Abstract
Let f be a real entire function with finitely many non-real zeros, not of the form f = Ph with P a polynomial and h in the Laguerre-Pólya class. Lower bounds are given for the number of non-real zeros of f″ + ω f, where ω is a positive real constant.
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Langley, J.K. Non-real zeros of linear differential polynomials. J Anal Math 107, 107–140 (2009). https://doi.org/10.1007/s11854-009-0005-4
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DOI: https://doi.org/10.1007/s11854-009-0005-4