Journal of High Energy Physics · 2001 · 140 citations · 0 references
A new type of four-dimensional string vacua with Scherk--Schwarz supersymmetry breaking is considered. The construction involves Z_N x Z_M' freely acting orbifolds, defined in terms of rotations and translations in the internal space. Tachyons are either absent or limited to a given region of the tree-level moduli space. Particular attention is devoted to an interesting Z_3 x Z_3' heterotic example.