2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/224846String theory in an exact plane wave background is explored. A new example of singularity in the sense of string theory for nonsingular spacetime metric is presented. The 4-tachyon scattering amplitude is constructed. The spectrum of states found from the poles in the factorization turns out to be equivalent to that of the theory in flat space-time. The massless vertex operator is obtained from the residue of the first order pole.15 pages, GTCRG-8, RevTexHigh Energy Physics - Theorytext