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A López-Escobar theorem for metric structures, and the topological Vaught conjecture

Samuel Coskey, Martino Lupini (2016)

Fundamenta Mathematicae

We show that a version of López-Escobar’s theorem holds in the setting of model theory for metric structures. More precisely, let denote the Urysohn sphere and let Mod(,) be the space of metric -structures supported on . Then for any Iso()-invariant Borel function f: Mod(,) → [0,1], there exists a sentence ϕ of ω ω such that for all M ∈ Mod(,) we have f ( M ) = ϕ M . This answers a question of Ivanov and Majcher-Iwanow. We prove several consequences, for example every orbit equivalence relation of a Polish group...

A matrix formalism for conjugacies of higher-dimensional shifts of finite type

Michael Schraudner (2008)

Colloquium Mathematicae

We develop a natural matrix formalism for state splittings and amalgamations of higher-dimensional subshifts of finite type which extends the common notion of strong shift equivalence of ℤ⁺-matrices. Using the decomposition theorem every topological conjugacy between two d -shifts of finite type can thus be factorized into a finite chain of matrix transformations acting on the transition matrices of the two subshifts. Our results may be used algorithmically in computer explorations on topological...

A metric on the space of projections admitting nice isometries

Lajos Molnár, Werner Timmermann (2009)

Studia Mathematica

Motivated by the concept of separation between propositions in quantum logic, we introduce the so-called separation metric or Santos metric on the space of all projections in a Hilbert space. We show that the resulting metric space has only "nice" surjective isometries. On the nontrivial projections they are all unitarily or antiunitarily equivalent to the identity or to taking the orthogonal complement. We relate this result to Wigner's classical theorem on the form of quantum mechanical symmetry...

A metrizable completely regular ordered space

Hans-Peter A. Künzi, Stephen W. Watson (1994)

Commentationes Mathematicae Universitatis Carolinae

We construct a completely regular ordered space ( X , 𝒯 , ) such that X is an I -space, the topology 𝒯 of X is metrizable and the bitopological space ( X , 𝒯 , 𝒯 ) is pairwise regular, but not pairwise completely regular. (Here 𝒯 denotes the upper topology and 𝒯 the lower topology of X .)

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