Post-Newtonian parameter γ in generalized non-local gravity

We investigate the post-Newtonian parameter γ and derive its formalism in generalized non-local（GNL） gravity, which is the modified theory of general relativity（GR） obtained by adding a term m2n-2R□（-n）R to the Einstein-Hilbert action. Concretely,based on parametrizing the generalized non-local action in which gravity is described by a series of dynamical scalar fields φi in addition to the metric tensor gμν, the post-Newtonian limit is computed, and the effective gravitational constant as well as the post-Newtonian parameters are directly obtained from the generalized non-local gravity. Moreover, by discussing the values of the parametrized post-Newtonian parameters γ, we can compare our expressions and results with those in Hohmann and Jrv et al.（2016）, as well as current observational constraints on the values of γ in Will（2006）. Hence, we draw restrictions on the nonminimal coupling terms F around their background values.