Scale Invariant Gravity and Black Hole Ringdown
  Scale invariant theories of gravity give a compelling explanation to the
early and late time acceleration of the Universe. Unlike most scalar-tensor
theories, fifth forces are absent and it would therefore seem impossible to
distinguish scale invariant gravity from general relativity. We show that the
ringdown of a Schwarschild-de Sitter black hole may have a set of massive modes
which are characteristic of scale invariant gravity. In principle these new
modes can be used to distinguish scale invariant gravity from general
relativity. In practice, we discuss the obstacles to generating these new
massive modes and their detectability with future gravitational wave
experiments but also speculate on their role in Kerr black holes.
