The Quarterly Journal of Mathematics Advance Access published online on February 1, 2009
The Quarterly Journal of Mathematics, doi:10.1093/qmath/hap001
TATE–SHAFAREVICH GROUPS AND FROBENIUS FIELDS OF REDUCTIONS OF ELLIPTIC CURVES

Department of Computing, Macquarie University, Sydney, NSW 2109, Australia
E-mail: igor{at}ics.mq.edu.au
Received 16 September 2008; Accepted for publication 5 January 2009.
| Abstract |
|---|
Let E/
be a fixed elliptic curve over
which does not have complex multiplication. Assuming the Generalized Riemann Hypothesis, Cojocaru and Duke have obtained an asymptotic formula for the number of primes p
x such that the reduction of E modulo p has a trivial Tate–Shafarevich group. Recent results of Cojocaru and David lead to a better error term. We introduce a new argument in the scheme of the proof, which gives a further improvement.