RELATIVE EXACTNESS MODULO A POLYNOMIAL MAP AND ALGEBRAIC ( C p , + ) - ACTIONS
نویسنده
چکیده
— Let F = (f1, . . . , fq) be a polynomial dominating map from Cn to Cq. We study the quotient T 1(F ) of polynomial 1-forms that are exact along the generic fibres of F , by 1-forms of type dR+ ∑ aidfi, where R, a1, . . . , aq are polynomials. We prove that T 1(F ) is always a torsion C[t1, . . . , tq ]-module. Then we determine under which conditions on F we have T 1(F ) = 0. As an application, we study the behaviour of a class of algebraic (Cp,+)-actions on Cn, and determine in particular when these actions are trivial. Résumé (Exactitude relative modulo une application polynomiale et actions algébriques de (Cp,+)) Soit F = (f1, . . . , fq) une application polynomiale dominante de Cn dans Cq. Nous étudions le quotient T 1(F ) des 1-formes polynomiales qui sont exactes le long des fibres génériques de F , par les 1-formes du type dR + ∑ aidfi, où R, a1, . . . , aq sont des polynômes. Nous montrons que T 1(F ) est toujours un C[t1, . . . , tq]-module de torsion. Nous déterminons ensuite sous quelles conditions sur F ce module est réduit à zéro. En application, nous étudions le comportement d’une classe d’actions algébriques de (Cp,+) sur Cn, et nous déterminons en particulier quand ces actions sont triviales.
منابع مشابه
Fe b 20 06 Relative exactness modulo a polynomial map and algebraic ( C p , + ) - actions Philippe Bonnet 2 nd February 2008
Relative exactness modulo a polynomial map and algebraic (C p , +)-actions Abstract Let F = (f 1 , .., f q) be a polynomial dominating map from C n to C q. In this paper we study the quotient T 1 (F) of polynomial 1-forms that are exact along the generic fibres of F , by 1-forms of type dR + a i df i , where R, a 1 , .., a q are polynomials. We prove that T 1 (F) is always a torsion C[t 1 , ......
متن کاملAdelic constructions for direct images of differentials and symbols
Let X be a smooth algebraic surface over a perfect field k. Consider pairs x ∈ C , x is a closed point of X , C is either an irreducible curve on X which is smooth at x, or an irreducible analytic branch near x of an irreducible curve on X . As in the previous section 1 for every such pair x ∈ C we get a two-dimensional local field Kx,C . If X is a projective surface, then from the adelic descr...
متن کاملSurjectivity of quotient maps for algebraic (C,+)-actions and polynomial maps with contractible fibres
In this paper, we establish two results concerning algebraic (C,+)-actions on C. First of all, let φ be an algebraic (C,+)-action on C3. By a result of Miyanishi, its ring of invariants is isomorphic to C[t1, t2]. If f1, f2 generate this ring, the quotient map of φ is the map F : C3 → C2, x 7→ (f1(x), f2(x)). By using some topological arguments, we prove that F is always surjective. Secondly we...
متن کاملRecovering an Algebraic Curve Using its Projections From Different Points Applications to Static and Dynamic Computational Vision
We study how an irreducible closed algebraic curve X embedded in CP , which degree is d and genus g, can be recovered using its projections from points onto embedded projective planes. The different embeddings are unknown. The only input is the defining equation of each projected curve. We show how both the embeddings and the curve in CP can be recovered modulo some actions of the group of proj...
متن کاملAn Efficient Algorithm for Factoring Polynomials over Algebraic Extension Field
An efficient algorithm is presented for factoring polynomials over an algebraic extension field. The extension field is defined by a polynomial ring modulo a maximal ideal. If the ideal is given by its Gröbner basis, no extra Gröbner basis computation is needed for factoring a polynomial over the extension field. We will only use linear algebra to get a polynomial over the base field by a gener...
متن کامل