CMBolic: New Symbolic Emulator for Cosmic Microwave Background Lensing Analysis
Researchers have introduced CMBolic, a suite of symbolic emulators for the Cosmic Microwave Background (CMB) lensing potential power spectrum that replaces traditional neural network approaches with analytic functions. The tool targets the extended ΛCDM cosmological model, incorporating massive neutrinos and evolving dark energy, and achieves mean absolute fractional errors of 0.27–0.32% on validation data. This matters because it dramatically reduces Bayesian parameter estimation runtimes while maintaining precision below the noise thresholds of next-generation CMB Stage 4 experiments.
CMBolic is a newly presented suite of symbolic CMB emulators designed to compute the lensing potential power spectrum across multipole ranges from 2 to 5500. Unlike neural network emulators, CMBolic produces analytic functions of cosmological model parameters, making the tool more transparent and easier to handle. The emulator operates within the extended ΛCDM framework, simultaneously accounting for massive neutrinos and evolving dark energy described by the Chevallier-Polarski-Linder parameterization. Validation tests show mean absolute fractional errors of 0.27% in the standard ΛCDM subspace and 0.32% across the full extended parameter space—well within the precision requirements of upcoming CMB Stage 4 experiments. The authors applied CMBolic to cosmological parameter estimation using lensing-only likelihoods from ACT DR6 and Planck, finding excellent agreement with the established Boltzmann code CLASS. The most striking practical benefit is computational speed: tasks that previously required approximately two weeks of runtime can now be completed in under three minutes. The code has been made publicly available alongside the paper.
What's missing
The paper is a preprint and has not yet undergone formal peer review. Key open questions include how CMBolic performs on CMB temperature and polarization power spectra beyond lensing, and whether the analytic approximations degrade in extreme or non-standard cosmological scenarios outside the tested parameter ranges.
What different sources said
- arXiv astro-phCenter
CMBolic: Symbolic emulators for the Cosmic Microwave Background. I. Lensing
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