Adequate theory of multiverse properties and anthropic selection for the cosmological constant

Develop an adequate predictive theory describing the properties of universes in a cosmological multiverse and the associated selection effects that permit observers, in order to assess the expected distribution of Einstein’s cosmological constant Λ across life-permitting universes and compare it with the value inferred from cosmology.

Background

The essay discusses Weinberg’s anthropic reasoning for why the observed value of the cosmological constant Λ might be near the largest magnitude compatible with galaxy formation and thus with the emergence of observers. A meaningful assessment would require a quantitative theory of the multiverse that specifies how Λ varies across universes and how observer selection operates.

However, the author emphasizes that current theoretical frameworks do not provide an adequate description of the ensemble of universes or of the criteria that define life-permitting physics, leaving the anthropic explanation without the necessary theoretical underpinning for quantitative tests.