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Skolem–Mahler–Lech type theorems and Picard–Vessiot theory

Michael Wibmer (2015)

Journal of the European Mathematical Society

We show that three problems involving linear difference equations with rational function coefficients are essentially equivalent. The first problem is the generalization of the classical Skolem–Mahler–Lech theorem to rational function coefficients. The second problem is whether or not for a given linear difference equation there exists a Picard–Vessiot extension inside the ring of sequences. The third problem is a certain special case of the dynamical Mordell–Lang conjecture. This allows us to deduce...

Slope filtration of quasi-unipotent overconvergent F -isocrystals

Nobuo Tsuzuki (1998)

Annales de l'institut Fourier

We study local properties of quasi-unipotent overconvergent F -isocrystals on a curve over a perfect field of positive characteristic p . For a φ - ∇ -module over the Robba ring ℛ , we define the slope filtration for Frobenius structures. We prove that an overconvergent F -isocrystal is quasi-unipotent if and only if it has the slope filtration for Frobenius structures locally at every point on the complement of the curve.

Specializations of one-parameter families of polynomials

Farshid Hajir, Siman Wong (2006)

Annales de l’institut Fourier

Let K be a number field, and suppose λ ( x , t ) ∈ K [ x , t ] is irreducible over K ( t ) . Using algebraic geometry and group theory, we describe conditions under which the K -exceptional set of λ , i.e. the set of α ∈ K for which the specialized polynomial λ ( x , α ) is K -reducible, is finite. We give three applications of the methods we develop. First, we show that for any fixed n ≥ 10 , all but finitely many K -specializations of the degree n generalized Laguerre polynomial L n ( t ) ( x ) are K -irreducible and have Galois group S n . Second, we study specializations...

Stokes phenomenon, multisummability and differential Galois groups

Michèle Loday-Richaud (1994)

Annales de l'institut Fourier

We precise the cohomological analysis of the Stokes phenomenon for linear differential systems due to Malgrange and Sibuya by making a rigid natural choice of a unique cocycle (called a Stokes cocyle) in every cohomological class. And we detail an algebraic algorithm to reduce any cocycle to its cohomologous Stokes form. This gives rise to an almost algebraic definition of sums for formal solutions of systems which we compare to the most usual ones. We also use this construction to the Stokes cocycle...

Sur certaines algèbres de Lie de dérivations

Yves Félix, Stephen Halperin, Jean-Claude Thomas (1982)

Annales de l'institut Fourier

Il est démontré que toute a.d.g.c. ayant un modèle minimal de Sullivan de type fini peut être représentée par une certaine algèbre de Lie différentielle graduée de dérivations. En particulier on peut ainsi représenter le type d’homotopie rationnelle d’un espace topologique.

Sur le Topos infinitésimal p -adique d’un schéma lisse I

Alberto Arabia, Zoghman Mebkhout (2010)

Annales de l’institut Fourier

Afin de disposer des opérations cohomologiques aussi souples que possible pour la cohomologie de de Rham p -adique, le but principal de ce mémoire est de résoudre intrinsèquement du point de vue cohomologique le problème des relèvements des schémas lisses et de leurs morphismes de la caractéristique p > 0 à la caractéristique nulle ce qui a été l’une des difficultés centrales de la théorie de la cohomologie de de Rham des schémas algébriques en caractéristique positive depuis le début. Nous montrons...

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