Abstract:We show that, whenever Γ is a countable abelian group and ∆ ≤ Γ is a finitely-generated subgroup, a generic measure-preserving action of ∆ on a standard atomless probability space (X, µ) extends to a free measure-preserving action of Γ on (X, µ). This extends a result of Ageev, corresponding to the case when ∆ is infinite cyclic.2010 Mathematics Subject Classification. 22F10, 54H11. Key words and phrases. Measure-preserving action, genericity in the space of actions, extensions of actions.1 Ageev did not publi… Show more
“…, we get (26) for any ξ ′ k -measurable set A. Since ξ ′ n → ε, by the diagonal process, we have a universal sequence g(n) and ( 25) implies (24).…”
Section: Let Us Modify Each Tmentioning
confidence: 97%
“…Recently Melleray proved Theorem 1.2 for H being finitely-generated via categorypreserving maps and a generalization of the classical Kuratowski-Ulam theorem (see [26]).…”
For every countable abelian group G we find the set of all its subgroups H (H ≤ G) such that a typical measure-preserving H-action on a standard atomless probability space (X, F , µ) can be extended to a free measure-preserving G-action on (X, F , µ). The description of all such pairs H ≤ G was made in purely group terms, in the language of the dual G, and G-actions with discrete spectrum. As an application, we answer a question when a typical H-action can be extended to a G-action with some dynamic property, or to a G-action at all. In particular, we offer first examples of pairs H ≤ G satisfying both G is countable abelian, and a typical H-action is not embeddable in a G-action.
“…, we get (26) for any ξ ′ k -measurable set A. Since ξ ′ n → ε, by the diagonal process, we have a universal sequence g(n) and ( 25) implies (24).…”
Section: Let Us Modify Each Tmentioning
confidence: 97%
“…Recently Melleray proved Theorem 1.2 for H being finitely-generated via categorypreserving maps and a generalization of the classical Kuratowski-Ulam theorem (see [26]).…”
For every countable abelian group G we find the set of all its subgroups H (H ≤ G) such that a typical measure-preserving H-action on a standard atomless probability space (X, F , µ) can be extended to a free measure-preserving G-action on (X, F , µ). The description of all such pairs H ≤ G was made in purely group terms, in the language of the dual G, and G-actions with discrete spectrum. As an application, we answer a question when a typical H-action can be extended to a G-action with some dynamic property, or to a G-action at all. In particular, we offer first examples of pairs H ≤ G satisfying both G is countable abelian, and a typical H-action is not embeddable in a G-action.
“…Below, we focus on the first case only; the second case is handled by analogous methods. By the definition of µ y ⊗ µ z and since basic sets form a topological basis of C x , it is enough to show that (19) hῑ…”
Section: The Theorem On Koopman Representations and An Outline Of Its Proofmentioning
confidence: 99%
“…Unpacking further, we see that showing inequality (19) boils down to showing that, for each compact subset K of U with µ U,ῑ K > 0, there is some j ∈ N with µ j x (K) > 0. This translates into proving the following implication for each compact set K ⊆ U (20)…”
Section: The Theorem On Koopman Representations and An Outline Of Its Proofmentioning
We prove that for a generic measure preserving transformation $T$, the closed
group generated by $T$ is a continuous homomorphic image of a closed linear
subspace of $L_0(\lambda,{\mathbb R})$, where $\lambda$ is Lebesgue measure,
and that the closed group generated by $T$ contains an increasing sequence of
finite dimensional toruses whose union is dense
“…validated their experimental results of Raman analysis of pharmaceutical tablets along with the reflection of exiting photons back into the medium through RMC simulations. Photon propagation in breast tissue was simulated by Keller et al . to study the application of SORS in mastectomy to monitor the tumor margin.…”
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