Primitive representation of a binary quadratic form as a sum of four squares
In this paper we consider proper cycles of indefinite integral quadratic forms with discriminant . We prove that the proper cycles of can be obtained using their consecutive right neighbors for . We also derive explicit relations in the cycle and proper cycle of when the length of the cycle of is odd, using the transformations and .
Let be a field of characteristic . Let be a over (i.e., an -truncated Barsotti–Tate group over ). Let be a -scheme and let be a over . Let be the subscheme of which describes the locus where is locally for the fppf topology isomorphic to . If , we show that is pure in , i.e. the immersion is affine. For , we prove purity if satisfies a certain technical property depending only on its -torsion . For , we apply the developed techniques to show that all level ...