2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67167A K3 surface is a quaternionic analogue of an elliptic curve from a view point of moduli of vector bundles. We can prove the algebraicity of certain Hodge cycles and a rigidity of curve of genus eleven and gives two kind of descriptions of Fano threefolds as applications. In the final section we discuss a simplified construction of moduli spaces.Algebraic Geometry14J10, 14J28, 14J60text