Pascual Jordan (b.
October 18, 1902 in
Hanover, Germany; d.
July 31, 1980 in
Hamburg, Federal Republic of Germany) was a theoretical and mathematical
physicist who made significant contributions to
quantum mechanics and
quantum field theory.
Jordan's great-grandfather Pascual Jorda was a
Spanish nobleman and cavalry officer who served with the
British during and after the
Napoleonic Wars. Jorda eventually settled in Hanover which in those days was a possession of the
British royal family. His patrilineal descendants held to a tradition of naming their first-born sons Pascual, while their family name was eventually changed to Jordan (pronounced in the German manner, "YOUR-den").
Jordan enrolled in the
Hanover Technical University in
1921 where he studied an eclectic mix of
zoology, mathematics, and
physics. As was typical for a German university student of the time, he transferred before obtaining a degree.
Göttingen University, his destination in
1923, was then at the very zenith of its prowess and fame in mathematics and the physical sciences. Here, Jordan became an assistant to firstly the mathematician
Richard Courant and then the physicist Max Born.
Together with
Max Born and
Werner Heisenberg he was co-author of an important series of papers on
quantum mechanics. He went on to pioneer early
quantum field theory before largely switching his focus to
cosmology before World War II.
Jordan joined the NSDAP (Nazi Party) in May
1933. The following November he joined the
Sturmabteilung (SA) - the brown shirted storm troopers. He enlisted in the
Luftwaffe in
1939 and worked for a while at the
Peenemünde rocket center. During the war he attempted to interest the party in various schemes for advanced weapons, but these were ignored because he was considered "politically unreliable", probably because of his past associations with Jews (in particular: Courant, Born, and
Wolfgang Pauli) and "Jewish Physics" (such a stigma also followed Werner Heisenberg for some time under the Nazis) (see the article
Deutsche Physik).
It has been speculated that Jordan would have likely shared the
1954 Nobel Prize in Physics awarded to Max Born were it not for his membership in the Nazi party (see both J. Bernstein and B. Schroer references).
Wolfgang Pauli declared Jordan "rehabilitated" to the authorities some time after the war, allowing Jordan to regain academic employment after a two-year period and then recover his full status as a tenured professor in
1953. Jordan went against Pauli's advice, and reentered politics after the period of
denazification came to an end under the pressures of the
Cold War. He secured election to the
Bundestag standing with the
conservative Christian Democrats. In
1957, Jordan came out in support for the arming of the
Bundeswehr with
tactical nuclear weapons by the
Adenauer government, while the
Göttinger 18 (which included Born, Heisenberg, and Pauli) authored the
Göttinger Manifest in protest. This and other issues were to further strain his relationships with his former friends and colleagues.
The non-associative
Jordan algebras are named after him. They were defined in an attempt to create an algebra of observables for quantum mechanics and quantum field theory. Today, this role is more often assumed by the
von Neumann algebras. Meanwhile, Jordan algebras have seen application in
projective geometry and
number theory.
Jordan is sometimes confused with the French mathematician
Camille Jordan (
Jordan curve theorem) and the German
geodesist Wilhelm Jordan (
Gauss-Jordan elimination). 
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