Comment on “Relation between scattering amplitude and Bethe-Salpeter wave function in quantum field theory”

In a recent article [1], Yamazaki and Kuramashi present a theoretical analysis on the "relation between scattering amplitude and Bethe-Salpeter wave function in quantum field theory". In the present Comment, we point out that the discussions in Ref.[1] on the HAL QCD method [2,3,4] are trivially invalidated because of (i) the critical misunderstandings of the HAL QCD method, and/or (ii) the fatal mathematical errors.