L. Cooper et Ii. Kogan, BOUNDARY-CONDITIONS AND HETEROTIC CONSTRUCTION IN TOPOLOGICAL MEMBRANE THEORY, Physics letters. Section B, 383(3), 1996, pp. 271-280
Using the topological membrane approach to string theory, we suggest a
geometric origin for the heterotic string. We show how different memb
rane boundary conditions lead to different string theories. We discuss
the construction of closed oriented strings and superstrings, and dem
onstrate how the heterotic construction naturally arises from a specif
ic choice of boundary conditions on the left and right boundaries of a
cylindrical topological membrane.