# On 2D Inverse Problems/Notation

${\displaystyle \mathbb {N} {\mbox{ of natural numbers}}}$
${\displaystyle \mathbb {D} {\mbox{ is the open disc domain}}}$
${\displaystyle \mathbb {b} {\mbox{ is the open domain nature boundary}}}$
${\displaystyle \mathbb {C} ^{\pm }{\mbox{ is the complex half-plane}}}$
${\displaystyle mega{\mbox{ is a root of unity}}}$
${\displaystyle \nabla {\mbox{ is the gradient}}}$
${\displaystyle \Delta =\nabla \cdot \nabla {\mbox{ is the Laplace operator}}}$
${\displaystyle \Lambda {\mbox{ is Dirichlet-to-Neumann operator}}}$
${\displaystyle D_{x}{\mbox{ is a diagonal matrix w/the vector }}x{\mbox{ on the diagonal }}(D_{x}1=x)}$
${\displaystyle D_{A}{\mbox{ is the diagonal matrix, coinciding on diagonal w/the matrix }}A}$
${\displaystyle y,\lambda {\mbox{ is eigenvalue of operator/matrix}}}$
${\displaystyle ma(A){\mbox{ is spectrum of matrix }}A,{\mbox{ zeros of characteristic polynomial }}}$
${\displaystyle \rho (A){\mbox{ is the characteristic polynomial of matrix }}A}$
${\displaystyle \tau {\mbox{ is the Cayley transform}}}$
${\displaystyle ega{\mbox{ is a continuous domain}}}$
${\displaystyle G/G^{*}{\mbox{ is graph or network and its dual}}}$
${\displaystyle V_{G}{\mbox{ is the set of vertices of a graph}}}$
${\displaystyle E_{G}{\mbox{ is the set of edges of a graph}}}$
${\displaystyle M_{G}{\mbox{ is the medial graph of an embedded graph }}G}$
${\displaystyle c{\mbox{ is conductivity}}}$