A note on the 2-part of K2(oF) for totally real number fields F

On Shintani’s ray class invariant for totally real number fields

We introduce a ray class invariant X(C) for a totally real field, following Shintani’s work in the real quadratic case. We prove a factorization formula X(C) = X1(C) · · ·Xn(C) where each Xi(C) corresponds to a real place (Theorem 3.5). Although this factorization depends a priori on some choices (especially on a cone decomposition), we can show that it is actually independent of these choices ...

Perfect Forms over Totally Real Number Fields

A rational positive-definite quadratic form is perfect if it can be reconstructed from the knowledge of its minimal nonzero value m and the finite set of integral vectors v such that f(v) = m. This concept was introduced by Voronöı and later generalized by Koecher to arbitrary number fields. One knows that up to a natural “change of variables” equivalence, there are only finitely many perfect f...

A Note on the Pythagoras Number of Real Function Fields

We show that the pythagoras number of a real function field is strictly larger than its transcendence degree. In the purely transcendental case, this is a well known consequence of the Cassels-Pfister Theorem.

Gross–Stark units for totally real number fields

Computing a Lower Bound for the Canonical Height on Elliptic Curves over Totally Real Number Fields

Computing a lower bound for the canonical height is a crucial step in determining a Mordell–Weil basis of an elliptic curve. This paper presents a new algorithm for computing such lower bound, which can be applied to any elliptic curves over totally real number fields. The algorithm is illustrated via some examples.