Integral quadratic forms and Dirichlet series
 B. van Asch,
 F. van der Blij
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Abstract
A Dirichlet series with multiplicative coefficients has an Euler product representation. In this paper we consider the special case where these coefficients are derived from the numbers of representations of an integer by an integral quadratic form. At first we suppose this quadratic form to be positive definite. In general the representation numbers are not multiplicative. Instead we consider the average number of representations over all classes in the genus of the quadratic form. And we consider only representations of integers of the form tk ^{2} with t squarefree. If we divide the average representation number for these integers by a suitable factor, we do get a multiplicative function. Using results from Siegel (Ann. Math. 36:527–606, 1935), we derive a uniform expression for the Euler product expansion of the corresponding Dirichlet series. As a special case, we consider the standard quadratic form in n variables corresponding to the identity matrix. Here we use results from Shimura (Am. J. Math. 124:1059–1081, 2002). For 2≤n≤8, the genus of this particular quadratic form contains only one class, and this leads to a rather simple expression for the Dirichlet series, where the coefficients are just the number of representations of a square as the sum of n squares. Finally we consider the indefinite case, where we can get results similar to the definite case.
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 Title
 Integral quadratic forms and Dirichlet series
 Open Access
 Available under Open Access This content is freely available online to anyone, anywhere at any time.
 Journal

The Ramanujan Journal
Volume 22, Issue 1 , pp 110
 Cover Date
 20100501
 DOI
 10.1007/s1113900992176
 Print ISSN
 13824090
 Online ISSN
 15729303
 Publisher
 Springer US
 Additional Links
 Topics
 Keywords

 Integral quadratic form
 Multiplicative function
 Dirichlet series
 Euler product
 11B34
 11E25
 11F66
 11K65
 Authors

 B. van Asch ^{(1)}
 F. van der Blij ^{(1)}
 Author Affiliations

 1. Department of Mathematics and Computing Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands