2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56380Using sigma-model approach, we study a class of coset spaces with torsion which compactify the D=26 closed bose-string theory. Requiring also that massless chiral fermions arise from the geometry/topology of coset space, we are left with the unique possibility: it implies D=14 subcritical dimensions and the isometry group G_2 X G_2.7 pages, uses hip-artc.sty; V2: misprint corrected, references added; V3: reference corrected. Talk given at 2nd Int.Conf. "Non-Euclidean Geometry in Modern Physics" (Nyiregyhaza, Hungary, July 1999)High Energy Physics - TheoryGeneral Relativity and Quantum CosmologyHigh Energy Physics - Phenomenologytext