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On the torsion of Drinfeld modules of rank two

Published/Copyright: January 20, 2010
Journal für die reine und angewandte Mathematik
From the journal Volume 2010 Issue 640

Abstract

We prove that the curve Y0(𝔭) has no 𝔽2(T)-rational points where 𝔭 ⊲ 𝔽2[T] is a prime ideal of degree at least 3 and Y0(𝔭) is the affine Drinfeld modular curve parameterizing Drinfeld modules of rank two over 𝔽2[T] of generic characteristic with Hecke-type level 𝔭-structure. As a consequence we derive a conjecture of Schweizer describing completely the torsion of Drinfeld modules of rank two over 𝔽2(T) implying the uniform boundedness conjecture in this particular case. We reach our results with a variant of the formal immersion method. Moreover we show that the group Aut(X0(𝔭)) has order two. As a further application of our methods we also determine the prime-to-p cuspidal torsion packet of X0(𝔭) where 𝔭 ⊲ 𝔽q[T] is a prime ideal of degree at least 3 and q is a power of the prime p.

Received: 2007-09-04
Revised: 2008-09-24
Published Online: 2010-01-20
Published in Print: 2010-March

© Walter de Gruyter Berlin · New York 2010

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