DBAR problem

The DBAR problem, or the -problem, is the problem of solving the differential equation
for the function, where is assumed to be known and is a complex number in a domain. The operator is called the DBAR operator:
The DBAR operator is nothing other than the complex conjugate of the operator
denoting the usual differentiation in the complex -plane.
The DBAR problem is of key importance in the theory of integrable systems, Schrödinger operators and generalizes the Riemann–Hilbert problem.