History of quantum field theory
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 fermions, had to be expanded using anti-commuting creation and annihilation operators due to the Pauli exclusion principle (see Jordan–Wigner transformation). This thread of development was incorporated into many-body theory and strongly influenced condensed matter physics and nuclear physics.
Suraj N. Gupta
Gupta introduced in 1950, simultaneously and independently of Konrad Bleuler, the Gupta–Bleuler quantization of the quantum electrodynamics (QED) that takes the covariant Lorenz gauge condition on an indefinite metric in Hilbert space of states realized. From it came some of the first attempts, to derive the equations of general relativity from quantum field theory for a massless spin two particle (graviton). Similar work has also led Robert Kraichnan in the 1940s (not published until 1955) and later in the 1960s, by Richard Feynman and Steven Weinberg. Later he worked in various areas of quantum field theory and elementary particle physics, including quantum chromodynamics and quarkonium.