Abstract:Abstract. We show that over a field of characteristic 2 a central simple algebra with orthogonal involution that decomposes into a product of quaternion algebras with involution is either anisotropic or metabolic. We use this to define an invariant of such orthogonal involutions in characteristic 2 that completely determines the isotropy behaviour of the involution. We also give an example of a non-totally decomposable algebra with orthogonal involution that becomes totally decomposable over every splitting fi… Show more
“…Now, let be a representative of the class , . By [, (7.3)], the bilinear Pfister form is independent of the decomposition of . As in , we denote this form by .…”
Section: Orthogonal Pfister Involutinsmentioning
confidence: 99%
“…Since an orthogonal involution in characteristic two cannot be hyperbolic, one may replace the hyperbolicity condition with metabolicity. Also, using [, (5.5)] one can find a metabolic bilinear form of dimension over a field which is not similar to any Pfister form. This can be used to show that the implication is not true in characteristic two.…”
Section: Introductionmentioning
confidence: 99%
“…However, by [, (5.5)] an anisotropic symmetric bilinear form of dimension over , which is either anisotropic or metabolic over all extensions of , is similar to a Pfister form. Considering this result a conjecture may be formulated as follows (see ): Conjecture Let be a central simple algebra of degree with orthogonal involution over a field of characteristic two. If is anisotropic, then the following statements are equivalent.…”
Section: Introductionmentioning
confidence: 99%
“…The implication follows from [, (6.2)] (even without the anisotropy condition on ). The implication was also proved in [, (8.3)]. The aim of this work is to prove the implication .…”
In characteristic two, it is shown that a central simple algebra of degree equal to a power of two with anisotropic orthogonal involution is totally decomposable, if it becomes either anisotropic or metabolic over all extensions of the ground field. A similar result is obtained for the case where this algebra with involution is Brauer-equivalent to a quaternion algebra and it becomes adjoint to a bilinear Pfister form over all splitting fields of the algebra.
“…Now, let be a representative of the class , . By [, (7.3)], the bilinear Pfister form is independent of the decomposition of . As in , we denote this form by .…”
Section: Orthogonal Pfister Involutinsmentioning
confidence: 99%
“…Since an orthogonal involution in characteristic two cannot be hyperbolic, one may replace the hyperbolicity condition with metabolicity. Also, using [, (5.5)] one can find a metabolic bilinear form of dimension over a field which is not similar to any Pfister form. This can be used to show that the implication is not true in characteristic two.…”
Section: Introductionmentioning
confidence: 99%
“…However, by [, (5.5)] an anisotropic symmetric bilinear form of dimension over , which is either anisotropic or metabolic over all extensions of , is similar to a Pfister form. Considering this result a conjecture may be formulated as follows (see ): Conjecture Let be a central simple algebra of degree with orthogonal involution over a field of characteristic two. If is anisotropic, then the following statements are equivalent.…”
Section: Introductionmentioning
confidence: 99%
“…The implication follows from [, (6.2)] (even without the anisotropy condition on ). The implication was also proved in [, (8.3)]. The aim of this work is to prove the implication .…”
In characteristic two, it is shown that a central simple algebra of degree equal to a power of two with anisotropic orthogonal involution is totally decomposable, if it becomes either anisotropic or metabolic over all extensions of the ground field. A similar result is obtained for the case where this algebra with involution is Brauer-equivalent to a quaternion algebra and it becomes adjoint to a bilinear Pfister form over all splitting fields of the algebra.
“…The converse, that any orthogonal involution on an algebra of two-power degree that is anisotropic or hyperbolic after extending scalars to any field extension is necessarily totally decomposable, is clear for split algebras, but otherwise remains largely open. In [7], this question is considered for orthogonal involutions in characteristic two, whose behaviour is somewhat unusual.…”
Abstract. We study totally decomposable symplectic and unitary involutions on central simple algebras of index 2 and on split central simple algebras respectively. We show that for every field extension, these involutions are either anisotropic or hyperbolic after extending scalars, and that the converse holds if the algebras are of 2-power degree. These results are new in characteristic 2, otherwise were shown in [3] and [6] respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.