Revisiting coupled CDM-massive neutrino perturbations in diverse cosmological backgrounds

Sourav Pal, Rickmoy Samanta, Supratik Pal

Research output: Contribution to journalArticlepeer-review


Massive neutrinos are well-known to cause a characteristic suppression in the growth of structures at scales below the neutrino free-streaming length. A detailed understanding of this suppression is essential in the era of precision cosmology we are entering into, enabling us to better constrain the total neutrino mass and possibly probe (beyond)-ΛCDM cosmological model(s). Instead of the usual N-body simulation or Boltzmann solver, in this article we consider a two-fluid framework at the linear scales, where the neutrino fluid perturbations are coupled to the CDM (+ baryon) fluid via gravity at redshifts of interest. Treating the neutrino mass fraction f ν as a perturbative parameter, we find solutions to the system with redshift-dependent neutrino free-streaming length in ΛCDM background via two separate approaches. The perturbative scale-dependent solution is shown to be in excellent agreement with numerical solution of the two-fluid equations valid to all orders in f ν, and also agrees with results from CLASS to a good accuracy. We further generalize the framework to incorporate different evolving dark energy backgrounds and found sub-percent level differences in the suppression, all of which lie within the observational uncertainty of BOSS-like surveys. We also present a brief discussion on the prospects of the current analysis in the context of upcoming missions.

Original languageEnglish
Article number004
JournalJournal of Cosmology and Astroparticle Physics
Issue number12
StatePublished - 1 Dec 2023
Externally publishedYes

Bibliographical note

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© 2023 IOP Publishing Ltd and Sissa Medialab.


  • cosmological neutrinos
  • neutrino masses from cosmology
  • power spectrum


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