Heegner's lemma

In mathematics, Heegner's lemma is a lemma used by Kurt Heegner in his paper on the class number problem. His lemma states that if

y^2=a_4x^4+a_3x^3+a_2x^2+a_1x+a_0 \,

is a curve over a field with a₄ not a square, then it has a solution if it has a solution in an extension of odd degree.

References

Birch, Bryan (2004), "Heegner points: the beginnings", in Darmon, Henri; Zhang, Shou-Wu, Heegner points and Rankin L-series, Math. Sci. Res. Inst. Publ. 49, Cambridge University Press, pp. 1–10, doi:10.1017/CBO9780511756375.002, ISBN 978-0-521-83659-3, MR 2083207