  Motivated by the problem of identifying Majorana mode operators at junctions,
we analyze a basic algebraic structure leading to a doubled spectrum. For
general (nonlinear) interactions the emergent mode creation operator is highly
non-linear in the original effective mode operators, and therefore also in the
underlying electron creation and destruction operators. This phenomenon could
open up new possibilities for controlled dynamical manipulation of the modes.
We briefly compare and contrast related issues in the Pfaffian quantum Hall
state.
