CASIMIR ENERGY FOR A PIECEWISE UNIFORM GREEN-SCHWARZ SUPERSTRING

The Casimir energy for the transverse oscillations of piecewise unifor m Green-Schwarz superstrings is investigated. We calculate first the z ero-point energy in both cases of bosonic and fermionic open strings c omposed of two or three pieces. Unlike a closed string, the Casimir en ergy of an open string can be either positive or negative. In addition , comparing to the result of a bosonic string, we also find that the C asimir energy of a superstring has the opposite value to that of a bos onic one.