1,957 research outputs found
Self-force via Green functions and worldline integration
A compact object moving in curved spacetime interacts with its own
gravitational field. This leads to both dissipative and conservative
corrections to the motion, which can be interpreted as a self-force acting on
the object. The original formalism describing this self-force relied heavily on
the Green function of the linear differential operator that governs
gravitational perturbations. However, because the global calculation of Green
functions in non-trivial black hole spacetimes has been an open problem until
recently, alternative methods were established to calculate self-force effects
using sophisticated regularization techniques that avoid the computation of the
global Green function. We present a method for calculating the self-force that
employs the global Green function and is therefore closely modeled after the
original self-force expressions. Our quantitative method involves two stages:
(i) numerical approximation of the retarded Green function in the background
spacetime; (ii) evaluation of convolution integrals along the worldline of the
object. This novel approach can be used along arbitrary worldlines, including
those currently inaccessible to more established computational techniques.
Furthermore, it yields geometrical insight into the contributions to
self-interaction from curved geometry (back-scattering) and trapping of null
geodesics. We demonstrate the method on the motion of a scalar charge in
Schwarzschild spacetime. This toy model retains the physical history-dependence
of the self-force but avoids gauge issues and allows us to focus on basic
principles. We compute the self-field and self-force for many worldlines
including accelerated circular orbits, eccentric orbits at the separatrix, and
radial infall. This method, closely modeled after the original formalism,
provides a promising complementary approach to the self-force problem.Comment: 18 pages, 9 figure
Charge and mass effects on the evaporation of higher-dimensional rotating black holes
To study the dynamics of discharge of a brane black hole in TeV gravity
scenarios, we obtain the approximate electromagnetic field due to the charged
black hole, by solving Maxwell's equations perturbatively on the brane. In
addition, arguments are given for brane metric corrections due to backreaction.
We couple brane scalar and brane fermion fields with non-zero mass and charge
to the background, and study the Hawking radiation process using well known low
energy approximations as well as a WKB approximation in the high energy limit.
We argue that contrary to common claims, the initial evaporation is not
dominated by fast Schwinger discharge.Comment: Published version. Minor typos corrected. 29 pages, 5 figure
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