The Quarterly Journal of Mathematics Advance Access published online on January 7, 2009
The Quarterly Journal of Mathematics, doi:10.1093/qmath/han035
CONSTRUCTION OF CLASS FIELDS OVER IMAGINARY QUADRATIC FIELDS AND APPLICATIONS


Department of Mathematical Sciences, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea
Corresponding author. E-mail: jkkoo{at}math.kaist.ac.kr
Received 18 July 2008;
revised 13 November 2008
| Abstract |
|---|
Let K be an imaginary quadratic field, H
the ring class field of an order
in K and K(N) be the ray class field modulo N over K for a positive integer N. In this paper we provide certain general techniques of finding H
and K(N) by using the theory of Shimura's canonical models via his reciprocity law, from which we partially extend some results of Schertz (Remark 4.2), Chen-Yui (Remark 4.2, Corollary 4.4), Cox–McKay–Stevenhagen (Corollary 4.5) and Cais–Conrad (Remark 5.3). And, we further reilluminate the classical result of Hasse by means of such a method (Corollary 5.4), and discover how to get one ray class invariant over K from Hasse's two generators (Corollary 5.5) which is different from Ramachandra's invariant [K. Ramachandra, Some applications of Kronecker's limit formulas, Ann. Math. 80 (1964), 104–148].
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