40 research outputs found

    Strong lensing as a test for Conformal Weyl Gravity

    Get PDF
    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 γr\gamma r, which can explain the observed galactic rotation curves with a value for γ\gamma given by +1026m1\sim + 10^{-26} \mathrm{m}^{-1}. Previous work has also shown that CWG can explain lensing observations, but with γ1026m1\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 γ\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

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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

    Get PDF
    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

    Full text link
    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