Copyright © The Author 2007. Published by Oxford University Press.
Reflection Principles and Bounds for Class Group Torsion
1 Department of Mathematics, University of Wisconsin, Madison
2 Courant Institute of Mathematical Sciences, New York University, New York
Correspondence: Correspondence to be sent to: Akshay Venkatesh, Courant Institute of Mathematical Sciences, New York University, New York. e-mail: akshay.venkatesh{at}gmail.com
We introduce a new method to bound
-torsion in class groups, combining analytic ideas with reflection principles. This gives, in particular, new bounds for the 3-torsion part of class groups in quadratic, cubic and quartic number fields, as well as bounds for certain families of higher degree fields and for higher
. Conditionally on GRH, we obtain a nontrivial bound for
-torsion in the class group of a general number field.