On the Interpretation of Tests of the Horizon Area Law

Abstract

This Letter investigates gravitational-wave tests of the horizon area law. Although they provide a striking consistency check of general relativity (GR), these tests rely on models that assume GR, making their interpretation inherently model dependent. We show with a specific example---simulations of merging boson stars---that exotic compact objects can mimic merging black holes and pass an area-law test at a confidence as high as $\sim 92\%$ despite not even having event horizons.