45 research outputs found

### Strong lensing as a test for Conformal Weyl Gravity

Conformal Weyl Gravity (CWG) predicts galactic rotation curves without
invoking dark matter. This makes CWG an interesting candidate theory as an
alternative to GR. This removal of the necessity of dark matter arises because
the exact exterior solution in CWG for a static, spherically symmetric source
provides a linear potential $\gamma r$, which can explain the observed galactic
rotation curves with a value for $\gamma$ given by $\sim + 10^{-26}
\mathrm{m}^{-1}$. Previous work has also shown that CWG can explain lensing
observations, but with $\gamma\sim - 10^{-26} \mathrm{m}^{-1}$ in order to
ensure converging rays of light rather than diverging ones. Even though
different expressions for the angle of deflection have been derived in CWG in
order to remove this inconsistency, this paper shows that the $\gamma$ required
to fit the lensing data is several orders of magnitude higher than that
required to fit the galactic rotation curves.Comment: 6 pages, 2 tables, 2 figure

### The EPR correlation in Kerr-Newman spacetime

The EPR correlation has become an integral part of quantum communications as
has general relativity in classical communication theory, however when combined
an apparent deterioration is observed for spin states. We consider appropriate
changes in directions of measurement to exploit full EPR entanglement for a
pair of particles and show that it can be deduced only up to the outer even
horizon of a Kerr-Newman black hole, even in the case of freely falling
observer.Comment: 8 pages, 3 figure

### Rotating charged cylindrical black holes as particle accelerators

It has recently been pointed out that arbitrary center-of-mass energies may be obtained for particle
collisions near the horizon of an extremal Kerr black hole. We investigate this mechanism in cylindrical
topology. In particular we consider the center-of-mass energies of a cylindrical black hole with an
extremal rotation and charge parameter. The geodesics are first derived with a rotating charged cylindrical
black hole producing the background gravitational field. Finally the center-of-mass is determined for this
background and its extremal limit is taken.peer-reviewe

### Generalized uncertainty principle in f(R) gravity for a charged black hole

Using f(R) gravity in the Palatini formularism, the metric for a charged spherically symmetric black
hole is derived, taking the Ricci scalar curvature to be constant. The generalized uncertainty principle is
then used to calculate the temperature of the resulting black hole; through this the entropy is found
correcting the Bekenstein-Hawking entropy in this case. Using the entropy the tunneling probability and
heat capacity are calculated up to the order of the Planck length, which produces an extra factor that
becomes important as black holes become small, such as in the case of mini-black holes.peer-reviewe

### Charged Cylindrical Black Holes in Conformal Gravity

Considering cylindrical topology we present the static solution for a charged
black hole in conformal gravity. We show that unlike the general relativistic
case there are two different solutions, both including a factor that when set
to zero recovers the familiar static charged black string solution in
Einstein's theory. This factor gives rise to a linear term in the potential
that also features in the neutral case and may have significant ramifications
for particle trajectories.Comment: 8 page

### A Wideband, Four-Element, All-Digital Beamforming System for Dense Aperture Arrays in Radio Astronomy

Densely-packed, all-digital aperture arrays form a key area of technology
development required for the Square Kilometre Array (SKA) radio telescope. The
design of real-time signal processing systems for digital aperture arrays is
currently a central challenge in pathfinder projects worldwide. We describe
interim results of such work; an heirarchical, frequency-domain beamforming
architecture for synthesising a sky beam from the wideband antenna feeds of
digital aperture arrays.Comment: 4 pages, 6 figure