Veneziano amplitude
In theoretical physics, the Veneziano amplitude refers to the discovery made in 1968 by Italian theoretical physicist Gabriele Veneziano that the Euler beta function, when interpreted as a scattering amplitude, has many of the features needed to explain the physical properties of strongly interacting mesons, such as symmetry and duality. Conformal symmetry was soon discovered. The formula is the following:
kn is a vector referring to the momentum of the nth particle. Γ is the gamma function.
This discovery can be considered the birth of string theory, as the discovery and invention of string theory came about as a search for a physical model which would give rise to such a scattering amplitude.