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On some issues concerning polynomial cycles

Tadeusz Pezda (2013)

Communications in Mathematics

We consider two issues concerning polynomial cycles. Namely, for a discrete valuation domain R of positive characteristic (for N 1 ) or for any Dedekind domain R of positive characteristic (but only for N 2 ), we give a closed formula for a set 𝒞 Y C L ( R , N ) of all possible cycle-lengths for polynomial mappings in R N . Then we give a new property of sets 𝒞 Y C L ( R , 1 ) , which refutes a kind of conjecture posed by W. Narkiewicz.

On some noetherian rings of C germs on a real closed field

Abdelhafed Elkhadiri (2011)

Annales Polonici Mathematici

Let R be a real closed field, and denote by R , n the ring of germs, at the origin of Rⁿ, of C functions in a neighborhood of 0 ∈ Rⁿ. For each n ∈ ℕ, we construct a quasianalytic subring R , n R , n with some natural properties. We prove that, for each n ∈ ℕ, R , n is a noetherian ring and if R = ℝ (the field of real numbers), then , n = , where ₙ is the ring of germs, at the origin of ℝⁿ, of real analytic functions. Finally, we prove the Real Nullstellensatz and solve Hilbert’s 17th Problem for the ring R , n .

On some properties of partial intersection schemes.

Alfio Ragusa, Giuseppe Zappalà (2003)

Collectanea Mathematica

Partial intersection subschemes of Pr of codimension c were used to furnish various graded Betti numbers which agree with a fixed Hilbert function. Here we study some further properties of such schemes; in particular, we show that they are not in general licci and we give a large class of them which are licci. Moreover, we show that all partial intersections are glicci. We also show that for partial intersections the first and the last Betti numbers, say m and p respectively, give bounds each other;...

On Strong Going-Between, Going-Down, And Their Universalizations, II

David E. Dobbs, Gabriel Picavet (2003)

Annales mathématiques Blaise Pascal

We consider analogies between the logically independent properties of strong going-between (SGB) and going-down (GD), as well as analogies between the universalizations of these properties. Transfer results are obtained for the (universally) SGB property relative to pullbacks and Nagata ring constructions. It is shown that if A B are domains such that A is an LFD universally going-down domain and B is algebraic over A , then the inclusion map A [ X 1 , , X n ] B [ X 1 , , X n ] satisfies GB for each n 0 . However, for any nonzero ring...

On strongly affine extensions of commutative rings

Nabil Zeidi (2020)

Czechoslovak Mathematical Journal

A ring extension R S is said to be strongly affine if each R -subalgebra of S is a finite-type R -algebra. In this paper, several characterizations of strongly affine extensions are given. For instance, we establish that if R is a quasi-local ring of finite dimension, then R S is integrally closed and strongly affine if and only if R S is a Prüfer extension (i.e. ( R , S ) is a normal pair). As a consequence, the equivalence of strongly affine extensions, quasi-Prüfer extensions and INC-pairs is shown. Let G be...

On symmetric semialgebraic sets and orbit spaces

Ludwig Bröcker (1998)

Banach Center Publications

For a symmetric (= invariant under the action of a compact Lie group G) semialgebraic basic set C, described by s polynomial inequalities, we show, that C can also be written by s + 1 G-invariant polynomials. We also describe orbit spaces for the action of G by a number of inequalities only depending on the structure of G.

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