Bibliographic Details
| Title: |
Fast computation of temperature and polarization coupling matrices. |
| Authors: |
Kiddier, Georgia1 (AUTHOR), Gratton, Steven2 (AUTHOR) |
| Source: |
Monthly Notices of the Royal Astronomical Society. 7/10/2026, Vol. 549 Issue 4, p1-9. 9p. |
| Subject Terms: |
*Cosmic background radiation, *Parallel programming, *Numerical analysis |
| Abstract: |
We present a fast and exact method for computing cosmic microwave background (CMB) mode-coupling matrices based on an optimized evaluation of Wigner– 3 j symbols. The method exploits analytic structure in the relevant Wigner– 3 j symbol configurations appearing in temperature and polarization coupling matrices, expressing all required quantities in terms of a small set of recurrence-generated values which are pre-computed and stored in lookup tables. This approach reduces the computational cost of constructing the full coupling matrices while maintaining numerical accuracy. We demonstrate the performance of the threej_cosmo implementation using realistic survey masks from current CMB experiments. Relative to standard recursion-based approaches used in existing pseudo- C ℓ pipelines, the method achieves speedups of 6– 25 × in practical coupling-matrix constructions, with the largest gains occurring at high multipoles. The algorithm admits efficient parallelization on both CPUs and GPUs, the latter providing additional acceleration, up to a further O (50) on modern hardware, without altering the underlying formalism. Beyond full matrix construction, the approach is naturally suited to applications in which only a restricted set of ℓ 3 modes is required for each (ℓ 1 , ℓ 2) pair, such as in the computation of band-limited coupling matrices and analytic covariance terms. These features make threej_cosmo a practical backend for pseudo- C ℓ estimation and related calculations in next-generation CMB analysis pipelines. [ABSTRACT FROM AUTHOR] |
| Database: |
Academic Search Index |