From a quickscan it seems the theoretical basis for the work is revisiting how one stiches together relativistic descriptions of compact objects to cosmological solutions. This cannot be done exactly, some approximation is required. The authors revisit the perturbation theory that was used in classic papers and argue an alternative approach that effectively brings additional "physics". In their first paper [0] they suggest that binary neutron stars, being a relativistic compact object should also exhibit "cosmological coupling". Not clear where this stands.
Comments
From a quickscan it seems the theoretical basis for the work is revisiting how one stiches together relativistic descriptions of compact objects to cosmological solutions. This cannot be done exactly, some approximation is required. The authors revisit the perturbation theory that was used in classic papers and argue an alternative approach that effectively brings additional "physics". In their first paper [0] they suggest that binary neutron stars, being a relativistic compact object should also exhibit "cosmological coupling". Not clear where this stands.
[0] https://iopscience.iop.org/article/10.3847/1538-4357/ab32da