A Symmetry of Cosmological Observables, and a High Hubble Constant as an
  Indicator of a Mirror World Dark Sector
  We point out a previously unnoticed symmetry of many important cosmological
observables and show that a cosmological model with a "mirror world" dark
sector can exploit this symmetry to completely eliminate the Hubble tension.
Our work motivates searches for both a more detailed particle physics model
that satisfies laboratory constraints and a means of increasing the cosmic
photon scattering rate that respects observational bounds on the primordial
helium abundance.
