Monatshefte für Mathematik

, Volume 143, Issue 2, pp 163-167

First online:

A Short Remark on Weierstrass Points at Infinity on X 0(N)

  • Winfried KohnenAffiliated withUniversität Heidelberg

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We point out that the formalism of the trace map and reduction modulo p can be used to give a short proof for the fact first proved by Ogg that ∞ is not a Weierstrass point on X 0(pM) where p is a prime not dividing M and the genus of X 0(M) is zero.

2000 Mathematics Subject Classification: 11F, 11G
Key words: Weierstrass point, modular curve, modular form