Abstract
Let K be a field of characteristic p>0 and let f(t 1,…,t d ) be a power series in d variables with coefficients in K that is algebraic over the field of multivariate rational functions K(t 1,…,t d ). We prove a generalization of both Derksen’s recent analogue of the Skolem–Mahler–Lech theorem in positive characteristic and a classical theorem of Christol, by showing that the set of indices (n 1,…,n d )∈ℕd for which the coefficient of \(t_{1}^{n_{1}}\cdots t_{d}^{n_{d}}\) in f(t 1,…,t d ) is zero is a p-automatic set. Applying this result to multivariate rational functions leads to interesting effective results concerning some Diophantine equations related to S-unit equations and more generally to the Mordell–Lang Theorem over fields of positive characteristic.
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The First author was supported by ANR grants Hamot and SubTile. The second author was supported by NSERC grant 31-611456.
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Adamczewski, B., Bell, J.P. On vanishing coefficients of algebraic power series over fields of positive characteristic. Invent. math. 187, 343–393 (2012). https://doi.org/10.1007/s00222-011-0337-4
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DOI: https://doi.org/10.1007/s00222-011-0337-4