The practical computation of areas associated with binary quartic forms

Abstract:

We derive formulas for practically computing the area of the region $|F(x,y)| \leq 1$ defined by a binary quartic form $F(X,Y) \in \mathbb R [X,Y]$. These formulas, which involve a particular hypergeometric function, are useful when estimating the number of lattice points in certain regions of the type $|F(x,y)| \leq h$ and will likely find application in many contexts. We also show that for forms $F$ of arbitrary degree, the maximal size of the area of the region $|F(x,y)| \leq 1$, normalized with respect to the discriminant of $F$ and taken with respect to the number of conjugate pairs of $F(x,1)$, increases as the number of conjugate pairs decreases; and we give explicit numerical values for these normalized maxima when $F$ is a quartic form.