2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/50272We construct modular invariant partition functions for type II strings on a conifold and a singular Eguchi-Hanson instanton by means of the SL(2,R)/U(1) version of Gepner models. In the conifold case, we find an extra massless hypermultiplet in the IIB spectrum and argue that it may be identified as a soliton. In the Eguchi-Hanson case, our formula is new and different from the earlier result, in particular does not contain graviton. The lightest IIB fields are combined into a six-dimensional (2,0) tensor multiplet with a negative mass square. We give an interpretation to it as a doubleton-like mode.13 pages, 1 figure, latex2e; typos corrected, minor changes in textHigh Energy Physics - Theorytext