SFB power spectrum emulator: Understanding the structure of our universe with the spherical Fourier-Bessel basis

The SFB power spectrum emulator is a spherical Fourier-Bessel (SFB) emulator which enables inference of cosmological parameters, motivated by SPHEREx’s (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) goal to constrain primordial non-Gaussianity and model time evolving dark energy. The emulator will intake real sky data, and use the SFB basis to produce a likelihood distribution of cosmological parameters. To construct the emulator, we sampled a large range of cosmological parameters with primordial non-Gaussianity, fNL, and bias parameter modeling, which was used to generate the over 100,000 SFB power spectra for neural network training. Our emulator will provide a rapidly iterable surrogate for classical Boltzmann solvers, and increased accuracy in constraining cosmological parameters by enabling improved data isolation and mode cuts. Future applications include applying our SFB power spectrum emulator to eBOSS cosmological surveys, and applications to SPHEREx to forecast their sensitivity to dark energy parameters, namely w₀ and w_a.