2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179344Noncommutative ϕ^3 field theory in six dimensions exhibits the logarithmic UV/IR mixing at the two-loop order. We show that open string theory in the presence of constant background NS-NS two-form field yields the same amplitude upon taking a decoupling limit. The stretched string picture proposed on the basis of one-loop analysis naturally generalizes to the two-loop amplitudes in consideration. Our string theory formulation can incorporate the closed string insertions as well as open string insertions. Furthermore, the analysis of the world-sheet partition function and propagators can be straightforwardly generalized to Riemann surfaces with genus zero but with an arbitrary number of boundaries.25 pages, 3 figures; v2. a reference added and typos corrected. Version to appear in Nuclear Physics BHigh Energy Physics - Theorytext