Unique gravitational wave signatures of GLPV scalar-tensor theories
Abstract
We study gravitational waves induced by scalar primordial fluctuations in Gleyzes-Langlois-Piazza-Vernizzi (GLPV), beyond Horndeski, scalar-tensor theories. We uncover, at the level of the action, a new scalar-scalar-tensor interaction, unique to GLPV models disconnected from Horndeski via disformal transformation. The new interaction, arising in the unitary-degenerate (U-DHOST) sector of GLPV, leads to third derivatives in the source for scalar-induced tensor modes, which are absent in Horndeski-related theories. Such new higher-derivative terms lead to a further enhanced production of induced gravitational waves. We predict that for a scale-invariant primordial spectrum, the induced gravitational wave spectral density has a characteristic frequency dependence proportional to . Such a fast-rising spectrum offers a potential unique signature of modified gravity in the early universe.
Keywords
Cite
@article{arxiv.2509.05027,
title = {Unique gravitational wave signatures of GLPV scalar-tensor theories},
author = {Guillem Domènech and Alexander Ganz and Mohammad Ali Gorji and Masahide Yamaguchi},
journal= {arXiv preprint arXiv:2509.05027},
year = {2026}
}
Comments
36 pages, 3 figures; accepted version