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Enclosure, separation, and computation of the zeros of exponential trinomials with constant coefficients and real exponential points

  • Fritz G. Boese
Published/Copyright: September 25, 2009

After having explained the underlying motivations, we study the location of the zeros of the functions T(z) := Aeaz+Bebz+Cecz of the complex variable z with complex coefficients A, B, C and real a < b < c. As normal form of T(z)=0 serves the equation e-pz/2·sinh (z/2)=P with a complex parameter P and a real p ∈ (-1,1). The problem of finding all solutions z of this equation is reduced to the calculation of the unique solution in a horizontal fundamental strip F := { z ∈ C: -π < Im(z) ≤ π }. By detailed estimations, we find tight enclosures for the zero in F. Series expansions and algorithms to find the zero z in F are propounded. A complete stability analysis for real trinomials is given. In a discussion, the problem is set into a wider perspective.

Received: 2006-9-29
Published Online: 2009-9-25
Published in Print: 2007-8-1

© Oldenbourg Wissenschaftsverlag

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