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On some iterated means arising in homogenization theory

Dag Lukkassen, Jaak Peetre, Lars-Erik Persson (2004)

Applications of Mathematics

We consider iteration of arithmetic and power means and discuss methods for determining their limit. These means appear naturally in connection with some problems in homogenization theory.

On some iteration semigroups

Janusz Brzdęk (1995)

Archivum Mathematicum

Let F be a disjoint iteration semigroup of C n diffeomorphisms mapping a real open interval I onto I . It is proved that if F has a dense orbit possesing a subset of the second category with the Baire property, then F = { f t f t ( x ) = f - 1 ( f ( x ) + t ) for every x I , t R } for some C n diffeomorphism f of I onto the set of all reals R . The paper generalizes some results of J.A.Baker and G.Blanton [3].

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 .

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