Veneziano amplitude

In theoretical physics, the Veneziano amplitude refers to the discovery made in 1968 by Italian theoretical physicist Gabriele Veneziano that the Euler gamma 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:

k_n is a vector (such as a four-vector) referring to the momentum of the n^th 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.