scholarly journals The automorphism group of a function field

1992 ◽  
Vol 115 (4) ◽  
pp. 923-923 ◽  
Author(s):  
Manohar Madan ◽  
Michael Rosen
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nurdagül Anbar ◽  
Burçin Güneş

Abstract We study the automorphisms of a function field of genus g ≥ 2 over an algebraically closed field of characteristic p > 0. More precisely, we show that the order of a nilpotent subgroup G of its automorphism group is bounded by 16 (g – 1) when G is not a p-group. We show that if |G| = 16(g – 1), then g – 1 is a power of 2. Furthermore, we provide an infinite family of function fields attaining the bound.


Author(s):  
Urs Hartl ◽  
Eva Viehmann

Abstract Moduli spaces of bounded local G-shtukas are a group-theoretic generalisation of the function field analogue of Rapoport and Zink’s moduli spaces of p-divisible groups. In this article we generalise some very prominent concepts in the theory of Rapoport-Zink spaces to our setting. More precisely, we define period spaces, as well as the period map from a moduli space of bounded local G-shtukas to the corresponding period space, and we determine the image of the period map. Furthermore, we define a tower of coverings of the generic fibre of the moduli space, which is equipped with a Hecke action and an action of a suitable automorphism group. Finally, we consider the $\ell $ -adic cohomology of these towers. Les espaces de modules de G-chtoucas locaux bornés sont une généralisation des espaces de modules de groupes p-divisibles de Rapoport-Zink, au cas d’un corps de fonctions local, pour des groupes plus généraux et des copoids pas nécessairement minuscules. Dans cet article nous définissons les espaces de périodes et l’application de périodes associés à un tel espace, et nous calculons son image. Nous étudions la tour au-dessus de la fibre générique de l’espace de modules, équipée d’une action de Hecke ainsi que d’une action d’un groupe d’automorphismes. Enfin, nous définissons la cohomologie $\ell $ -adique de ces tours.


2013 ◽  
Vol 13 (2) ◽  
Author(s):  
Cem Güneri ◽  
Mehmet Özdemiry ◽  
Henning Stichtenoth

2004 ◽  
Vol 03 (01) ◽  
pp. 75-89 ◽  
Author(s):  
TANUSH SHASKA

Let [Formula: see text] denote the locus of hyperelliptic curves of genus g whose automorphism group contains a subgroup isomorphic to G. We study spaces [Formula: see text] for G≅ℤn, ℤ2⊕ℤn, ℤ2⊕A4, or SL2(3). We show that for G≅ℤn, ℤ2⊕ℤn, the space [Formula: see text] is a rational variety and find generators of its function field. For G≅ℤ2⊕A4, SL2(3) we find a necessary condition in terms of the coefficients, whether or not the curve belongs to [Formula: see text]. Further, we describe algebraically the loci of such curves for g≤12 and show that for all curves in these loci, the field of moduli is a field of definition.


2019 ◽  
Vol 31 (1) ◽  
pp. 265-273
Author(s):  
Fabio Podestà ◽  
Alberto Raffero

Abstract We prove that the automorphism group of a compact 6-manifold M endowed with a symplectic half-flat {\mathrm{SU}(3)} -structure has Abelian Lie algebra with dimension bounded by {\min\{5,b_{1}(M)\}} . Moreover, we study the properties of the automorphism group action and we discuss relevant examples. In particular, we provide new complete examples on {T\mathbb{S}^{3}} which are invariant under a cohomogeneity one action of {\mathrm{SO}(4)} .


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