Atkin and Swinnerton‐Dyer Congruences and Noncongruence Modular Forms
RIMS Kôkyûroku Bessatsu B51 (2014), 269−299 Atkin and Swinnerton‐Dyer congruences and noncongruence modular forms By ** Wen‐Ching Winnie \mathrm{L}1^{*} and Ling LONG Abstract Atkin and Swinnerton‐Dyer congruences are special congruence recursions satised by coefficients of noncongruence modular forms. These are in some sense p‐adic analogues of Hecke recursion satised by classic Hecke eigenforms. They actually appeared in different contexts and sometimes can be obtained using the theory of formal groups. In this survey paper, we introduce the Atkin and Swinnerton‐Dyer congruences, and discuss some recent progress on this topic. §1. Introduction Atkin and Swinnerton‐Dyer (ASD) congruences in the title refer to the congruences of the form (1.1) a_{np}-A_{p}a_{n}+$\mu$_{p}p^{k-1}a_{n/p}\equiv 0 \mathrm{m}\mathrm{o}\mathrm{d} p^{(k-1)(1+\mathrm{o}rd_{p}n)} for all \mathrm{n}\geq 1, where p is a prime, a_{n} are integral over \mathbb{Z}_{p}, A_{p} is an algebraic integer, and $\mu$_{p} is a root of unity. The congruence means that the left hand side divided by the modulus is integral over \mathbb{Z}_{p} . As usual, a_{x}=0 if x is not an integer. The original purpose was to study Received March 24, 2013. Revised September 30, 2013, October 7, 2013, November 14, 2013, December 6, 2013, December 16, 2013 and February 6, 2014. 2010 Mathematics Subject Classication(s): 11\mathrm{F}11, 11\mathrm{F}33, 33\mathrm{C}20 The first author is supported by the NSF grant DMS‐1101368.
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