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Paper   IPM / Physic / 16709
School of Physics
  Title:   Can dark energy be dynamical?
1.  E. O. Colgain
2.  M.M. Sheikh-Jabbari
3.  L. Yin
  Status:   Published
  Journal: Phys. Rev. D
  Vol.:  104
  Year:  2021
  Pages:   023510
  Supported by:  IPM
We highlight shortcomings of the dynamical dark energy (DDE) paradigm. For parametric models with equation of state (EOS), w(z) = w0 + wa f(z) for a given function of redshift f(z), we show that the errors in wa are sensitive to f(z): if f(z) increases quickly with redshift z, then errors in wa are smaller, and vice versa. As a result, parametric DDE models suffer from a degree of arbitrariness and focusing too much on one model runs the risk that DDE may be overlooked. In particular, we show the ubiquitous Chevallier-Polarski-Linder model is one of the least sensitive to DDE. We also comment on "wiggles" in w(z) uncovered in non-parametric reconstructions. Concretely, we isolate the most relevant Fourier modes in the wiggles, model them and fit them back to the original data to confirm the wiggles at <~2σ. We delve into the assumptions going into the reconstruction and argue that the assumed correlations, which clearly influence the wiggles, place strong constraints on field theory models of DDE.

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