conjecture in the presence of a cosmological constant.
For the firststep the real scalar field is considered as the matter field and
the spacetime is assumed to be static spherically symmetric. If the scalar
field is massless or has a convex potential such as a mass term, it is proved
that there is no regular black hole solution. For a general positive potential,
we search for black hole solutions which support the scalar field with a double
well potential, and find them by numerical calculations. The existence of such
solutions depends on the values of the vacuum expectation value and the
self-coupling constant of the scalar field. When we take the zero horizon
radius limit, the solution becomes a boson star like solution which we found
before. However new solutions are found to be unstable against the linear
perturbation. As a result we can conclude that the no-scalar hair conjecture
holds in the case of scalar fields with a convex or double well potential.Comment: 9 pages, 2 Postscript figure
A simple theorem to generate exact black hole solutions
Under certain conditions imposed on the energy-momentum tensor, a theorem
that characterizes a two-parameter family of static and spherically symmetric
solutions to Einstein's field equations (black holes), is proved. A discussion
on the asymptotics, regularity, and the energy conditions is provided. Examples
that include the best known exact solutions within these symmetries are
considered. A trivial extension of the theorem includes the cosmological
constant {\it ab-initio}, providing then a three-parameter family of solutions.Comment: 14 pages; RevTex; no figures; typos corrected; references adde
Non-Commutative Correction to Thin Shell Collapse in Reissner Nordstrm Geometry
This paper investigates the polytropic matter shell collapse in the
non-commutative Reissner-Nordstrm geometry. Using the Israel
criteria, equation of motion for the polytropic matter shell is derived. In
order to explore the physical aspects of this equation, the most general
equation of state, , has been used for finite
and infinite values of . The effective potentials corresponding to the
equation of motion have been used to explain different states of the matter
shell collapse. The numerical solution of the equation of motion predicts
collapse as well as expansion depending on the choice of initial data. Further,
in order to include the non-commutative correction, we modify the matter
components and re-formulate the equation of motion as well as the corresponding
effective potentials by including non-commutative factor and charge parameter.
It is concluded that charge reduces the velocity of the expanding or collapsing
matter shell but does not bring the shell to static position. While the
non-commutative factor with generic matter favors the formation of black hole.Comment: 18 pages,17 figure
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