Displaying similar documents to “On extremal positive maps acting between type I factors”

Decomposability of extremal positive unital maps on M₂(ℂ)

Władysław A. Majewski, Marcin Marciniak (2006)

Banach Center Publications

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A map φ: Mₘ(ℂ) → Mₙ(ℂ) is decomposable if it is of the form φ = φ₁ + φ₂ where φ₁ is a CP map while φ₂ is a co-CP map. It is known that if m = n = 2 then every positive map is decomposable. Given an extremal unital positive map φ: M₂(ℂ) → M₂(ℂ) we construct concrete maps (not necessarily unital) φ₁ and φ₂ which give a decomposition of φ. We also show that in most cases this decomposition is unique.

Estimating the extremal index through the tail dependence concept

Marta Ferreira (2015)

Discussiones Mathematicae Probability and Statistics

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The extremal index Θ is an important parameter in extreme value analysis when extending results from independent and identically distributed sequences to stationary ones. A connection between the extremal index and the tail dependence coefficient allows the introduction of new estimators. The proposed ones are easy to compute and we analyze their performance through a simulation study. Comparisons with other existing methods are also presented. Case studies within environment are considered...

Siciak's extremal function in complex and real analysis

W. Pleśniak (2003)

Annales Polonici Mathematici

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The Siciak extremal function establishes an important link between polynomial approximation in several variables and pluripotential theory. This yields its numerous applications in complex and real analysis. Some of them can be found on a rich list drawn up by Klimek in his well-known monograph "Pluripotential Theory". The purpose of this paper is to supplement it by applications in constructive function theory.