2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189519The four-dimensional N=2 STU model of string compactification is invariant under an SL(2,Z)_S x SL(2,Z)_T x SL(2,Z)_U duality acting on the dilaton/axion S, complex Kahler form T and the complex structure fields U, and also under a string/string/string triality S-T-U. The model admits an extremal black hole solution with four electric and four magnetic charges whose entropy must respect these symmetries. It is given by the square root of the hyperdeterminant introduced by Cayley in 1845. This also features in three-qubit quantum entanglement.Minor improvements. 9 pages latexHigh Energy Physics - TheoryGeneral Relativity and Quantum CosmologyMathematical PhysicsQuantum Physicstext