Displaying similar documents to “The fundamental group of a Galois cover of 1 × T .”

Characteres and Galois invariants of regular dessins.

Manfred Streit, Jürgen Wolfart (2000)

Revista Matemática Complutense

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We describe a new invariant for the action of the absolute Galois groups on the set of Grothendieck dessins. It uses the fact that the automorphism groups of regular dessins are isomorphic to automorphism groups of the corresponding Riemman surfaces and define linear represenatations of the space of holomorphic differentials. The characters of these representations give more precise information about the action of the Galois group than all previously known invariants, as it is shown...

Cubic surfaces with a Galois invariant double-six

Andreas-Stephan Elsenhans, Jörg Jahnel (2010)

Open Mathematics

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We present a method to construct non-singular cubic surfaces over ℚ with a Galois invariant double-six. We start with cubic surfaces in the hexahedral form of L. Cremona and Th. Reye. For these, we develop an explicit version of Galois descent.

The Lamé family of connections on the projective line

Frank Loray, Marius van der Put, Felix Ulmer (2008)

Annales de la faculté des sciences de Toulouse Mathématiques

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This paper deals with rank two connections on the projective line having four simple poles with prescribed local exponents 1/4 and - 1 / 4 . This Lamé family of connections has been extensively studied in the literature. The differential Galois group of a Lamé connection is never maximal : it is either dihedral (finite or infinite) or reducible. We provide an explicit moduli space of those connections having a free underlying vector bundle and compute the algebraic locus of those reducible...