Published online by Cambridge University Press: 20 November 2018
Let ${{E}_{/\mathbb{Q}}}$ be an elliptic curve with good ordinary reduction at a prime
$p\,>\,2$ . It has a welldefined Iwasawa
$\mu $ -invariant
$\mu {{\left( E \right)}_{p}}$ which encodes part of the information about the growth of the Selmer group
$\text{Se}{{\text{l}}_{{{p}^{\infty }}}}\left( {{E}_{/{{K}_{n}}}} \right)$ as
${{K}_{n}}$ ranges over the subfields of the cyclotomic
${{\mathbb{Z}}_{p}}$ -extension
${{K}_{\infty }}/\mathbb{Q}$ . Ralph Greenberg has conjectured that any such
$E$ is isogenous to a curve
${E}'$ with
$\mu {{\left( {{E}'} \right)}_{p}}\,=\,0$ . In this paper we prove Greenberg's conjecture for infinitely many curves
$E$ with a rational
$p$ -torsion point,
$p$ = 3 or 5, no two of our examples having isomorphic
$p$ -torsion. The core of our strategy is a partial explicit evaluation of the global duality pairing for finite flat group schemes over rings of integers.