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• # Artykuł - szczegóły

## Studia Mathematica

2015 | 228 | 2 | 153-175

## Multiple disjointness and invariant measures on minimal distal flows

EN

### Abstrakty

EN
We examine multiple disjointness of minimal flows, that is, we find conditions under which the product of a collection of minimal flows is itself minimal. Our main theorem states that, for a collection ${X_{i}}_{i∈I}$ of minimal flows with a common phase group, assuming each flow satisfies certain structural and algebraic conditions, the product $∏_{i∈I} X_{i}$ is minimal if and only if $∏_{i∈I} X_{i}^{eq}$ is minimal, where $X_{i}^{eq}$ is the maximal equicontinuous factor of $X_{i}$. Most importantly, this result holds when each $X_{i}$ is distal. When the phase group T is ℤ or ℝ, we can apply this idea to construct large minimal distal product flows with many ergodic measures. We determine the exact cardinality of (ergodic) invariant measures on the universal minimal distal T-flow. Equivalently, we determine the cardinality of (extreme) invariant means on 𝓓(T), the space of distal functions on T. This cardinality is $2^{𝔠}$ for both ergodic and invariant measures. The size of the quotient of 𝓓(T) by a closed subspace with a unique invariant mean is found to be non-separable by using the same techniques.

153-175

wydano
2015

### Twórcy

autor
• Department of Mathematical Sciences, University of Oulu, PL 8000, FI-90014 Oulun yliopisto, Finland