Target Space Duality of Non-Supersymmetric String Theory

T-dualities of the non-supersymmetric string models, which are constructed by twisted compactifications, are investigated. We show that the T-duality groups of such models are obtained by imposing congruence conditions on $O\left( d_{L},d_{R},\mathbb{Z}\right) $, that is, the non-supersymmetric string models are invariant under congruence subgroups of $O\left( d_{L},d_{R},\mathbb{Z}\right)$. We also point out that the transitions among the non-supersymmetric models can be induced by acting $O\left( d_{L},d_{R},\mathbb{Z}\right) $ transformations.