Bullough–Dodd model
The Bullough–Dodd model is an integrable model in 1+1-dimensional quantum field theory introduced by Robin Bullough and Roger Dodd. Its Lagrangian density is where formula_2 is a mass parameter, formula_3 is the coupling constant and formula_4 is a real scalar field. The Bullough–Dodd model belongs to the class of affine Toda field theories. The spectrum of the model consists of a single massive particle.