JF Ptak Science Books
von NEUMANN, John. "Einige Bemerkungen zur Diracschen Theorie des relativistischen Drehelektrons", in Zeitschrift fuer Physik, volume 48, 1928, pp 868-881, offered in the original volume of pp 891. The von Neumann section, band 11/12 for the year, comes with the original wrappers, bound in at the end. Cloth binding, small institutional gilt-stamped library slug at spine bottom, along with bookplate, and half-faded rubber stamps on the wrapper cover and on the title page. Still, a nice, free copy. $350
"Von Neumann’s most famous work in theoretical physics is his axiomatization of quantum mechanics. When he began work in that field in 1927, the methods used by its founders were hard to formulate in precise mathematical terms; “operator” on “functions” were handled without much consideration of their domain or definition to their topological properties: and it was blithely assumed that such “operators,” when self-adjoint, could always be “diagonalized” (as in th finite dimensional case), at the expense of introducing “Dirac functions” as “eigenvectors.” Von Neumann showed that mathematical rigor could be restored by taking as basic axioms the assumptions that the states of a physical system were poinds of a Hilbert space and that the measurable quantities were Hermitian (generally unbounded) operators densely efined in that space. This formalism. the practical use of which became available after von Neumann had developed the spectral theory of unbounded Hermitian operators (1929), has survived subsequent developments of quantum mechanics and is still the basisi of non relativistic quantum theory; with the introduction of the theory of distributions, it has even become possible to interpret its results in a way similar to Dirac’s original intuition"--Dictionary of Scientific Biography, volume 14, page 91.