Title | Topics in Interpolation Theory of Rational Matrix-valued Functions [electronic resource] / edited by I. Gohberg |
---|---|

Imprint | Basel : Birkhรคuser Basel : Imprint: Birkhรคuser, 1988 |

Connect to | http://dx.doi.org/10.1007/978-3-0348-5469-6 |

Descript | IX, 247 p. online resource |

SUMMARY

One of the basic interpolation problems from our point of view is the problem of building a scalar rational function if its poles and zeros with their multiplicities are given. If one assurnes that the function does not have a pole or a zero at infinity, the formula which solves this problem is (1) where Zl , " " Z/ are the given zeros with given multiplicates nl, " " n / and Wb" " W are the given p poles with given multiplicities ml, . . . ,m , and a is an arbitrary nonzero number. p An obvious necessary and sufficient condition for solvability of this simplest Interpolation pr- lern is that Zj :f: wk(1̃ j ̃ 1, 1̃ k̃ p) and nl +. . . +n/ = ml +. . . +m ' p The second problem of interpolation in which we are interested is to build a rational matrix function via its zeros which on the imaginary line has modulus 1. In the case the function is scalar, the formula which solves this problem is a Blaschke product, namely z z. )mi n u(z) = all = l̃ (2) J ( Z+ Zj where [o] = 1, and the zj's are the given zeros with given multiplicities mj. Here the necessary and sufficient condition for existence of such u(z) is that zp :f: - Zq for 1̃ ]1, q̃ n

Science
Science
Science general