Exploring gravitational theories beyond Horndeski

@article{Gleyzes2014ExploringGT,
  title={Exploring gravitational theories beyond Horndeski},
  author={J'erome Gleyzes and David Langlois and Federico Piazza and Filippo Vernizzi},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2014},
  volume={2015},
  pages={018 - 018}
}
We have recently proposed a new class of gravitational scalar-tensor theories free from Ostrogradski instabilities, in ref. [1]. As they generalize Horndeski theories, or “generalized” galileons, we call them G3. These theories possess a simple formulation when the time hypersurfaces are chosen to coincide with the uniform scalar field hypersurfaces. We confirm that they contain only three propagating degrees of freedom by presenting the details of the Hamiltonian formulation. We examine the… 
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TLDR
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