2007/07/23 by Michael T. Jury, Jury, Michael T. · 2 citations
Mathematics · #Holomorphic and Operator Theory #Advanced Topics in Algebra #Advanced Operator Algebra Research
paper · pdf · doi:10.48550/arxiv.0707.3426
We prove that the norm of a weighted composition operator on the Hardy space H2 of the disk is controlled by the norm of the weight function in the de Branges-Rovnyak space associated to the symbol of the composition operator. As a corollary we obtain a new proof of the boundedness of composition operators on H2, and recover the standard upper bound for the norm. Similar arguments apply to weighted Bergman spaces. We also show that the positivity of a generalized de Branges-Rovnyak kernel is sufficient for the boundedness of a given composition operator on the standard functions spaces on the unit ball.