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Giant Gravitons Intersecting at Angles from Integrable Spin Chains

We study integrable non-diagonal open boundary conditions for spin chains arising from holographic gauge theories. Their dual description is in terms of open strings stretching between giant gravitons intersecting at arbitrary angles inside spheres or projective spaces. By studying properties of their ground and low-lying states we reproduce the expected spectrum near the intersections. Unlike the case of intersecting D-branes in flat space, intersecting giant gravitons related by $SU(N)$ rotations do not always preserve an additional supersymmetry. We quantify this lack of enhancement by whether or not there exists a simple ferromagnetic ground state for the open spin chain.