About this Research Topic
On the cosmological side, while the dark matter problem is more likely due to some weakly interacting massive particles beyond the Standard Model rather than a breakdown of the laws of gravitation, the problem of dark energy is open. At the state of the facts, the accelerating expansion rate of the Universe may be explained by a small positive cosmological constant. Yet, it is possible that the actual explanation is either a breakdown of general relativity at large scales or the existence of some new field with peculiar properties.
From the astrophysical point of view, we can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a black hole with an accretion disk, and gravitational waves from black-hole binaries. A direct observational confirmation of the nature of these exotic objects could be seen as an important test of the theory in the strong-gravity regime. Deviations from the Kerr metric may be indeed expected from classical extensions of general relativity as well as from macroscopic quantum gravity effects.
The purpose of this Research Topic is to collect contributions on current and proposed tests of general relativity, focusing on cosmological scales as well as on the strong-field regime. We welcome the submission of both original research articles and topical reviews (Brief Research Report, Data Report, General Commentary, Hypothesis & Theory, Methods, Mini Review and Review, Opinion, Original Research, and Perspective).
Topics of interest to this Research Topic include but are most certainly not limited to:
• Dark-energy tests of general relativity at cosmological scales
• Tests of general relativity with gravitational waves from black-hole mergers
• Testing general relativity and alternative theories of gravity using the black-hole shadow
• Revealing the properties of rotating black holes with the vorticity of light
• Testing general relativity using X-ray data.
Keywords: General Relativity, Black Holes, Strong-Field Gravity Tests, Dark Energy, Modified Gravity, Gravitational Waves, Electromagnetic Vortices, Black-Hole Shadow
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.