Sector-Resolved Bayesian Model Averaging for DESI-Era Cosmology

We present a quotient-space Bayesian formulation for DESI-era anomaly interpretation. Given a pattern-labeled catalog with map (i\mapsto \Act(i)), the induced posterior (p(\Act\mid D)), sector inclusion probabilities (P_α), co-activation probabilities (P_{αβ}), and grouped Bayes factors (B_α(D)) are exact summaries over predeclared physical activation events. Pairwise comparisons such as (\lcdm) versus (\wacdm) remain ordinary Bayes-factor tests between specified families; the quotient construction addresses the coarser question of which physical sector carries posterior support when different sectors are represented by unequal numbers of catalog elements. We derive a sector-resolved DESI-CMB-SN likelihood specification for late-time background, early-time ruler, supernova calibration, perturbation, and gravitational-wave propagation sectors. The construction includes an Alcock-Paczynski/isotropic-scale BAO decomposition, a pure-ruler projection, analytic marginalization of low-rank supernova calibration modes, Fisher-normalized sector priors, inactive-sector leakage tests, log-evidence uncertainty propagation, and prior/sector-partition diagnostics. The result is a quantitative procedure for reporting model-comparison support at the level of physically interpretable sectors.

Source: arXiv:2609.09045v1 - http://arxiv.org/abs/2609.09045v1 PDF: https://arxiv.org/pdf/2609.09045v1 Original Link: http://arxiv.org/abs/2609.09045v1