Green functions of the spectral ball and symmetrized polydisk

Pascal J. Thomas (1) , Nguyen van Trao (2) , Wlodzimierz Zwonek (3)

1 IMT - Institut de Mathématiques de Toulouse UMR5219
2 DHSP - Laboratory of Complex Geometry
3 Instytut Matematyki

The Green function of the spectral ball is constant over the isospectral varieties, is never less than the pullback of its counterpart on the symmetrized polydisk, and is equal to it in the generic case where the pole is a cyclic (non-derogatory) matrix. When the pole is derogatory, the inequality is always strict, and the difference between the two functions depends on the order of nilpotence of the strictly upper triangular blocks that appear in the Jordan decomposition of the pole. In particular, the Green function of the spectral ball is not symmetric in its arguments. Additionally, some estimates are given for invariant functions in the symmetrized polydisc, e.g. (infinitesimal versions of) the Carathéodory distance and the Green function, that show that they are distinct in dimension greater or equal to $3$.

Mots clés: Green functions; spectral ball; plurisubharmonic functions; symmetrized polydisk

Domaines: Variables complexes [math.CV]

Pascal J. Thomas, Nguyen van Trao, Wlodzimierz Zwonek. Green functions of the spectral ball and symmetrized polydisk. Journal of Mathematical Analysis and Applications, 2011, 377 (2), pp.624-630. ⟨10.1016/j.jmaa.2010.11.020⟩. ⟨hal-00950108⟩