In this paper we introduce the $ℐ$- and ${ℐ}^{*}$-convergence and divergence of nets in $\left(\ell \right)$-groups. We prove some theorems relating different types of convergence/divergence for nets in $\left(\ell \right)$-group setting, in relation with ideals. We consider both order and $\left(D\right)$-convergence. By using basic properties of order sequences, some fundamental properties, Cauchy-type characterizations and comparison results are derived. We prove that ${ℐ}^{*}$-convergence/divergence implies $ℐ$-convergence/divergence for every ideal, admissible for...

We prove that for every Borel ideal, the ideal limits of sequences of continuous functions on a Polish space are of Baire class one if and only if the ideal does not contain a copy of Fin × Fin. In particular, this is true for $F_{\sigma \delta }$ ideals. In the proof we use Borel determinacy for a game introduced by C. Laflamme.

We find an analytic formulation of the notion of Hopf image, in terms of the associated idempotent state. More precisely, if π:A → Mₙ(ℂ) is a finite-dimensional representation of a Hopf C*-algebra, we prove that the idempotent state associated to its Hopf image A' must be the convolution Cesàro limit of the linear functional φ = tr ∘ π. We then discuss some consequences of this result, notably to inner linearity questions.

We consider an important subclass of self-similar, non-gaussian stable processes with stationary increments known as self-similar stable mixed moving averages. As previously shown by the authors, following the seminal approach of Jan Rosiński, these processes can be related to nonsingular flows through their minimal representations. Different types of flows give rise to different classes of self-similar mixed moving averages, and to corresponding general decompositions of these processes. Self-similar...

For any 1-1 measure preserving map T of a probability space we can form the [T,Id] and $[T,T^{-1}]$ automorphisms as well as the corresponding endomorphisms and decreasing sequence of σ-algebras. In this paper we show that if T has zero entropy and the [T,Id] automorphism is isomorphic to a Bernoulli shift then the decreasing sequence of σ-algebras generated by the [T,Id] endomorphism is standard. We also show that if T has zero entropy and the [T²,Id] automorphism is isomorphic to a Bernoulli shift then the...

Let $X=X\left(t\right),t\in {ℝ}^N$ be a Gaussian random field in ${ℝ}^d$ with stationary increments. For any Borel set $E\subset {ℝ}^N$, we provide sufficient conditions for the image X(E) to be a Salem set or to have interior points by studying the asymptotic properties of the Fourier transform of the occupation measure of X and the continuity of the local times of X on E, respectively. Our results extend and improve the previous theorems of Pitt [24] and Kahane [12,13] for fractional Brownian motion.

Having Polish spaces $𝕏$, $𝕐$ and $\mathbb{Z}$ we shall discuss the existence of an $𝕏\times 𝕐$-valued random vector $(\xi ,\eta )$ such that its conditional distributions $K_x=ℒ(\eta \mid \xi =x)$ satisfy $e(x,K_x)=c\left(x\right)$ or $e(x,K_x)\in C\left(x\right)$ for some maps $e:𝕏\times {ℳ}_1\left(𝕐\right)\to \mathbb{Z}$, $c:𝕏\to \mathbb{Z}$ or multifunction $C:𝕏\to 2^{\mathbb{Z}}$ respectively. The problem is equivalent to the existence of universally measurable Markov kernel $K:𝕏\to {ℳ}_1\left(𝕐\right)$ defined implicitly by $e(x,K_x)=c\left(x\right)$ or $e(x,K_x)\in C\left(x\right)$ respectively. In the paper we shall provide sufficient conditions for the existence of the desired Markov kernel. We shall discuss some special solutions of the $(e,c)$- or $(e,C)$-problem and illustrate...