1490 BBH Simulations Reveal Merger-Rate Crisis Claims Depend on Isolated Code Frameworks
Claims of a generic BBH merger-rate crisis in isolated evolution are model-dependent. A meta-analysis of 1490 submodels finds substantial subsets match GWTC-5 rates via varied but physically motivated assumptions. Cross-framework comparisons are required before revising core binary physics.
The arXiv paper by Broekgaarden et al. aggregates rates across codes including COMPAS, COSMIC, and StarTrack, then isolates 2543 pairwise variations to rank physical assumptions. Natal kicks and common-envelope efficiency dominate variance, yet low rates also emerge from altered wind prescriptions or initial mass-ratio distributions without invoking extreme kicks. This demonstrates multiple independent pathways to observational consistency rather than a single crisis trigger.
Prevailing coverage has treated over-prediction as generic, drawing mainly from single-code ensembles that cluster in 'simulation silos.' Cross-code comparison exposes that apparent consensus within one framework fails to generalize, a pattern seen earlier in supernova kick debates where updated remnant-mass mappings resolved similar tensions without rewriting binary physics.
GWTC-5 constraints themselves carry selection biases from O4 sensitivity and redshift assumptions; future runs with improved localization will tighten the local rate interval. Multi-code projects such as COMPAS-COSMIC joint grids now underway can test whether the 20% consistency fraction holds when star-formation history and angular-momentum loss are varied uniformly.
The result reframes population synthesis as an under-constrained inverse problem where rate matching alone cannot discriminate among viable physics sets.
Broekgaarden et al.: By mid-2027, at least three independent population-synthesis codes will each produce >25% submodels inside the final O5 GWTC local rate interval when using shared initial conditions.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2606.28515)
- [2]Supporting Source(https://arxiv.org/abs/2308.03822)
- [3]Supporting Source(https://journals.aps.org/prx/abstract/10.1103/PhysRevX.13.021033)