On modules in which idempotent reducts form a chain
A ring extension is said to be FO if it has only finitely many intermediate rings. is said to be FC if each chain of distinct intermediate rings in this extension is finite. We establish several necessary and sufficient conditions for the ring extension to be FO or FC together with several other finiteness conditions on the set of intermediate rings. As a corollary we show that each integrally closed ring extension with finite length chains of intermediate rings is necessarily a normal pair...
Soit le localisé de l’anneau des polynômes à trois variables sur le corps de caractéristique nulle. Nous construisons une valuation divisorielle de , nous calculons un système minimal de générateurs de la -algèbre associée à la filtration -adique. Ce système est infini : n’est pas noethérien.