International Journal of Theoretical Physics

, Volume 44, Issue 12, pp 2199–2206 | Cite as

Open Problems for Sequential Effect Algebras

  • Stan Gudder


A sequential effect algebra (SEA) is an effect algebra on which a sequential product with certain natural properties is defined. In such structures, we can study combinations of simple measurements that are series as well as parallel. This article presents some open problems for SEAs together with background material, comments and partial results. Two examples of open problems are the following: is AB = A 1/2 BA 1/2 the only sequential product on a Hilbert space SEA? It is known that the sharp elements of a SEA form an orthomodular poset. Is every orthomodular poset isomorphic to the set of sharp elements for some SEA?


effect algebras sequential effect algebras positive operators quantum effects 


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Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  1. 1.Department of MathematicsUniversity of DenverDenver

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