Exponentially-improved asymptotics for q-difference equations: 2ϕ0 and qPI

Usually when solving differential or difference equations via series solutions one encounters divergent series in which the coefficients grow like a factorial. Surprisingly, in the q-world the nth coefficient is often of the size q−12n(n−1), in which q∈(0,1) is fixed. Hence, the divergence is much s...

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Vydáno v:Indagationes mathematicae Ročník 36; číslo 6; s. 1555 - 1571
Hlavní autoři: Joshi, Nalini, Olde Daalhuis, Adri
Médium: Journal Article
Jazyk:angličtina
Vydáno: Elsevier B.V 01.11.2025
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ISSN:0019-3577
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Shrnutí:Usually when solving differential or difference equations via series solutions one encounters divergent series in which the coefficients grow like a factorial. Surprisingly, in the q-world the nth coefficient is often of the size q−12n(n−1), in which q∈(0,1) is fixed. Hence, the divergence is much stronger, and one has to introduce alternative Borel and Laplace transforms to make sense of these formal series. We will discuss exponentially-improved asymptotics for the basic hypergeometric function 2ϕ0 and for solutions of the q-difference first Painlevé equation qPI. These are optimal truncated expansions, and re-expansions in terms of new q-hyperterminant functions. The re-expansions do incorporate the Stokes phenomena.
ISSN:0019-3577
DOI:10.1016/j.indag.2025.02.002