A smooth projective curve over the complex numbers is determined up to isomorphism by its Jacobian variety together with its canonical principal polarization of a complex torus. For genus at least three, the branch locus of the theta Gauss map recovers the canonical curve by projective biduality theorem, or recovers the canonical rational normal curve and the branch points of a hyperelliptic curve. In genus two the theta divisor itself is the curve; in genus one the Jacobian variety is the curve after choosing an origin. The polarization is essential data in this statement.
The Torelli theorem is a fundamental result in algebraic geometry and the theory of Riemann surfaces, attributed to the mathematician Carlo Alberto Torelli. It essentially describes the relationship between the algebraic structure of a curve and its deformation in terms of its Jacobian.
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