We study in detail how neutrino perturbations can be followed in linear theory by using only terms up to l = 2 in the Boltzmann hierarchy. We provide a new approximation to the third moment and demonstrate that the neutrino power spectrum can be calculated to a precision of better than 5% for masses up to 1 eV and k less than or similar to 10 h/Mpc. The matter power spectrum can be calculated far more precisely and typically at least a factor of a few better than with existing approximations. We then proceed to study how the neutrino power spectrum can be reliably calculated even in the non-linear regime by using the non-linear gravitational potential, sourced by dark matter overdensities, as it is derived from semi analytic methods based on N-body simulations in the Boltzmann evolution hierarchy. Our results agree extremely well with results derived from N-body simulations that include cold dark matter and neutrinos as independent particles with different properties.

Efficient calculation of cosmological neutrino clustering in the non-linear regime / M. Archidiacono, S. Hannestad. - In: JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS. - ISSN 1475-7516. - :6(2016), pp. 018.1-018.14. [10.1088/1475-7516/2016/06/018]

Efficient calculation of cosmological neutrino clustering in the non-linear regime

M. Archidiacono;
2016

Abstract

We study in detail how neutrino perturbations can be followed in linear theory by using only terms up to l = 2 in the Boltzmann hierarchy. We provide a new approximation to the third moment and demonstrate that the neutrino power spectrum can be calculated to a precision of better than 5% for masses up to 1 eV and k less than or similar to 10 h/Mpc. The matter power spectrum can be calculated far more precisely and typically at least a factor of a few better than with existing approximations. We then proceed to study how the neutrino power spectrum can be reliably calculated even in the non-linear regime by using the non-linear gravitational potential, sourced by dark matter overdensities, as it is derived from semi analytic methods based on N-body simulations in the Boltzmann evolution hierarchy. Our results agree extremely well with results derived from N-body simulations that include cold dark matter and neutrinos as independent particles with different properties.
cosmological neutrinos; cosmological perturbation theory; power spectrum
Settore FIS/05 - Astronomia e Astrofisica
Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/704680
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