We find all formal solutions to the $\hbar$-dependent Kadomtsev-Petviashvili (KP) hierarchies. For $\hbar=1$ and $\hbar=0$ they are solutions of standard KP hierarchy and dispersionless KP hierarchy respectively. The solutions are characterized by certain Cauchy-like data that are functions of one variable. The solutions are found in a form of formal series for the tau-functions of the hierarchies and for its logarithms. An explicit combinatorial description of the coefficients of the series is provided. The talk is based on join work with A.Zabrodin.
Links:
[1] http://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] http://www.mpim-bonn.mpg.de/de/node/3444
[3] http://www.mpim-bonn.mpg.de/de/node/5312