On 2D Inverse Problems/Notation

$\mathbb{N} \mbox{ is the set of natural numbers}$
$\mathbb{Z} \mbox{ is the set of integers}$
$\mathbb{R} \mbox{ is the set of real numbers}$
$\mathbb{C} \mbox{ is the set of complex numbers}$
$k, l, m, \dots \mbox{ are integers}$
$a,b,\ldots, \alpha, \beta, \ldots \mbox{ are real and complex numbers and functions}$
$\mathbb{C}^+=\{z \in \mathbb{C}, \Re(z) \ge 0\} \mbox{ is the complex right half-plane}$
$\mathbb{D}=\{z \in \mathbb{C}, |z| < 1\} \mbox{ is the open unit disc}$
$\omega \mbox{ is a root of unity}$
$M \mbox{ is a surface (2D manifold)}$
$\nabla \mbox{ is the gradient}$
$\Delta \mbox{ is the Laplace operator}$
$\Lambda \mbox{ is Dirichlet-to-Neumann operator}$
$P, Q \mbox{ are ordered subsets of integers}$
$A, B, \ldots \mbox{ are matrices}$
$A(P, Q) \mbox{ is a submatrix of matrix } A$
$W(G) \mbox{ is a matrix of exiting probabilities}$
$D_x \mbox{ is a diagonal matrix such that } D_x 1 = x$
$D_A \mbox{ is a diagonal matrix coinciding on diagonal w/matrix } A$
$\lambda \mbox{ is an eigenvalue}$
$\sigma(A) \mbox{ is the spectrum of matrix } A$
$\rho(A) \mbox{ is the characteristic polynomial of matrix } A$
$P \mbox{ is a permutation matrix}$
$C(A) \mbox{ is a compound matrix of matrix } A$
$F \mbox{ is the Fourier transform}$
$H \mbox{ is the Hilbert transform}$
$\tau \mbox{ is the Cayley transform}$
$\Omega \mbox{ is a continuous domain}$
$H^k(\Omega) \mbox{ is a weighted space}$
$G/G^* \mbox{ is graph or network and its dual}$
$V \mbox{ is the set of vertices of a graph}$
$E \mbox{ is the set of edges of a graph}$
$w \mbox{ is weight function}$
$M(G) \mbox{ is the medial graph of graph ''G''}$
$\gamma \mbox{ is a conductivity function}$
$u, v \mbox{ are harmonic functions}$
$q \mbox{ is a potential function}$