3 years ago

Matter bispectrum beyond Horndeski.

Hiroyuki Tashiro, Tsutomu Kobayashi, Shuichiro Yokoyama, Shin'ichi Hirano

The Horndeski scalar-tensor theory and its recent extensions allow nonlinear derivative interactions of the scalar degree of freedom. We study the matter bispectrum of large scale structure as a probe of these modified gravity theories, focusing in particular on the effect of the terms that newly appear in the so-called "beyond Horndeski" theories. We derive the second-order solution for the matter density perturbations and find that the interactions beyond Horndeski lead to a new time-dependent coefficient in the second-order kernel which differs in general from the standard value of general relativity and the Horndeski theory. This can deform the matter bispectrum at the folded triangle configurations ($k_1+k_2=k_3$), while it is never possible within the Horndeski theory.

Publisher URL: http://arxiv.org/abs/1801.07885

DOI: arXiv:1801.07885v1

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