Divisibility of class numbers of imaginary quadratic function fields by a fixed odd number

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作者
PRADIPTO BANERJEE
SRINIVAS KOTYADA
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[1] Indian Statistical Institute,Institute of Mathematical Sciences
[2] Stat-Math Unit,undefined
[3] CIT Campus,undefined
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Divisibility; class numbers; quadratic extensions; function fields;
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摘要
In this paper we find a new lower bound on the number of imaginary quadratic extensions of the function field \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mathbb{F}_{q}(x)$\end{document} whose class groups have elements of a fixed odd order. More precisely, for q, a power of an odd prime, and g a fixed odd positive integer ≥ 3, we show that for every ε > 0, there are \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\gg q^{L(\frac{1}{2}+\frac{3}{2(g+1)}-\epsilon)}$\end{document} polynomials \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$f \in \mathbb{F}_{q}[x]$\end{document} with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\deg f=L$\end{document}, for which the class group of the quadratic extension \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\mathbb{F}_{q}(x, \sqrt{f})$\end{document} has an element of order g. This sharpens the previous lower bound \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$q^{L(\frac{1}{2}+\frac{1}{g})}$\end{document} of Ram Murty. Our result is a function field analogue which is similar to a result of Soundararajan for number fields.
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页码:1 / 18
页数:17
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