Existence of environments yielding large medium-dependent effects on gravitational-wave propagation via cancellation

Determine whether there exist physical environments in which a cancellation analogous to the atomic polarizability cancellation in electromagnetism occurs for gravitational interactions, thereby making medium-dependent effects on gravitational-wave propagation surprisingly large.

Background

The essay discusses the 2019 calculation by Flauger and Weinberg of gravitational-wave absorption in hot interstellar gas, highlighting that although low-frequency absorption scales strongly with frequency, it is largely cancelled by stimulated emission, rendering the Universe transparent to gravitational waves at observable scales.

Drawing an analogy with electromagnetism, where medium-dependent propagation effects can be large due to a cancellation in atomic polarizability that removes explicit dependence on the electromagnetic coupling, the author speculates about the gravitational counterpart. The explicit unresolved question asks whether a similar cancellation could occur for gravity, leading to unexpectedly large medium-dependent effects on gravitational-wave propagation.