From supermembrane to matrix string

We develop a systematic method of directly embedding supermembrane wrapped around a circle into matrix string theory. Our purpose is to study connection between matrix string and membrane from an entirely 11-dimensional point of view. The method does neither rely on the DLCQ limit nor on string dualities. In principle, this enables us to construct matrix string theory with arbitrary backgrounds from the corresponding supermembrane theory. As a simplest application of the formalism, the matrix-string action with a 7-brane background (Kaluza-Klein-Melvin solution) with nontrivial RR vector field is given