298 research outputs found
Addendum to `Gravitational Geons in 1+1 Dimensions'
In a recent paper [arXiv:0807.0611] I found gravitational geons in two
classes of 1+1 dimensional theories of gravity. In this paper I examine these
theories, with the possibility of a cosmological constant, and find strong
field gravitational geons. In the spacetimes in [arXiv:0807.0611] a test
particle that is reflected from the origin suffers a discontinuity in
. The geons found in this paper do not suffer from this problem.Comment: To appear in Classical and Quantum Gravit
On the Dirac field in the Palatini form of 1/R gravity
In recent papers (astro-ph/0306630, gr-qc/0312041) I have argued that the
observed cosmological acceleration can be accounted for by the inclusion of a
1/R term in the gravitational action in the Palatini formalism. Subsequently,
Flanagan (astro-ph/0308111, gr-qc/0403063) argued that this theory is
equivalent to a scalar-tensor theory which produces corrections to the standard
model that are ruled out experimentally.
In this article I examine the Dirac field coupled to 1/R gravity. The Dirac
action contains the connection which was taken to be the Christoffel symbol,
not an independent quantity, in the papers by Flanagan. Since the metric and
connection are taken to be independent in the Palatini approach it is natural
to allow the connection that appears in the Dirac action to be an independent
quantity. This is the approach that is taken in this paper. The resulting
theory is very different and much more complicated than the one discussed in
Flanagan's papers.Comment: 6 pages, LaTe
- …