Toda field theory

In the study of field theory and partial differential equations, a Toda field theory is derived from the following Lagrangian:

:

Here "x" and "t" are spacetime coordinates, (,) is the Killing form of a real r-dimensional Cartan algebra $mathfrak\{h\}$ of a Kac-Moody algebra over $mathfrak\{h\}$, α_i is the i^th simple root in some root basis, n_i is the Coxeter number, m is the mass (or bare mass in the quantum field theory version) and β is the coupling constant.

Then a Toda field theory is the study of a function φ mapping 2 dimensional Minkowski space satisfying the corresponding Euler-Lagrange equations.

If the Kac-Moody algebra is finite, it's called a Toda field theory. If it is affine, it is called an affine Toda field theory (after the component of φ which decouples is removed) and if it is hyperbolic, it is called a hyperbolic Toda field theory.

Toda field theories are integrable models and their solutions describe solitons.

The sinh-Gordon model is the affine Toda field theory with the generalized Cartan matrix

:

and a positive value for β after we project out a component of φ which decouples.

The sine-Gordon model is the model with the same Cartan matrix but an imaginary β.

References

* [http://xstructure.inr.ac.ru/x-bin/theme2.py?arxiv=hep-th&level=2&index1=24 affine toda on arxiv.org]