History of subatomic physics indestructible. But when the nucleus change its charge and/or mass (by emitting or capturing a particle), the atom can become the one of another element. Special relativity explained how the "mass defect" is related to the energy produced or consumed in reactions. The branch of physics that studies transformations and the structure of nuclei is now called nuclear physics, contrasted to atomic physics that studies the structure and properties of atoms ignoring most nuclear aspects. The development in the nascent quantum physics, such as Bohr model, led to the understanding of chemistry in terms of the arrangement of electrons in
Heisenberg group unitary operator of formula_103 that commutes with them is an formula_121 multiplier. But commuting with translations implies that the multiplier is constant. A version of the Stone–von Neumann theorem, proved by George Mackey, holds for the Heisenberg group formula_113. The Fourier transform is the unique intertwiner between the representations of formula_103 and formula_124. See the discussion at Stone–von Neumann theorem#Relation to the Fourier transform for details. Heisenberg group In mathematics, the Heisenberg group formula_1, named after Werner Heisenberg, is the group of 3×3 upper triangular matrices of the form under the operation of matrix multiplication. Elements "a, b" and "c"