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Testing coupled dark energy with next-generation large-scale observations

Luca Amendola, Valeria Pettorino, Claudia Quercellini, Adrian Vollmer

TL;DR

The paper tackles the question of whether a scalar-field–mediated coupling between dark energy and dark matter, parameterized by β in a coupled dark energy framework with an inverse power-law potential V=V_0 φ^{- ext{α}}, can be constrained by next-generation observations. It employs a Fisher-matrix forecast combining Planck-like CMB, Euclid-like galaxy power spectrum P(k), and weak-lensing data to forecast constraints on the parameter set Θ={β^2, α, Ω_c, h, Ω_b, n_s, log A} in a flat universe. The results show that while individual probes offer different strengths (P(k) delivering the strongest single-probe constraint, with σ(β^2)≈1.5×10^{-3}, and WL providing complementary information), their combination tightens β^2 to σ(β^2)≲3×10^{-4}, significantly improving current bounds and yielding meaningful Brans-Dicke and PPN implications. The study demonstrates the potential of future large-scale structure and CMB data to decisively test cosmological modifications to gravity, providing cosmological bounds complementary to solar-system tests. This work highlights the synergy of CMB and LSS probes for probing fundamental physics in the dark sector.

Abstract

Coupling dark energy to dark matter provides one of the simplest way to effectively modify gravity at large scales without strong constraints from local (i.e. solar system) observations. Models of coupled dark energy have been studied several times in the past and are already significantly constrained by cosmic microwave background experiments. In this paper we estimate the constraints that future large-scale observations will be able to put on the coupling and in general on all the parameters of the model. We combine cosmic microwave background, tomographic weak lensing, redshift distortions and power spectrum probes. We show that next-generation observations can improve the current constraint on the coupling to dark matter by two orders of magnitude; this constraint is complementary to the current solar-system bounds on a coupling to baryons.

Testing coupled dark energy with next-generation large-scale observations

TL;DR

The paper tackles the question of whether a scalar-field–mediated coupling between dark energy and dark matter, parameterized by β in a coupled dark energy framework with an inverse power-law potential V=V_0 φ^{- ext{α}}, can be constrained by next-generation observations. It employs a Fisher-matrix forecast combining Planck-like CMB, Euclid-like galaxy power spectrum P(k), and weak-lensing data to forecast constraints on the parameter set Θ={β^2, α, Ω_c, h, Ω_b, n_s, log A} in a flat universe. The results show that while individual probes offer different strengths (P(k) delivering the strongest single-probe constraint, with σ(β^2)≈1.5×10^{-3}, and WL providing complementary information), their combination tightens β^2 to σ(β^2)≲3×10^{-4}, significantly improving current bounds and yielding meaningful Brans-Dicke and PPN implications. The study demonstrates the potential of future large-scale structure and CMB data to decisively test cosmological modifications to gravity, providing cosmological bounds complementary to solar-system tests. This work highlights the synergy of CMB and LSS probes for probing fundamental physics in the dark sector.

Abstract

Coupling dark energy to dark matter provides one of the simplest way to effectively modify gravity at large scales without strong constraints from local (i.e. solar system) observations. Models of coupled dark energy have been studied several times in the past and are already significantly constrained by cosmic microwave background experiments. In this paper we estimate the constraints that future large-scale observations will be able to put on the coupling and in general on all the parameters of the model. We combine cosmic microwave background, tomographic weak lensing, redshift distortions and power spectrum probes. We show that next-generation observations can improve the current constraint on the coupling to dark matter by two orders of magnitude; this constraint is complementary to the current solar-system bounds on a coupling to baryons.

Paper Structure

This paper contains 8 sections, 30 equations, 12 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Coupled dark energy
  3. Methodology
  4. Results from CMB data
  5. Results for the galaxy power spectrum
  6. Results for Weak lensing
  7. Combining CMB, P(k) and WL
  8. Conclusions

Figures (12)

  • Figure 1: Evolution of $w_{\mathrm{eff}}$ for various values of $\beta$.
  • Figure 2: CMB unlensed TT temperature spectra for three values of $\beta$. Data are taken from WMAP7 Larson:2010gs.
  • Figure 3: Predicted confidence contours for the cosmological parameter set $\Theta\equiv\{\beta^{2},\alpha,\Omega_{c},h,\Omega_{b},n_{s},\log A\}$ using CMB Planck specifications.
  • Figure 4: Predicted confidence contours for the cosmological parameter set $\Theta\equiv\{\beta^{2},\alpha,\Omega_{c},h,\Omega_{b},n_{s},\log A\}$ (in black, equal to Fig. (\ref{['fig:cmb-cont']})) using CMB Planck specifications. Overplotted in dashed are the predicted confidence contours for the cosmological parameter set $\{\beta^{2},\alpha,\Omega_{c},\Omega_{b},n_{s},\log A\}$, with $h$ fixed to the reference value.
  • Figure 5: Predicted confidence contours for the cosmological parameter set $\Theta\equiv\{\beta^{2},\alpha,\Omega_{c},h,\Omega_{b},n_{s},\log A\}$ (in black, equal to fig.(\ref{['fig:fish-cont_h']})) using CMB Planck specifications. Overplotted are the predicted confidence contours for the cosmological parameter set $\{\beta^{2},\alpha,\Omega_{c},\Omega_{b},n_{s},\log A\}$ (dashed contours, with $h$ fixed to the reference values) and the cosmological parameter set $\{\beta^{2},\alpha,\Omega_{c},\Omega_{b},\log A\}$ (dotted contours, with $h$ and $n_{s}$ fixed to the reference values).
  • ...and 7 more figures