Classical unified field theories version of the general-relativistic field equation expressed the property that the universe was "self-gauging". Since the simplest cosmological model (the De Sitter universe) that solves that equation is a spherically symmetric, stationary, closed universe (exhibiting a cosmological red shift, which is more conventionally interpreted as due to expansion), it seemed to explain the overall form of the universe. Like many other classical unified field theorists, Eddington considered that in the Einstein field equations for general relativity the stress–energy tensor formula_1, which represents matter/energy, was merely provisional, and that in a truly unified theory the source term would automatically arise as
History of quantum field theory with his numerous and failed attempts at a classical unified field theory, was simply out of the question. "Fields had to be quantized". The third thread in the development of quantum field theory was the need to handle the statistics of many-particle systems consistently and with ease. In 1927, Pascual Jordan tried to extend the canonical quantization of fields to the many-body wave functions of identical particles using a formalism which is known as statistical transformation theory; this procedure is now sometimes called second quantization. In 1928, Jordan and Eugene Wigner found that the quantum field describing electrons, or other