30 research outputs found
The Day the Universes Interacted: Quantum Cosmology without a Wave function
In this article we present a new outlook on the cosmology, based on the
quantum model proposed by M. Hall, D.-A. Deckert and H. Wiseman (HDW). In
continuation of the idea of that model we consider finitely many classical
homogeneous and isotropic universes whose evolutions are determined by the
standard Einstein-Friedman equations but that also interact with each other
quantum-mechanically via the mechanism proposed by HDW. The crux of the idea
lies in the fact that unlike every other interpretation of the quantum
mechanics, the HDW model requires no decoherence mechanism and thus allows the
quantum mechanical effects to manifest themselves not just on micro-scale, but
on a cosmological scale as well. We further demonstrate that the addition of
this new quantum-mechanical interaction lead to a number of interesting
cosmological predictions, and might even provide natural physical explanations
for the phenomena of ``dark matter'' and ``phantom fields''.Comment: 15 pages, RevTeX, 3 figure
The Cosmological Models with Jump Discontinuities
The article is dedicated to one of the most undeservedly overlooked
properties of the cosmological models: the behaviour at, near and due to a jump
discontinuity. It is most interesting that while the usual considerations of
the cosmological dynamics deals heavily in the singularities produced by the
discontinuities of the second kind (a.k.a. the essential discontinuities) of
one (or more) of the physical parameters, almost no research exists to date
that would turn to their natural extension/counterpart: the singularities
induced by the discontinuities of the first kind (a.k.a. the jump
discontinuities). It is this oversight that this article aims to amend. In
fact, it demonstrates that the inclusion of such singularities allows one to
produce a number of very interesting scenarios of cosmological evolution. For
example, it produces the cosmological models with a finite value of the
equation of state parameter even when both the energy density and
the pressure diverge, while at the same time keeping the scale factor finite.
Such a dynamics is shown to be possible only when the scale factor experiences
a finite jump at some moment of time. Furthermore, if it is the first
derivative of the scale factor that experiences a jump, then a whole new and
different type of a sudden future singularity appears. Finally, jump
discontinuities suffered by either a second or third derivatives of a scale
factor lead to cosmological models experiencing a sudden dephantomization -- or
avoiding the phantomization altogether. This implies that theoretically there
should not be any obstacles for extending the cosmological evolution beyond the
corresponding singularities; therefore, such singularities can be considered a
sort of a cosmological phase transition.Comment: 27 pages, 5 figures. Inserted additional references; provided in
Introduction a specific example of a well-known physical field leading to a
cosmological jump discontinuity; seriously expanded the discussion of
possible physical reasons leading to the jump discontinuities in view of
recent theoretical and experimental discoverie
Phantom Cosmology without Big Rip Singularity
We construct phantom energy models with the equation-of-state parameter
such that , but finite-time future singularity does not occur. Such
models can be divided into two classes: (i) energy density increases with time
("phantom energy" without "Big Rip" singularity) and (ii) energy density tends
to constant value with time ("cosmological constant" with asymptotically de
Sitter evolution). The disintegration of bound structure is confirmed in Little
Rip cosmology. Surprisingly, we find that such disintegration (on example of
Sun-Earth system) may occur even in asymptotically de Sitter phantom universe
consistent with observational data. We also demonstrate that non-singular
phantom models admit wormhole solutions as well as possibility of big trip via
wormholes.Comment: LaTeX 13 pages, to appear in PL