Abstract:
We derive dispersionless Hirota equations for the extended dispersionless Toda hierarchy. We show that the dispersionless Hirota equations are just a direct consequence of the genus-zero topological recurrence relation for the topological $\mathbb CP^1$ model. Using the dispersionless Hirota equations, we compute the two-point functions and express the result in terms of Catalan numbers.
Keywords:
extended dispersionless Toda hierarchy, dispersionless Hirota equation, Catalan number, topological field theory.