Part I gives algebraic basic notions necessary to generating a graded sheaf of rings from a Galois extension, i.e. essentially a specialization, called emergent, from a ring of polynomials A[x1, ..., xm] giving rise to a set of compact connected algebraic subgroups which correspond to the different sections of the sheaf of rings θ. Part II refers to the introduction of the Eisenstein homology b...

Let k be a field, Ln = k[x ±1 1 , . . . , x ±1 n ] be the Laurent polynomial ring in n variables and G be a group of k-algebra automorphisms of Ln. We give a necessary and sufficient condition for the ring of invariants Ln to have a SAGBI basis. We show that if this condition is satisfied then Ln has a SAGBI basis relative to any choice of coordinates in Ln and any term order.

Let R be a real closed field and A = R[x1, . . . , xn]. Let Sper A denote the real spectrum of A. There are two kinds of points in Sper A: finite points (those for which all of |x1|,. . . ,|xn| are bounded above by some constant in R) and points at infinity. In this paper we study the structure of the set of points at infinity of Sper A and their associated valuations. Let T be a subset of {1, ...

The rank rk(R) of a ring R is the supremum of minimal cardinalities of generating sets of I as I ranges over ideals of R. Matson showed that every n ∈ Z+ occurs as the rank of some ring R. Motivated by the result of Cohen and Gilmer that a ring of finite rank has Krull dimension 0 or 1, we give four different constructions of rings of rank n (for all n ∈ Z+). Two constructions use one-dimension...

Motivated by recent results on the Waring problem for polynomial rings [FOS12] and representation of monomial as sum of powers of linear forms [CCG12], we consider the problem of presenting monomials of degree kd as sums of kth-powers of forms of degree d. We produce a general bound on the number of summands for any number of variables which we refine in the two variables case. We completely so...

We classify all simple transitive 2-representations for two classes of finitary 2-categories associated with tree path algebras and also for one class of fiat 2-categories associated with truncated polynomial rings. Additionally, we compute the Drinfeld centers for all these 2-categories.

Linear operators preserving the direct sum of polynomial rings P(m)⊕P(n) are constructed. In the case |m − n| = 1 they correspond to atypical representations of the superalgebra osp(2,2). For |m − n| = 2 the generic, finite dimensional representations of the superalgebra q(2) are recovered. Examples of Hamiltonians possessing such a hidden algebra are analyzed. PACS numbers: 02.20.Sv, 03.65.Fd ...

The paper proposes a new construction for studying various properties of a polynomial with respect to an ideal generated by a finite basis of polynomials. These properties include, among others, (i) checking whether the polynomial is a zero divisor in the residue class ring defined by the associated ideal and (ii) checking whether the polynomial is invertible in the residue class ring defined b...

LetW be a finite dimensional representation of a linearly reductive group G over a field k. Motivated by their work on classical rings of invariants, Levasseur and Stafford asked whether the ring of invariants under G of the symmetric algebra of W has a simple ring of differential operators. In this paper, we show that this is true in prime characteristic. Indeed, if R is a graded subring of a ...

Let k be a real field. We show that every non-negative homogeneous quadratic polynomial f(x1, . . . , xn) with coefficients in the polynomial ring k[t] is a sum of 2n · τ(k) squares of linear forms, where τ(k) is the supremum of the levels of the finite non-real field extensions of k. From this result we deduce bounds for the Pythagoras numbers of affine curves over fields, and of excellent two...