who became a professor at the University of Leipzig and, after World War II, at the Kaiser Wilhelm Institute in Göttingen. In 1932 he was awarded the Nobel Prize for physics for his work on matrix mechanics, but he is best known for his 1927 discovery of the uncertainty principle. He also did fundamental work on ferromagnetism, nuclear theory, and quantum electrodynamics. His attempts to construct a unified-field theory were unsuccessful but introduced the concept of broken symmetry into the theory of elementary particles.