Abstract:
We study real Hurwitz numbers enumerating real meromorphic functions of a special kind, referred to as
framed purely real functions. We deduce partial differential equations of cut-and-join type for the generating
functions for these numbers. We also construct a topological field theory for them.
Keywords:
simple Hurwitz number, real algebraic curve, real meromorphic function, real simple Hurwitz number, cut-and-join
equation.
While preparing this paper, S. M. Natanzon was partly supported by the Russian Foundation for Basic
Research, grant no. 20-01-00579, and enjoyed the hospitality of Institut des Hautes Études Scientifiques (Paris, France). The results of S. K. Lando presented in § 2 were obtained with the support of RSF-ANR grant no. 20-41-09009.