29  Domains

The domain \(\Omega\) in which we seek the solution to the Poisson equation, consists of \(n\) subdomains \(\Omega_i\), where the union of the subdomains is

\[ \Omega = \Omega_1 \cup \Omega_2 \cup \dots \cup \Omega_n \]

and the intersection of two subdomains is always

\[ \Omega_i \cap \Omega_k = \emptyset, \quad i \ne k. \]

Across the individual \(\Omega_i\) the physical parameters, e.g., conductivity, density, are usually constant.