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arXiv · 2606.20730

Scalar-scalar-tensor interaction in DHOST theories

S. Mironov·V. Volkova
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Abstract

We derive the general cubic action for perturbations about a cosmological background in the quadratic subclass of degenerate higher-order scalar-tensor (DHOST) theories, focusing on scalar-scalar-tensor interactions. We adopt a fully covariant formulation and implement unitary gauge at the level of perturbations. This mixed sector provides the key ingredient for estimating the decay rate of a gravitational wave into two scalar excitations in the quadratic DHOST models of dark energy in the late-time Universe.

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S. Mironov, V. Volkova. 2026-06-17. Scalar-scalar-tensor interaction in DHOST theories. https://doi.org/10.4213/tmf11205

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