Spacetimes in alternative theories of gravity

The primary science goal of BlackHoleCam is to capture and to study the image of the BH shadow in Sgr A*.
The absence of a quantum theory of gravity as part of a grand unified theory of all fundamental forces has resulted in the formulation of several alternative theories of gravity. Since the appearance of the shadow depends on the assumed theory of gravity, we can use its detailed shape to test of GR and alternative theories of gravity. In our project, we calculated the appearance of a BH in known spacetimes, either within GR or within alternative theories of gravity. The figures below show several examples of shadows of Kerr and Kerr-like axisymmetric BHs. Our goal is to build a generic numerical computational platform, coupled to GRMHD simulations, and use it to build a catalogue of BH images and emission properties in alternative theories of gravity.

The ultimate goal of BH shadow studies is to determine the theory of gravity that best describes the observations.