Divisibility of class numbers of imaginary quadratic function fields by a fixed odd number |
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Authors: | PRADIPTO BANERJEE SRINIVAS KOTYADA |
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Affiliation: | 1. Indian Statistical Institute, Stat-Math Unit, 203 Barrackpore Trunk Road, Kolkata, 700 108, India 2. Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai, 600 113, India
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Abstract: | In this paper we find a new lower bound on the number of imaginary quadratic extensions of the function field $mathbb{F}_{q}(x)$ 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 $gg q^{L(frac{1}{2}+frac{3}{2(g+1)}-epsilon)}$ polynomials $f in mathbb{F}_{q}[x]$ with $deg f=L$ , for which the class group of the quadratic extension $mathbb{F}_{q}(x, sqrt{f})$ has an element of order g. This sharpens the previous lower bound $q^{L(frac{1}{2}+frac{1}{g})}$ 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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