This article uses the Einstein summation convention for tensor/spinor indices, and uses hats for quantum operators.In relativistic quantum mechanics and quantum field theory, the Bargmann–Wigner equations describe free particles of arbitrary spin j, an integer for bosons (j = 1, 2, 3 ...) or half-integer for fermions (j = 1⁄2, 3⁄2, 5⁄2 ...). The solutions to the equations are wavefunctions, mathematically in the form of multi-component spinor fields. They are named after Valentine Bargmann and Eugene Wigner. == History == Paul Dirac first published the Dirac equation in 1928, and later (1...

The Course of Theoretical Physics is a ten-volume series of books covering theoretical physics that was initiated by Lev Landau and written in collaboration with his student Evgeny Lifshitz starting in the late 1930s. It is said that Landau composed much of the series in his head while in an NKVD prison in 1938-1939. However, almost all of the actual writing of the early volumes was done by Lifshitz, giving rise to the witticism, "not a word of Landau and not a thought of Lifshitz". The first eight volumes were finished in the 1950s, written in Russian and translated into English in the late 1950s...

Continuous spin particle (or CSP in short), sometimes called an infinite spin particle, is known as a massless particle never observed before in nature. This particle is one of Poincaré group's massless representations which along with ordinary massless particles was classified by Eugene Wigner in 1939. Historically, a compatible theory that could describe this elementary particle was unknown, however, 75 years after Wigner's classification, the first local action principle for bosonic continuous spin particles was introduced in 2014, and the first local action principle for fermionic continuous...