Cosmological perturbations: non-cold relics without the Boltzmann hierarchy

Abstract

We present a formulation of cosmological perturbation theory where the Boltzmann hierarchies that evolve the neutrino phase-space distributions are replaced by integrals that can be evaluated easily with fast Fourier transforms. The simultaneous evaluation of these integrals combined with the differential equations for the rest of the system (dark matter, photons, baryons) are then solved with an iterative scheme that converges quickly. The formulation is particularly powerful for massive neutrinos, where the effective phase space is three-dimensional rather than two-dimensional, and even moreso for three different neutrino mass eigenstates. Therefore, it has the potential to significantly speed up the computation times of cosmological-perturbation calculations. This approach should also be applicable to models with other non-cold collisionless relics.

5 pages, 3 figures

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• Lyman-$\alpha$ constraints on freeze-in and superWIMPs
• Imprints of Relic Gravitational Waves in Cosmic Microwave Background Radiation
• What can CMB observations tell us about the neutrino distribution function?
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Cited by in corpus (6)

• Probing neutrino interactions and dark radiation with gravitational waves
• An accurate fluid approximation for massive neutrinos in cosmology
• Structure Formation with Warm White Noise: Effects of Finite Number Density and Velocity Dispersion in Particle and Wave Dark Matter
• Enhanced Small-Scale Structure in the Cosmic Dark Ages
• Rapid and accurate numerical evolution of linear cosmological perturbations with non-cold relics
• Slow neutrinos: non-linearity and momentum-space emulation