Allowed Ranges and Priors for Fundamental Parameters in Fine‑Tuning Analyses

Determine whether the Planck mass scale provides the correct cutoff for parameter values considered in fine‑tuning studies, ascertain the actual span of allowed values for other fundamental parameters, and characterize whether the prior probability distribution over these allowed values is uniform or otherwise.

Background

Quantifying fine‑tuning probabilistically depends on defining a finite, well‑motivated parameter space and a prior over it. The paper highlights that assuming infinite ranges renders probabilities ill‑defined, motivating suggestions to restrict ranges (e.g., below the Planck scale).

However, the appropriateness of such cutoffs, the true span of allowed values for other parameters, and the correct prior over those values remain unsettled, undermining precise fine‑tuning estimates.