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- Tobias Basse, Denmark
- Ole Eggers Bjælde
- Jan Hamann, Theory Division, Physics Department, CERN, Denmark
- Steen Hannestad
- Yvonne Y. Y. Wong, School of Physics, The University of New South Wales

We perform a detailed forecast on how well a Euclid-like survey will be
able to constrain dark energy and neutrino parameters from a combination
of its cosmic shear power spectrum, galaxy power spectrum, and cluster
mass function measurements. We find that the combination of these three
probes vastly improves the survey's potential to measure the time
evolution of dark energy. In terms of a dark energy figure-of-merit
defined as
(σ(wp)σ(wa))‑1, we
find a value of 690 for Euclid-like data combined with Planck-like
measurements of the cosmic microwave background anisotropies in a
10-dimensional cosmological parameter space, assuming a ΛCDM
fiducial cosmology. For the more commonly used 7-parameter model, we
find a figure-of-merit of 1900 for the same data combination. We
consider also the survey's potential to measure dark energy
perturbations in models wherein the dark energy is parameterised as a
fluid with a nonstandard non-adiabatic sound speed, and find that in an
optimistic scenario in which w0 deviates from -1 by as much
as is currently observationally allowed, models with hat
cs2 = 10‑6 and hat
cs2 = 1 can be distinguished from one another at
more than 2σ significance. We emphasise that constraints on the
dark energy sound speed from cluster measurements are strongly dependent
on the modelling of the cluster mass function; significantly weaker
sensitivities ensue if we modify our model to include fewer features of
nonlinear dark energy clustering. Finally, we find that the sum of
neutrino masses can be measured with a 1σ precision of 0.015 eV,
even in complex cosmological models in which the dark energy equation of
state varies with time. The 1σ sensitivity to the effective number
of relativistic species Neffml is approximately
0.03, meaning that the small deviation of 0.046 from 3 in the standard
value of Neffml due to non-instantaneous
decoupling and finite temperature effects can be probed with 1σ
precision for the first time.

Original language | English |
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Article number | 021 |

Journal | Journal of Cosmology and Astroparticle Physics |

Volume | 05 |

Number of pages | 25 |

ISSN | 1475-7516 |

DOIs | |

Publication status | Published - 1 May 2014 |

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