Hurwitz polynomial

In mathematics, a Hurwitz polynomial (named after German mathematician Adolf Hurwitz) is a polynomial whose roots (zeros) are located in the left half-plane of the complex plane or on the imaginary axis, that is, the real part of every root is zero or negative.[1] Such a polynomial must have coefficients that are positive real numbers. The term is sometimes restricted to polynomials whose roots have real parts that are strictly negative, excluding the imaginary axis (i.e., a Hurwitz stable polynomial).[2][3]

A polynomial function P(s) of a complex variable s is said to be Hurwitz if the following conditions are satisfied:

  1. P(s) is real when s is real.
  2. The roots of P(s) have real parts which are zero or negative.

Hurwitz polynomials are important in control systems theory, because they represent the characteristic equations of stable linear systems. Whether a polynomial is Hurwitz can be determined by solving the equation to find the roots, or from the coefficients without solving the equation by the Routh–Hurwitz stability criterion.

  1. ^ Kuo, Franklin F. (1966). Network Analysis and Synthesis, 2nd Ed. John Wiley & Sons. pp. 295–296. ISBN 0471511188.
  2. ^ Weisstein, Eric W (1999). "Hurwitz polynomial". Wolfram Mathworld. Wolfram Research. Retrieved July 3, 2013.
  3. ^ Reddy, Hari C. (2002). "Theory of two-dimensional Hurwitz polynomials". The Circuits and Filters Handbook, 2nd Ed. CRC Press. pp. 260–263. ISBN 1420041401. Retrieved July 3, 2013.