Let H be a complex, separable Hilbert space (of finite or infinite dimension), and let U(H) denote the group of unitary operators on H. In the finite-dimensional setting, we prove that every unitary operator of determinant one can be expressed as the product of two operators, each unitarily equivalent to the n × n unitary cycle. In the infinite-dimensional setting, we prove that every unitary operator U is a product of three operators, each unitarily equivalent to the bilateral shift, and if the spectrum of U has nonzero Lebesgue measure, then U is a product of two operators, each unitarily equivalent to the bilateral shift. This work is joint with Laurent Marcoux, Matjaž Omladič and Heydar Radjavi.
张远航,吉林大学数学学院教授,研究方向为算子理论和算子代数,目前主要研究兴趣是线性算子的结构、单核C*-代数分类、套代数的可逆元群连通性问题。研究成果发表于J. Funct. Anal.、J. Noncommut. Geom.、J.Operator Theory、Math. Z.、Proc. Amer. Math. Soc.、Sci.China Math.、Studia Math.及被Canad. J. Math.录用。