Dark energy and modified gravity in degenerate higher-order scalar–tensor (DHOST) theories: A review

By D. Langlois. International Journal of Modern Physics D, 2018

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This paper reviews scalar–tensor theories characterized by a Lagrangian that, despite the presence of second-order derivatives, contains a single scalar degree of freedom. These theories, known as Degenerate Higher-Order Scalar–Tensor (DHOST) theories, include Horndeski and Beyond Horndeski theories. They propagate a single scalar mode as a consequence of the degeneracy of their Lagrangian and, therefore, are not plagued by an Ostrogradsky instability. They have been fully classified up to cubic order in second-order derivatives. The study of their phenomenological consequences restricts the subclass of DHOST theories that are compatible with observations. In cosmology, these theories can be described in the language of the unified effective approach to dark energy and modified gravity. Compact objects in the context of DHOST theories are also discussed.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/9d015f00af7fc90e6453cb4efb7eadfe77746200

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Citations in the corpus

Testing modified gravity at cosmological distances with LISA standard sirens (2019, methodology): “Exploiting this property, Degenerate Higher Order Scalar-Tensor (DHOST) theories (see [85] for a recent review) have been constructed [86–88] and they represent (so far) the most general scalar-tensor theories that propagate a single scalar degree of freedom in addition to the helicity-2 mode of a m”
Horndeski theory and beyond: a review (2019, background): “The reader is referred to [157, 158] for a more complete review on this topic.”