Positivity in the Sky: Constraining dark energy and modified gravity from the UV

Apr 11, 2019
7 pages
Published in:
  • Phys.Rev.D 101 (2020) 2, 021502,
  • Phys.Rev.D 102 (2020) 4, 049902 (erratum)
  • Published: Jan 23, 2020
e-Print:

Citations per year

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Abstract: (APS)
Positivity bounds—the consequences of requiring a unitary, causal, local UV completion—place strong restrictions on theories of dark energy and/or modified gravity. We derive and investigate such bounds for Horndeski scalar-tensor theories and for the first time pair these bounds with a cosmological parameter estimation analysis, using CMB, redshift space distortion, matter power spectrum, and baryon acoustic oscillation measurements from the Planck, SDSS/BOSS, and 6dF surveys. Using positivity bounds as theoretical priors, we show that their inclusion in the parameter estimation significantly improves the constraints on dark energy/modified gravity parameters. Considering as an example a specific class of models, which are particularly well-suited to illustrate the constraining power of positivity bounds, we find that these bounds eliminate over 60% of the previously allowed parameter space. We also discuss how combining positivity requirements with additional theoretical priors has the potential to further tighten these constraints: for instance, also requiring a subluminal speed of gravitational waves eliminates all but ≲1% of the previously allowed parameter space.
Note:
  • 10 pages, v3: added additional subleading corrections to the computation of positivity bounds (which only very mildly affect overall constraints)
  • gravitation: model
  • matter: power spectrum
  • dark energy
  • cosmic background radiation
  • sloan digital sky survey
  • scalar tensor
  • causality
  • unitarity
  • redshift
  • satellite: Planck