Erwin Schrödinger, at the University of Zurich, published in 1926 a formulation of quantum mechanics alternative to Heisenberg's matrix mechanics: instead of abstract matrices, he describes the state of a particle by means of a continuous wave function evolving according to a differential equation — the Schrödinger equation — a direct heir of Louis de Broglie's matter-wave hypothesis. The wave formulation proves much more intuitive and mathematically manageable for most physicists of the time, and Schrödinger soon shows that both formulations — his and Heisenberg's matrix version — are mathematically equivalent, two different languages describing the same underlying physics. Paul Dirac, at the University of Cambridge, published in 1928 a version of the wave equation incorporating Einstein's special relativity — absent from Schrödinger's original equation — necessary to correctly describe electrons moving at speeds close to that of light. The Dirac equation predicts, as an unexpected mathematical consequence, the existence of antimatter particles: the positron, with the same mass as the electron but opposite charge, would be discovered experimentally by Carl Anderson in 1932, confirming one of the most surprising theoretical predictions of 20th-century physics.