A Ratio-Preserving Approach to Cosmological Concordance

Understand

Cosmological observables are particularly sensitive to key ratios of energy densities and rates, both today and at earlier epochs of the Universe.

• Well-known examples include the photon-to-baryon and the matter-to-radiation ratios.
• Equally important, though less publicized, are the ratios of pressure-supported to pressureless matter and the Thomson scattering rate to the Hubble rate around recombination, both of which observations tightly constrain.
• Preserving these key ratios in theories beyond the $\Lambda$ Cold-Dark-Matter ($\Lambda$CDM) model ensures broad concordance with a large swath of datasets when addressing cosmological tensions.