EuDML | Browse

In this paper we study big convexity theories, that is convexity theories that are not necessarily bounded. As in the bounded case (see [4]) such a convexity theory Γ gives rise to the category ΓC of (left) Γ-convex modules. This is an equationally presentable category, and we prove that it is indeed an algebraic category over Set. We also introduce the category ΓAlg of Γ-convex algebras and show that the category Frm of frames is isomorphic to the category of associative, commutative, idempotent...

Coordinates of maximal roots of weakly non-negative unit forms

P. Dräxler, N. Golovachtchuk, S. Ovsienko, J. de la Pena (1998)

Colloquium Mathematicae

Copure injective resolutions, flat resolvents and dimensions

Edgar E. Enochs, Jenda M. G. Overtoun (1993)

Commentationes Mathematicae Universitatis Carolinae

In this paper, we show the existence of copure injective preenvelopes over noetherian rings and copure flat preenvelopes over commutative artinian rings. We use this to characterize $n$ -Gorenstein rings. As a consequence, if the full subcategory of strongly copure injective (respectively flat) modules over a left and right noetherian ring $R$ has cokernels (respectively kernels), then $R$ is $2$ -Gorenstein.

Corestriction of central simple algebras and families of Mumford-type

Federica Galluzzi (1999)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

Let $M$ be a family of Mumford-type, that is, a family of polarized complex abelian fourfolds as introduced by Mumford in [9]. This family is defined starting from a quaternion algebra $A$ over a real cubic number field and imposing a condition to the corestriction of such $A$ . In this paper, under some extra conditions on the algebra $A$ , we make this condition explicit and in this way we are able to describe the polarization and the complex structures of the fibers. Then, we look at the non simple $C M$ -fibers...