We study mirror symmetry of type II strings on manifolds with the exceptional holonomy groups G 2 and Spin(7). Our central result is a construction of mirrors of Spin(7) manifolds realized as generalized connected sums. In parallel to twisted connected sum G 2 manifolds, mirrors of such Spin(7) manifolds can be found by applying mirror symmetry to the pair of non-compact manifolds they are glued from. To provide non-trivial checks for such geometric mirror constructions, we give a CFT analysis of mirror maps for Joyce orbifolds in several new instances for both the Spin(7) and the G 2 case. For all of these models we find possible assignments of discrete torsion phases, work out the action of mirror symmetry, and confirm the consistency with the geometrical construction. A novel feature appearing in the examples we analyse is the possibility of frozen singularities.

No abstract

We write down the Algebraic Bethe Ansatz for string theory on AdS 3 × S 3 × T 4 and AdS 3 × S 3 × K3 in its orbifold limits. We use it to determine the wave-functions of protected closed strings in these backgrounds and prove that their energies are protected to all orders in α ′ . We further apply the ABA to find the wave functions of protected states of AdS 3 × S 3 × S 3 × S 1 and its Z 2 orbifold. Our findings match with protected spectrum calculations from supergravity, Sym N orbifolds and apply to the complete moduli space of these theories, excluding orbifold blow-up modes for which further analysis is necessary.

No abstract

No abstract