Computational and dynamical aspects of double-bracket flows
In this talk we report recent results and work in progress (joint with Tony Bloch) on various aspects of double-bracket flows and their generalisations. We present a computational algorithm, based on Magnus-type expansions of the underlying Lie algebra action and discuss different geometric and dynamical aspects of these flows. In particular we show that for the classical double-bracket flow Y′=[[N,Y],Y], where (without loss of generality) N is symmetric,
the distance ‖ is minimised along the isospectral orbit by the stable fixed point in all p-Schatten norms for p>1 (Brockett alredy proved this for p=2, i.e. the Frobenius norm), as well as classifying all symmetric gauges for which fixed points are optimal (in the above sense) for 2\times 2 matrices. We also consider generalised flows of the form Y'=[Y,[g(Y-N),Y]] and discuss their (nontrivial) dynamics.