2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/194778We study non-perturbative effects due to a heterotic M-theory five-brane wrapped on Calabi-Yau threefold. We show that such instantons contribute to derivative F-terms described recently by Beasley and Witten rather than to the superpotential.10 pages, Latex, minor correctionsHigh Energy Physics - Theorytext