ALBERT EINSTEIN (1879-1955). Autograph letter signed to Dr. Chaim Herman Müntz, in German. Signed A. Einstein. Written on thin paper in pencil. Einstein's letter contains a number of mathematical equations in his hand.
Dated 27. XII, 1928, 2 pages, c. 280 x 218 mm. Folded, small tears to fold. The letter begins: "Heureka Diesmal aber wirklich! Es stimmt nähmlich zu der ersten Näherung alles und die Lösung ist so prachtvoll, wie sie schöner nicht gedacht werden kann."

Provenance: A Swedish private collection.

Chaim Herman Müntz (28 August 1884, in Łódź – 17 April 1956, in Sweden), Polish-German mathematician, now remembered for the Müntz approximation theorem. He was active in Berlin and Munich and worked closely with Einstein in 1927. In 1929 he was appointed professor at the University of Leningrad where he worked until he was expelled as a German citizen in 1937 when he moved to Sweden where he lived for the rest of his life. He collaborated closely with Einstein in the years following 1927, and his help is acknowledged in a number of papers. Müntz also assisted Albert Einstein with complex mathemtical equations related to the physical theories he developed, including the unified field theory. In Einstein's published paper On Unified Field Theory (1929), the scientist expresses his appreciation of Muntz's 'laboriously precise calculation of the centrally symmetric problem on the basis of Hamilton's principle the results of his calculation suggested to me the method used here'.