Abstract
We consider hyperelliptic curves in characteristic p>2 for which the Hasse-Witt matrix is the zero matrix. For such curves, we establish an upper bound on the genus g, namely g≤(p-1)/2. For g=(p-1)/2, we establish the fact that up to isomorphism, there is precisely one such curve, namely the one given by the equation y2=xp-x. We determine all hyeprelliptic curves of the form y2=xn-x or y2=xn-1 for which the Hasse-Witt matrix is the zero matrix.
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Valentini, R.C. Hyperelliptic curves with zero Hasse-Witt matrix. Manuscripta Math 86, 185–194 (1995). https://doi.org/10.1007/BF02567987
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DOI: https://doi.org/10.1007/BF02567987