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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

{\mathcal {L}}={\frac {1}{2}}(\partial _{\mu }\varphi )^{2}-{\frac {m_{0}^{2}}{6g^{2}}}(2e^{g\varphi }+e^{-2g\varphi })

where $m_{0}\,$ is a mass parameter, $g\,$ is the coupling constant and $\varphi \,$ 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.

References

Dodd, R. K.; Bullough, R. K. (4 February 1977). "Polynomial Conserved Densities for the Sine-Gordon Equations". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 352 (1671). The Royal Society: 481–503. Bibcode:1977RSPSA.352..481D. doi:10.1098/rspa.1977.0012. ISSN 1364-5021. S2CID 123071322.
Fring, A.; Mussardo, G.; Simonetti, P. (1993). "Form factors of the elementary field in the Bullough-Dodd model". Physics Letters B. 307 (1–2). Elsevier BV: 83–90. arXiv:hep-th/9303108. Bibcode:1993PhLB..307...83F. doi:10.1016/0370-2693(93)90196-o. ISSN 0370-2693. S2CID 16396002.