Efficient Computation of CMB anisotropies in closed FRW models

TL;DR

The paper develops a fast, polarization-inclusive framework for computing CMB anisotropies in closed FRW universes, extending line-of-sight methods within a 1+3 covariant perturbation formalism. It delivers a discretized, numerically stable implementation that handles scalar and tensor perturbations in curved geometries, including hyperspherical Bessel functions and curvature-adjusted sampling. The authors present results showing curvature-induced shifts in power and enhanced large-scale ISW effects, plus a suppression of tensor quadrupole due to spectral cutoffs, and validate the approach against CMBFAST. A public Fortran 90 code enables efficient exploration of the full parameter space, including curvature, across cosmological models.

Abstract

We implement the efficient line of sight method to calculate the anisotropy and polarization of the cosmic microwave background for scalar and tensor modes in almost-Friedmann-Robertson-Walker models with positive spatial curvature. We present new results for the polarization power spectra in such models.