Linear perturbations in K-mouflage cosmologies with massive neutrinos

Alexandre Barreira, Philippe Brax, Sebastien Clesse, Baojiu Li, and Patrick Valageas
Phys. Rev. D 91, 063528 – Published 24 March 2015

Abstract

We present a comprehensive derivation of linear perturbation equations for different matter species, including photons, baryons, cold dark matter, scalar fields, and massless and massive neutrinos in the presence of a generic conformal coupling. Starting from the Lagrangians, we show how the conformal transformation affects the dynamics. In particular, we discuss how to incorporate consistently the scalar coupling in the equations of the Boltzmann hierarchy for massive neutrinos and the subsequent fluid approximations. We use the recently proposed K-mouflage model as an example to demonstrate the numerical implementation of our linear perturbation equations. K-mouflage is a new mechanism to suppress the fifth force between matter particles induced by the scalar coupling, but in the linear regime the fifth force is unsuppressed and can change the clustering of different matter species in different ways. We show how the cosmic microwave background, lensing potential and matter power spectra are affected by the fifth force and find ranges of K-mouflage parameters whose effects could be seen observationally. We also find that the scalar coupling can have the nontrivial effect of shifting the amplitude of the power spectra of the lensing potential and density fluctuations in opposite directions, although both probe the overall clustering of matter. This paper can serve as a reference for those who work on generic coupled scalar field cosmology or those who are interested in the cosmological behavior of the K-mouflage model.

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  • Received 28 November 2014

DOI:https://doi.org/10.1103/PhysRevD.91.063528

© 2015 American Physical Society

Authors & Affiliations

Alexandre Barreira1,2,*, Philippe Brax3,†, Sebastien Clesse4,‡, Baojiu Li1,§, and Patrick Valageas3,∥

  • 1Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
  • 2Institute for Particle Physics Phenomenology, Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
  • 3Institut de Physique Theorique, CEA, IPhT, CNRS, URA 2306, F-91191Gif/Yvette Cedex, France
  • 4Namur Center of Complex Systems (naXys), Department of Mathematics, University of Namur, Rempart de la Vierge 8, 5000 Namur, Belgium

  • *a.m.r.barreira@durham.ac.uk
  • philippe.brax@cea.fr
  • sebastien.clesse@unamur.be
  • §baojiu.li@durham.ac.uk
  • patrick.valageas@cea.fr; Author names listed by alphabetical order.

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Issue

Vol. 91, Iss. 6 — 15 March 2015

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