Palindromy and Ambiguous Ideals Revisited Original Research Article

The purpose of this article is to revisit the relationship between ambiguous ideals and palindromy in the simple continued fraction expansions of quadratic irrationals begun by the first author and A. J. van der Poorten (1995,Bull. Austral. Math. Soc.51, 215–233). We present simpler proofs of known results, new interrelationships, and correct some misinterpretations. We do this via the infrastructure of real quadratic fields. The conclusion is that palindromy is ambiguity, when properly viewed.