La théorie des valuations née des travaux des géomètres et arithméticiens du XIX${}^{ê\mathrm{me}}$ siècle, fit une apparition tardive et encore peu connue au XX${}^{ê\mathrm{me}}$ siècle en algèbre différentielle. Dans cet article, à travers les contributions de nombreux auteurs, nous présentons une synthèse des divers apports de la théorie des valuations à l’étude des équations différentielles. Nous insistons sur le caractère unificateur de la théorie des valuations en illustrant comment elles permettent de mettre en parallèle des...

Let be M a smooth manifold, A a local algebra and $M^A$ a manifold of infinitely near points on M of kind A. We build the canonical foliation on $M^A$ and we show that the canonical foliation on the tangent bundle TM is the foliation defined by its canonical field.

Frobenius modules are difference modules with respect to a Frobenius operator. Here we show that over non-archimedean complete differential fields Frobenius modules define differential modules with the same Picard-Vessiot ring and the same Galois group schemes up to extension by constants. Moreover, these Frobenius modules are classified by unramified Galois representations over the base field. This leads among others to the solution of the inverse differential Galois problem for $p$-adic differential...

Let $k$ be a commutative ring, $A$ a commutative $k$-algebra and $D$ the filtered ring of $k$-linear differential operators of $A$. We prove that: (1) The graded ring $\mathrm{gr}\mathrm{D}$ admits a canonical embedding $\theta$ into the graded dual of the symmetric algebra of the module ${\Omega }_{A/k}$ of differentials of $A$ over $k$, which has a canonical divided power structure. (2) There is a canonical morphism $\vartheta$ from the divided power algebra of the module of $k$-linear Hasse–Schmidt integrable derivations of $A$ to $\mathrm{gr}\mathrm{D}$. (3) Morphisms $\theta$ and $\vartheta$ fit into a...

We study the LND conjecture concerning the images of locally nilpotent derivations, which arose from the Jacobian conjecture. Let $R$ be a domain containing a field of characteristic zero. We prove that, when $R$ is a one-dimensional unique factorization domain, the image of any locally nilpotent $R$-derivation of the bivariate polynomial algebra $R[x,y]$ is a Mathieu-Zhao subspace. Moreover, we prove that, when $R$ is a Dedekind domain, the image of a locally nilpotent $R$-derivation of $R[x,y]$ with some additional conditions...

We prove that an irreducible polynomial derivation in positive characteristic is a Jacobian derivation if and only if there exists an (n-1)-element p-basis of its ring of constants. In the case of two variables we characterize these derivations in terms of their divergence and some nontrivial constants.

Let k be a field. We describe all linear derivations d of the polynomial algebra k[x₁,...,xₘ] such that the algebra of constants with respect to d is generated by linear forms: (a) over k in the case of char k = 0, (b) over $k[x{₁}^p,...,x{ₘ}^p]$ in the case of char k = p > 0.

We give a description of all local derivations (in the Kadison sense) in the polynomial ring in one variable in characteristic two. Moreover, we describe all local derivations in the power series ring in one variable in any characteristic.

We give a new proof of Miyanishi's theorem on the classification of the additive group scheme actions on the affine plane.

We prove that every locally nilpotent monomial k-derivation of k[X₁,...,Xₙ] is triangular, whenever k is a ring of characteristic zero. A method of testing monomial k-derivations for local nilpotency is also presented.

Let $P$ be a poset and $d$ be a derivation on $P$. In this research, the notion of generalized $d$-derivation on partially ordered sets is presented and studied. Several characterization theorems on generalized $d$-derivations are introduced. The properties of the fixed points based on the generalized $d$-derivations are examined. The properties of ideals and operations related with generalized $d$-derivations are studied.

Let k be a field. We prove that any polynomial ring over k is a Kadison algebra if and only if k is infinite. Moreover, we present some new examples of Kadison algebras and examples of algebras which are not Kadison algebras.

Let k be a field of chracteristic p > 0. We describe all derivations of the polynomial algebra k[x,y], homogeneous with respect to a given weight vector, in particular all monomial derivations, with the ring of constants of the form $k[x^p,y^p,f]$, where $f\in k[x,y]\setminus k[x^p,y^p]$.

Let d be a k-derivation of k[x,y], where k is a field of characteristic zero. Denote by $\tilde{d}$ the unique extension of d to k(x,y). We prove that if ker d ≠ k, then ker $\tilde{d}$ = (ker d)0, where (ker d)0 is the field of fractions of ker d.

We show that the GVC (generalized vanishing conjecture) holds for the differential operator $\Lambda =({\partial }_x-\Phi \left({\partial }_y\right)){\partial }_y$ and all polynomials $P(x,y)$, where $\Phi \left(t\right)$ is any polynomial over the base field. The GVC arose from the study of the Jacobian conjecture.

Let k[[x,y]] be the formal power series ring in two variables over a field k of characteristic zero and let d be a nonzero derivation of k[[x,y]]. We prove that if Ker(d) ≠ k then Ker(d) = Ker(δ), where δ is a jacobian derivation of k[[x,y]]. Moreover, Ker(d) is of the form k[[h]] for some h ∈ k[[x,y]].

We describe the ring of constants of a specific four variable Lotka-Volterra derivation. We investigate the existence of polynomial constants in the other cases of Lotka-Volterra derivations, also in n variables.