Let f1, . . . , fs be formal power series (respectively polynomials) in the variable x. We study the semigroup of orders of the formal series in the algebra KJf1, . . . , fsK ⊆ KJxK (respectively the semigroup of degrees of polynomials in K[f1, . . . , fs] ⊆ K[x]). We give procedures to compute these semigroups and several applications. We prove in particular that the space curve parametrized b...

We construct a Hopf algebra structure on the space of specified Feynman graphs of a quantum field theory. We introduce a convolution product and a semigroup of characters of this Hopf algebra with values in some suitable commutative algebra taking momenta into account. We then implement the renormalization described by A. Connes and D. Kreimer in [2] and the Birkhoff decomposition for two renor...

We consider a free action of an Ore semigroup on a higher-rank graph, and the induced action by endomorphisms of the C ∗-algebra of the graph. We show that the crossed product by this action is stably isomorphic to the C ∗-algebra of a quotient graph. Our main tool is Laca’s dilation theory for endomorphic actions of Ore semigroups on C ∗-algebras, which embeds such an action in an automorphic ...

This paper is devoted to the algebraic and combinatorial properties of polytopal semigroup rings defined as follows. Let P be a lattice polytope in R n , i. e. a poly-tope whose vertices have integral coordinates, and K a field. Then one considers the embedding ι : R n → R n+1 , ι(x) = (x, 1), and defines S P to be the semigroup generated by the lattice points in ι(P); the K-algebra K[S P ] is ...

This paper describes algorithms for computing the structure of finite transformation semigroups. The algorithms depend crucially on a new data structure for an R-class in terms of a group and an action. They provide for local computations, concerning a single R-class, without computing the whole semigroup, as well as for computing the global structure of the semigroup. The algorithms have been ...

Let $R$ be a positively graded algebra over field. We say that is Hilbert-cyclotomic if the numerator of its reduced Hilbert series has all roots on unit circle. Such rings arise naturally in commutative algebra, numerical semigroup theory and Ehrhart theory. If standard graded, we prove that, under additional hypothesis Koszul or an irreducible $h$-polynomial, algebras coincide with complete i...

lthough fuzzy set theory and  sheaf theory have been developed and studied independently,  Ulrich Hohle shows that a large part of fuzzy set  theory  is in fact a subfield of sheaf theory. Many authors have studied mathematical structures, in particular, algebraic structures, in both  categories of these generalized (multi)sets. Using Hohle's idea, we show that for a (universal) algebra $A$, th...