# Phase boundaries in algebraic conformal QFT

May 30, 2014

We study the structure of local algebras in relativistic conformal quantum
field theory with phase boundaries. Phase boundaries (or "defects") are
instances of a more general notion of boundaries, that give rise to quite a
variety of algebraic structures. These can be formulated in a common framework
originating in Algebraic QFT, with the principle of Einstein Causality playing
a prominent role. We classify the phase boundary conditions by the centre of a
certain universal construction, which produces a reducible representation in
which all possible boundary conditions are realized. While the classification
itself reproduces results obtained in a different framework by other authors
before (because the underlying mathematics turns out to be the same), the
physical interpretation is quite different.
Dedicated to Detlev Buchholz on the occasion of his 70th birthday.

Keywords:

rational conformal field theories, algebraic quantum field theory, boundary conditions, defects, phase boundaries