Fundamental unit (number theory) (source code)

= Fundamental unit
{disambiguate=number theory}
{title2=$\epsilon$}
{wiki}

= Fundamental unit
{synonym}

In a real quadratic <number field>, a fundamental unit $\epsilon>1$ generates the infinite cyclic factor of its <unit group>, so every <unit> is $\pm\epsilon^n$. Existence follows from the <Dirichlet unit theorem>; choosing the positive generator of the rank-one logarithmic lattice gives this normalization.