Werner Heisenberg allotropic forms of hydrogen". Shortly after the discovery of the neutron by James Chadwick in 1932, Heisenberg submitted the first of three papers on his neutron-proton model of the nucleus. After Adolf Hitler came to power in 1933, Heisenberg was attacked in the press as a "White Jew". Supporters of "Deutsche Physik", or Aryan Physics, launched vicious attacks against leading theoretical physicists, including Arnold Sommerfeld and Heisenberg. From the early 1930s onward, the anti-Semitic and anti-theoretical physics movement "Deutsche Physik" had concerned itself with quantum mechanics and the theory of relativity. As applied in the university environment, political factors took
Spin (physics) do so. The study of the behavior of such "spin models" is a thriving area of research in condensed matter physics. For instance, the Ising model describes spins (dipoles) that have only two possible states, up and down, whereas in the Heisenberg model the spin vector is allowed to point in any direction. These models have many interesting properties, which have led to interesting results in the theory of phase transitions. In classical mechanics, the angular momentum of a particle possesses not only a magnitude (how fast the body is rotating), but also a direction (either up or down on