7 research outputs found
A Wasserstein approach to the one-dimensional sticky particle system
We present a simple approach to study the one-dimensional pressureless Euler
system via adhesion dynamics in the Wasserstein space of probability measures
with finite quadratic moments.
Starting from a discrete system of a finite number of "sticky" particles, we
obtain new explicit estimates of the solution in terms of the initial mass and
momentum and we are able to construct an evolution semigroup in a
measure-theoretic phase space, allowing mass distributions with finite
quadratic moment and corresponding L^2-velocity fields. We investigate various
interesting properties of this semigroup, in particular its link with the
gradient flow of the (opposite) squared Wasserstein distance.
Our arguments rely on an equivalent formulation of the evolution as a
gradient flow in the convex cone of nondecreasing functions in the Hilbert
space L^2(0,1), which corresponds to the Lagrangian system of coordinates given
by the canonical monotone rearrangement of the measures.Comment: Added reference
Dynamics of a thin shell in the Reissner-Nordstrom metric
We describe the dynamics of a thin spherically symmetric gravitating shell in
the Reissner-Nordstrom metric of the electrically charged black hole. The
energy-momentum tensor of electrically neutral shell is modelled by the perfect
fluid with a polytropic equation of state. The motion of a shell is described
fully analytically in the particular case of the dust equation of state. We
construct the Carter-Penrose diagrams for the global geometry of the eternal
black hole, which illustrate all possible types of solutions for moving shell.
It is shown that for some specific range of initial parameters there are
possible the stable oscillating motion of the shell transferring it
consecutively in infinite series of internal universes. We demonstrate also
that this oscillating type of motion is possible for an arbitrary polytropic
equation of state on the shell.Comment: 17 pages, 7 figure