Abstract
A synaptic algebra is an abstract version of the partially ordered Jordan algebra of all bounded Hermitian operators on a Hilbert space. We review the basic features of a synaptic algebra and then focus on the interaction between a synaptic algebra and its orthomodular lattice of projections. Each element in a synaptic algebra determines and is determined by a one-parameter family of projections—its spectral resolution. We observe that a synaptic algebra is commutative if and only if its projection lattice is boolean, and we prove that any commutative synaptic algebra is isomorphic to a subalgebra of the Banach algebra of all continuous functions on the Stone space of its boolean algebra of projections. We study the so-called range-closed elements of a synaptic algebra, prove that (von Neumann) regular elements are range-closed, relate certain range-closed elements to modular pairs of projections, show that the projections in a synaptic algebra form an M-symmetric orthomodular lattice, and give several sufficient conditions for modularity of the projection lattice.
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The second author was supported by Research and Development Support Agency under the contract No. APVV-0071-06, grant VEGA 2/6088/26 and Center of Excellence SAS, CEPI I/2/2005.
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Foulis, D.J., Pulmannová, S. Projections in a Synaptic Algebra. Order 27, 235–257 (2010). https://doi.org/10.1007/s11083-010-9148-2
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DOI: https://doi.org/10.1007/s11083-010-9148-2
Keywords
- C*-algebra
- von Neumann algebra
- Base-normed space
- Jordan algebra
- Projection
- Orthomodular lattice
- Carrier projection
- Polar decomposition
- Symmetry
- Regular element
- Residuated mapping
- Sasaki projection
- Range-closed element
- Modular and dual modular pairs
- Modular lattice
- M-symmetric