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Zeros of solutions of a functional equation. (English) Zbl 1087.39022

The \(q\)-difference equation \[ \sum_{j=0}^m {a_j(x)~f(c^jx)} = Q(x)\tag{1} \] is considered in the class of transcendental entire functions. Here \(c \in {\mathbb C},~0 < |c| < 1\), and \(Q\) and the \(a_j\) are polynomials. Imposing conditions on the associated Newton-Puiseux diagram the authors show a theorem saying that (sub)sequences of zeros of solutions \(f\) to (1) are asymptotically comparable with certain geometric sequences. The proof is achieved by showing that \(f\) behaves asymptotically like a product of theta functions, \(\theta(z,q) = \sum_{n = - \infty} ^{+ \infty} {q^{n^2}z^n}\). The results are illustrated on three examples, the latter showing that the conditions imposed in the theorem on the Newton-Puiseux diagram are basically essential.

MSC:

39A13 Difference equations, scaling (\(q\)-differences)
39B32 Functional equations for complex functions
30D05 Functional equations in the complex plane, iteration and composition of analytic functions of one complex variable
33D90 Applications of basic hypergeometric functions
Full Text: DOI

References:

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