Scaling solutions and weak gravity in dark energy with energy and momentum couplings

Luca Amendola, Shinji Tsujikawa

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


We argue that the ΛCDM tensions of the Hubble-Lematre expansion rate H0 and the clustering normalization σ8 can be eased, at least in principle, by considering an interaction between dark energy and dark matter in such a way to induce a small and positive early effective equation of state and a weaker gravity. For a dark energy scalar field φ interacting with dark matter through an exchange of both energy and momentum, we derive a general form of the Lagrangian allowing for the presence of scaling solutions. In a subclass of such interacting theories, we show the existence of a scaling φ-matter-dominated-era (φMDE) which can potentially alleviate the H0 tension by generating an effective high-redshift equation of state. We also study the evolution of perturbations for a model with φMDE followed by cosmic acceleration and find that the effective gravitational coupling relevant to the linear growth of large-scale structures can be smaller than the Newton gravitational constant G at low redshifts. The momentum exchange between dark energy and dark matter plays a crucial role for realizing weak gravity, while the energy transfer is also required for the existence of φMDE.

Original languageEnglish
Article number020
JournalJournal of Cosmology and Astroparticle Physics
Issue number6
Publication statusPublished - 2020 Jun


  • dark energy theory
  • modified gravity

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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