Tutkimuskuvaus
Most of physics is taught as if systems kept their energy to themselves. Real systems rarely do: light escapes from a laser, a vibrating string loses energy to friction, an excited atom decays. Such open systems can be described by so-called non-hermitian physics, and they behave in ways closed systems cannot.
I research which of these new behaviours are robust. The tool for this is topology, the mathematics of properties that do not change under deformation. I have shown, for instance, that the exceptional points, where energy levels merge, follow different rules from their closed-system counterparts, and how the symmetries of a crystal shapes their structure. Together with experimental colleagues, I have observed some of these effects in the laboratory.
At the University of Jyväskylä, I am now turning to systems that are not only open but also driven: shaken periodically in time, in what physicists call floquet systems. Repetition in time behaves much like repetition in space, and how the two combine in open systems is still largely uncharted.