Exact half-BPS string-junction solutions in six-dimensional supergravity

We construct SO(2, 1) x SO(3)-invariant half-BPS solutions in six-dimensional (0,4) supergravity with m tensor multiplets. The space-time manifold of each one of these solutions consists of an AdS(2) x S-2 warped over a Riemann surface Sigma with boundary. The most general local solution is parametrized by one real harmonic function, and m + 2 holomorphic functions which are subject to a quadratic constraint and a hermitian inequality, both of which are manifestly SO(2, m) invariant. Imposing suitable conditions on these harmonic and holomorphic functions, we construct globally regular supergravity solutions with N distinct AdS(3) x S-3 asymptotic regions and contractible Sigma. These solutions have an intricate moduli space, whose dimension equals 2(m + 1) N - m - 2 and matches the counting of three-form charge vectors and un-attracted scalars of the tensor multiplet. Exact explicit formulas for all supergravity fields are obtained in terms of the moduli. Our solutions give the near-horizon geometries for junctions of N self-dual strings in six dimensions, and are holographic duals to CFTs defined on N half-planes which share a common interface line. For m = 5, the solutions lift to quarter-BPS solutions for six-dimensional (4,4) supergravity.