## Jordan algebras

In Kevin McCrimmon's excellent book

*A Taste of Jordan Algebras*(2004) he describes how Pascual Jordan's study of quantum mechanics led to the definition of Jordan algebras. These have been of great importance in mathematics but it was eventually shown by Efim Zelmanov in 1983 that they they could never provide a setting for quantum mechanics. McCrimmon writes:In 1932 the physicist Pascual Jordan proposed a program to discover a new algebraic setting for quantum mechanics, which would be freed from dependence on an invisible all-determining metaphysical matrix structure, yet would enjoy all the same algebraic benefits as the highly successful Copenhagen model. He wished to study the intrinsic algebraic properties of hermitian matrices, to capture these properties in formal algebraic properties, and then to see what other possible non-matrix systems satisfied these axioms. The first step in analyzing the algebraic properties of hermitian matrices or operators was to decide what the basic observable operations were. There are many possible ways of combining hermitian matrices to get another hermitian matrix, but after some empirical experimentation Jordan decided that they could all be expressed in terms of quasi-multiplication

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