111 research outputs found
Determining the Topology and Deflection Angle of Ringholes via Gauss-Bonnet Theorem
In this letter, we use a recent wormhole solution known as a ringhole
[Gonzalez-Diaz, Phys.\ Rev.\ D {\bf 54}, 6122, 1996] to determine the surface
topology and the deflection angle of light in the weak limit approximation
using the Gauss-Bonnet theorem (GBT). We apply the GBT and show that the
surface topology at the wormhole throat is indeed a torus by computing the
Euler characteristic number. As a special case of the ringhole solution, one
can find the Ellis wormhole which has the surface topology of a 2-sphere at the
wormhole throat. The most interesting results of this paper concerns the
problem of gravitational deflection of light in the spacetime of a ringhole
geometry by applying the GBT to the optical ringhole geometry. It is shown
that, the deflection angle of light depends entirely on the geometric structure
of the ringhole geometry encoded by the parameters and , being the
ringhole throat radius and the radius of the circumference generated by the
circular axis of the torus, respectively. As special cases of our general
result, the deflection angle by Ellis wormhole is obtained. Finally, we work
out the problem of deflection of relativistic massive particles and show that
the deflection angle remains unaltered by the speed of the particles.Comment: 7 pages, two-column, 1 figur
Light Deflection with Torsion Effects Caused by a Spinning Cosmic String
Using a new geometrical method introduced by Werner, we find the deflection
angle in the weak limit approximation by a spinning cosmic string in the
context of the Einstein-Cartan (EC) theory of gravity. We begin by adopting the
String-Randers optical metric, then we apply the Gauss-Bonnet theorem to the
optical geometry and derive the leading terms of the deflection angle in the
equatorial plane. Calculations shows that light deflection is affected by the
intrinsic spin of the cosmic string and torsion.Comment: 7 pages, accepted for publication in European Physical Journal
Quantum Tunneling of Spin-1 Particles from a 5D Einstein-Yang-Mills-Gauss-Bonnet Black Hole Beyond Semiclassical Approximation
In the present paper we study the Hawking radiation as a quantum tunneling
effect of spin- particles from a five-dimensional, spherically symmetric,
Einstein-Yang-Mills-Gauss-Bonnet (5D EYMGB) black hole. We solve the Proca
equation (PE) by applying the WKB approximation and separation of variables via
Hamilton-Jacobi (HJ) equation which results in a set of five differential
equations, and reproduces in this way, the Hawking temperature. In the second
part of this paper, we extend our results beyond the semiclassical
approximation. In particular, we derive the logarithmic correction to the
entropy of the 5D EYMGB black hole and show that the quantum corrected specific
heat indicates the possible existence of a remnant.Comment: 7 pages, accepted by EPL (Europhysics Letters
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