Constraining GR alternatives with astrophysical probes

Determine whether astrophysical observations can significantly reduce the viable theory space of alternatives to General Relativity, including whether ringdown observations will be sufficiently precise to distinguish quasinormal modes of GR from those of alternative theories and whether environmental effects can be disentangled from genuine deviations.

Background

Quadratic gravity and Lorentz-violating theories predict modified black hole spectra and causal structures (multiple horizons, universal horizons). Observations of inspiral and ringdown provide stringent tests, but environmental factors can mimic deviations.

This open question asks how far future data can conclusively narrow or falsify GR alternatives.