Selmer corank
Selmer corank is a measure of the size of an elliptic curve's Selmer group that gives an upper bound on the rank of its rational points.
Selmer corank refers to the corank of the p-adic Selmer group defined for an elliptic curve and a prime p. The Selmer group, named after Norwegian mathematician Ernst Selmer, approximates the hard-to-compute group of rational points with an object that can be calculated.
The Selmer corank is an upper bound on the algebraic rank of the elliptic curve, and the two are equal when the corresponding part of the Tate-Shafarevich group is finite. It is therefore often used in proving partial results toward the Birch and Swinnerton-Dyer conjecture.
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