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Descriptions of state spaces of orthomodular lattices (the hypergraph approach)

Mirko Navara (1992)

Mathematica Bohemica

Using the general hypergraph technique developed in [7], we first give a much simpler proof of Shultz's theorem [10]: Each compact convex set is affinely homeomorphic to the state space of an orthomodular lattice. We also present partial solutions to open questions formulated in [10] - we show that not every compact convex set has to be a state space of a unital orthomodular lattice and that for unital orthomodular lattices the state space characterization can be obtained in the context of unital...

Descriptive set-theoretical properties of an abstract density operator

Szymon Gła̧b (2009)

Open Mathematics

Let 𝒦 (ℝ) stand for the hyperspace of all nonempty compact sets on the real line and let d ±(x;E) denote the (right- or left-hand) Lebesgue density of a measurable set E ⊂ ℝ at a point x∈ ℝ. In [3] it was proved that { K 𝒦 ( ) : x K ( d + ( x , K ) = 1 o r d - ( x , K ) = 1 ) } is ⊓11-complete. In this paper we define an abstract density operator ⅅ± and we generalize the above result. Some applications are included.

Determinacy of adversarial Gowers games

Christian Rosendal (2014)

Fundamenta Mathematicae

We prove a game-theoretic dichotomy for G δ σ sets of block sequences in vector spaces that extends, on the one hand, the block Ramsey theorem of W. T. Gowers proved for analytic sets of block sequences and, on the other hand, M. Davis’ proof of Σ⁰₃ determinacy.

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