,
Bernard Hanzon
,
Eike Neumann
Creative Commons Attribution 4.0 International license
We establish Diophantine hardness results for the decidability of the Positivity Problem for exponential-trigonometric polynomials over computable discrete subfields of the real numbers, and for related questions. We show that any algorithm for deciding either non-negativity, eventual non-negativity, the existence of a zero, or the existence of infinitely many zeros of exponential-trigonometric polynomials over a computable discrete subfield K of the reals containing the number π can be translated into an algorithm for computing the irrationality exponents of all elements of K. As a consequence, we exhibit a computable discrete subfield K of the reals such that all of the aforementioned questions about exponential-trigonometric polynomials over K are undecidable. In particular, we provide the first example of a natural generalisation of the Continuous Skolem Problem that is provably undecidable.
@InProceedings{collins_et_al:LIPIcs.MFCS.2026.65,
author = {Collins, Pieter and Hanzon, Bernard and Neumann, Eike},
title = {{On Positivity of Exponential-Trigonometric Polynomials and Irrationality Exponents}},
booktitle = {51st International Symposium on Mathematical Foundations of Computer Science (MFCS 2026)},
pages = {65:1--65:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-442-0},
ISSN = {1868-8969},
year = {2026},
volume = {386},
editor = {Kouck\'{y}, Michal and Petrișan, Daniela},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2026.65},
URN = {urn:nbn:de:0030-drops-274478},
doi = {10.4230/LIPIcs.MFCS.2026.65},
annote = {Keywords: Linear Dynamical Systems, Computability, Computable Numbers, Transcendental Numbers, Irrationality Measure, Irrationality Exponent}
}