New constraints on cosmological modified gravity theories from anisotropic three-point correlation functions of BOSS DR12 galaxies

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We report a new test of modified gravity theories using the large-scale structure of the Universe.

• This paper is the first attempt to (1) apply a joint analysis of the anisotropic components of galaxy two- and three-point correlation functions (2 and 3PCFs) to actual galaxy data and (2) constrain the nonlinear effects of degenerate higher-order scalar-tensor (DHOST) theories on cosmological scales.
• Applying this analysis to the Baryon Oscillation Spectroscopic Survey (BOSS) data release 12, we obtain the lower bounds of $-1.655 < \xi_{\rm t}$ and $-0.504 < \xi_{\rm s}$ at the $95\%$ confidence level on the parameters characterising the time evolution of the tidal and shift terms of the second-order velocity field.
• These constraints are consistent with GR predictions of $\xi_{\rm t}=15/1144$ and $\xi_{\rm s}=0$.