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| | Isomorphisms and Transformations |
 | | A hyperelliptic curve isomorphism curve defined by the data of a linear fractional transformation t(x:z) = (ax + bz:cx + dz), a scale factor e, and a polynomial u(x) of degree at most g + 1, where g is the genus of the curve. |
 | | An isomorphism can be created from the parent structures by coercing a tuple < [a, b, c, d], e, u > into the structure of isomorphisms between two hyperelliptic curves, or by creating it as a transformation of a given curve, i.e. |
 | | So in the former case the automorphism group is an extension of the elliptic curve automorphism group (of order 2) by Z/2Z, and in latter case the automorphism group is an extension (of the group of order 12) by the abelian group isomorphic to Z/2Z x Z/2Z. |
| www.umich.edu /~gpcc/scs/magma/text1076.htm (1190 words) |
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