Testing General Relativity in the Strong-Field Regime with Observations of Black Holes in the Electromagnetic Spectrum. (arXiv:1209.3024v1 [astro-ph.HE])

Testing General Relativity in the Strong-Field Regime with Observations of Black Holes in the Electromagnetic Spectrum. (arXiv:1209.3024v1 [astro-ph.HE]):
General relativity has been tested by many experiments, which, however,
almost exclusively probe weak spacetime curvatures. In this thesis, I create
two frameworks for testing general relativity in the strong-field regime with
observations of black holes in the electromagnetic spectrum using current or
near-future instruments. In the first part of this thesis, I design tests of
the no-hair theorem, which uniquely characterizes the nature of black holes in
general relativity in terms of their masses and spins and which states that
these compact objects are described by the Kerr metric. I investigate a
quasi-Kerr metric and construct a Kerr-like spacetime, both of which contain an
independent parameter in addition to mass and spin. If the no-hair theorem is
correct, then any deviation from the Kerr metric has to be zero. I show that
already moderate changes of the deviation parameters in either metric lead to
significant modifications of the observed signals. I apply this framework to
the imaging of supermassive black holes using very-long baseline interferometry
as well as to the quasi-periodic variability and relativistically broadened
iron lines observed in both galactic and supermassive black holes. In the
second part of this thesis, I devise a method to test the predicted evaporation
of black holes in Randall-Sundrum-type braneworld gravity through the orbital
evolution of black-hole X-ray binaries and obtain constraints on the size of
the extra dimension from A0620-00 and XTE J1118+480.