We give a deepened version of a lemma of Gabrielov and then use it to prove the following fact: if h ∈ 𝕂[[X]] (𝕂 = ℝ or ℂ) is a root of a non-zero polynomial with convergent power series coefficients, then h is convergent.
Some results and problems that arise in connection with the foundations of the theory of ruled and rational field extensions are discussed.
Let be a commutative ring, an -module and a group of -automorphisms of , usually with some sort of rank restriction on . We study the transfer of hypotheses between and such as Noetherian or having finite composition length. In this we extend recent work of Dixon, Kurdachenko and Otal and of Kurdachenko, Subbotin and Chupordia. For example, suppose is -Noetherian. If has finite rank, then also is -Noetherian. Further, if is -Noetherian and if only certain abelian sections...
We consider two issues concerning polynomial cycles. Namely, for a discrete valuation domain of positive characteristic (for ) or for any Dedekind domain of positive characteristic (but only for ), we give a closed formula for a set of all possible cycle-lengths for polynomial mappings in . Then we give a new property of sets , which refutes a kind of conjecture posed by W. Narkiewicz.
Let R be a real closed field, and denote by the ring of germs, at the origin of Rⁿ, of functions in a neighborhood of 0 ∈ Rⁿ. For each n ∈ ℕ, we construct a quasianalytic subring with some natural properties. We prove that, for each n ∈ ℕ, is a noetherian ring and if R = ℝ (the field of real numbers), then , 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 .
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;...