Infinite lattices WIP

Former-commit-id: 39facbe563492f4fce54104fd4cf16d9cf1b951b

lepaper/infinite.lyx

@@ -320,6 +320,33 @@ noprefix "false"
 .
 \end_layout
 
+\begin_layout Standard
+As in the case of a finite system, eq.
+ can be written in a shorter block-matrix form,
+\begin_inset Formula 
+\[
+\left(I-WT\right)\outcoeffp{\vect 0}\left(\vect k\right)=\rcoeffincp{\vect 0}\left(\vect k\right)
+\]
+
+\end_inset
+
+ Eq.
+ 
+\begin_inset CommandInset ref
+LatexCommand eqref
+reference "eq:Multiple-scattering problem unit cell"
+plural "false"
+caps "false"
+noprefix "false"
+
+\end_inset
+
+ can be used to calculate electromagnetic response of the structure to external
+ quasiperiodic driving field – most notably a plane wave.
+ However, if one sets the right the right-hand side to zero, it can also
+ be used to find electromagnetic lattice modes
+\end_layout
+
 \begin_layout Subsection
 Computing the Fourier sum of the translation operator
 \begin_inset CommandInset label