Multiscale Constraints on Dark Energy: From Pulsars and the Local Group to Cosmology

In this talk, I will explore constraints on dark energy beyond the standard cosmological frameworks, incorporating insights from binary motion and galactic dynamics. I will present a method to constrain the cosmological constant, Λ, using binary galaxy systems. The ratio between the Keplerian orbital period and TΛ≈35 Gyr determines the significance of cosmological constant effects on binary motion. For systems with periods approaching this timescale, the influence of Λ becomes significant. The Milky Way–Andromeda (M31) system, with an orbital period of ∼17 Gyr, requires the inclusion of dark energy effects. Utilizing the latest mass estimates for the Milky Way and M31, combined with proper motion data from HST and Gaia, I will demonstrate that the value of Λ inferred from Local Group dynamics is less than 5.44 times the Planck value. Furthermore, I will discuss a general framework for applying constraints to galaxy groups and clusters in the local universe.