31 research outputs found
The electromagnetic spike solutions
The aim of this paper is to use the existing relation between polarized
electromagnetic Gowdy spacetimes and vacuum Gowdy spacetimes to find explicit
solutions for electromagnetic spikes by a procedure which has been developed by
one of the authors for gravitational spikes. We present new inhomogeneous
solutions which we call the EME and MEM electromagnetic spike solutions.Comment: V3: 13 pages and 4 figures. No change in main result. Title and names
of the solutions changed to make their physical interpretation more clea
The Dynamics of Inhomogeneous Cosmologies
In this thesis we investigate cosmological models more general than the
isotropic and homogeneous Friedmann-Lemaitre models. We focus on cosmologies
with one spatial degree of freedom, whose matter content consists of a perfect
fluid and the cosmological constant. We formulate the Einstein field equations
as a system of quasilinear first order partial differential equations, using
scale-invariant variables.
The primary goal is to study the dynamics in the two asymptotic regimes, i.e.
near the initial singularity and at late times. We highlight the role of
spatially homogeneous dynamics as the background dynamics, and analyze the
inhomogeneous aspect of the dynamics. We perform a variety of numerical
simulations to support our analysis and to explore new phenomena.Comment: PhD thesis, University of Waterloo, September 2004. 205 page
Future asymptotics of tilted Bianchi type II cosmologies
In this paper we study the future asymptotics of spatially homogeneous
Bianchi type II cosmologies with a tilted perfect fluid with a linear equation
of state. By means of Hamiltonian methods we first find a monotone function for
a special tilted case, which subsequently allows us to construct a new set of
monotone functions for the general tilted type II cosmologies. In the context
of a new partially gauge invariant dynamical system, this then leads to a proof
for a theorem that for the first time gives a complete description of the
future asymptotic states of the general tilted Bianchi type II models. The
generality of our arguments suggests how one can produce monotone functions
that are useful for determining the asymptotics of other tilted perfect fluid
cosmologies, as well as for other sources.Comment: 15 page
Spikes in the Mixmaster regime of G_2 cosmologies
We produce numerical evidence that spikes in the Mixmaster regime of G_2
cosmologies are transient and recurring, supporting the conjecture that the
generalized Mixmaster behavior is asymptotically non-local where spikes occur.
Higher order spike transitions are observed to split into separate first order
spike transitions.Comment: Minor corrections. Matches the published versio
Cosmology: a bird's eye view
In this essay we discuss the difference in views of the Universe as seen by
two different observers. While one of the observers follows a geodesic
congruence defined by the geometry of the cosmological model, the other
observer follows the fluid flow lines of a perfect fluid with a linear equation
of state. We point out that the information these observers collect regarding
the state of the Universe can be radically different; while one observes a
non-inflating ever-expanding ever-lasting universe, the other observer can
experience a dynamical behaviour reminiscent to that of quintessence or even
that of a phantom cosmology leading to a 'big rip' singularity within finite
time (but without the need for exotic forms of matter).Comment: 5 pages; received an honorable mention in the Gravity Research
Foundation Essay Competition, 200