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Harmonic and equianharmonic equations in the Grothendieck–Teichmüller group. III

Published online by Cambridge University Press:  11 August 2009

Hiroaki Nakamura
Affiliation:
Department of Mathematics, Faculty of Science, Okayama University, Okayama 700-8530, Japan (h-naka@math.okayama-u.ac.jp)
Hiroshi Tsunogai
Affiliation:
Department of Mathematics, Sophia University, Tokyo 102-8554, Japan (tsuno-h@cc.sophia.ac.jp)
Seidai Yasuda
Affiliation:
Research Institute of Mathematical Science, Kyoto University, Kyoto 606-8502, Japan (yasuda@kurims.kyoto-u.ac.jp)

Abstract

We study behaviours of the ‘equianharmonic’ parameter of the Grothendieck–Teichmüller group introduced by Lochak and Schneps. Using geometric construction of a certain one-parameter family of quartics, we realize the Galois action on the fundamental group of a punctured Mordell elliptic curve in the standard Galois action on a specific subgroup of the braid group . A consequence is to represent a matrix specialization of the ‘equianharmonic’ parameter in terms of special values of the adelic beta function introduced and studied by Anderson and Ihara.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2010

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