We quantify a recent theorem of Wiles on class numbers of imaginary quadratic fields by proving an estimate for the number of negative fundamental discriminants down to −X whose class numbers are indivisible by a given prime and whose imaginary quadratic fields satisfy any given set of local conditions. This estimate matches the best results in the direction of the Cohen-Lenstra heuristics for the number of imaginary quadratic fields with class number indivisible by a given prime. This general result is applied to study rank 0 twists of certain elliptic curves.
BackgroundIdeal class numbers of imaginary quadratic fields have been studied since Gauss, who conjectured that for any given h, there are only finitely many negative fundamental discriminants D such that h(D) = h. The history of Gauss' Conjecture is rich. The conjecture was shown to be true by work of Heilbronn [13], who did not show how to find the imaginary quadratic fields with a given class number. Siegel [26] proved that h(−D) grows like |D| 1/2 , but did so ineffectively. In other words, for each > 0 he proved that for sufficiently large D there are positive constants c 1 and c 2 for which