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A Cyclic Subnormal Completion of Complex Data

  • Jung, Il Bong (Department of Mathematics, Kyungpook National University) ;
  • Li, Chunji (Institute of System Science, Northeastern University) ;
  • Park, Sun Hyun (Department of Mathematics, Kyungpook National University)
  • Received : 2013.07.09
  • Accepted : 2013.09.17
  • Published : 2014.06.23

Abstract

For a finite subset ${\Lambda}$ of $\mathbb{N}_0{\times}\mathbb{N}_0$, where $\mathbb{N}_0$ is the set of nonnegative integers, we say that a complex data ${\gamma}_{\Lambda}:=\{{\gamma}_{ij}\}_{(ij){\in}{\Lambda}}$ in the unit disc $\mathbf{D}$ of complex numbers has a cyclic subnormal completion if there exists a Hilbert space $\mathcal{H}$ and a cyclic subnormal operator S on $\mathcal{H}$ with a unit cyclic vector $x_0{\in}\mathcal{H}$ such that ${\langle}S^{*i}S^jx_0,x_0{\rangle}={\gamma}_{ij}$ for all $i,j{\in}\mathbb{N}_0$. In this note, we obtain some sufficient conditions for a cyclic subnormal completion of ${\gamma}_{\Lambda}$, where ${\Lambda}$ is a finite subset of $\mathbb{N}_0{\times}\mathbb{N}_0$.

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References

  1. J. Bram, Subnormal operators, Duke Math. J., 22(1955), 75-94. https://doi.org/10.1215/S0012-7094-55-02207-9
  2. R. Curto and L. Fialkow, Recursively generated weighted shifts and the subnormal completion problem, I, Integr. Equ. Oper. Theory, 17(1993), 202-246. https://doi.org/10.1007/BF01200218
  3. R. Curto and L. Fialkow, Recursively generated weighted shifts and the subnormal completion problem, II, Integr. Equ. Oper. Theory, 18(1994), 369-426. https://doi.org/10.1007/BF01200183
  4. R. Curto and L. Fialkow, Solution of the truncated complex moment problems for flat data, Memoirs Amer. Math. Soc., 568(1996).
  5. R. Curto and L. Fialkow, Flat extensions of positive moment matrices: recursively generated relations, Memoirs Amer. Math. Soc., 648(1998).
  6. M. Embry, A generalization of the Halmos-Bram criterion for subnormality, Acta. Sci. Math., (Szeged) 31(1973), 61-64.
  7. I. B. Jung, C. Li, and S. Park, Complex moment matrices via Halmos-Bram and Embry conditions, J. Korean Math. Soc., 44(2007), 949-970. https://doi.org/10.4134/JKMS.2007.44.4.949
  8. I. B. Jung, E. Ko, C. Li and S. S. Park, Embry truncated complex moment problem, Linear Algebra Appl., 375(2003), 95-114. https://doi.org/10.1016/S0024-3795(03)00617-7
  9. P. Halmos, Normal dilations and extensions of operators, Summa Bras. Math., 2(1950), 124-134.
  10. C. Li and S. H. Lee, The quartic moment problem, J. Korean Math. Soc., 42(2005), 723-747. https://doi.org/10.4134/JKMS.2005.42.4.723
  11. J. Stampfli, Which weighted shifts are subnormal? Pacific J. Math., 17(1966), 367-379. https://doi.org/10.2140/pjm.1966.17.367