English

Exponentially-improved asymptotics for $q$-difference equations: ${}_2\phi_0$ and $q{\rm P}_{\rm I}$

Classical Analysis and ODEs 2024-03-05 v1

Abstract

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 qq-world the nnth coefficient is often of the size q12n(n1)q^{-\frac12 n(n-1)}, in which q(0,1)q\in(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{}_2\phi_0 and for solutions of the qq-difference first Painlev\'e equation qPIq{\rm P}_{\rm I}. These are optimal truncated expansions, and re-expansions in terms of new qq-hyperterminant functions. The re-expansions do incorporate the Stokes phenomena.

Keywords

Cite

@article{arxiv.2403.02196,
  title  = {Exponentially-improved asymptotics for $q$-difference equations: ${}_2\phi_0$ and $q{\rm P}_{\rm I}$},
  author = {Nalini Joshi and Adri Olde Daalhuis},
  journal= {arXiv preprint arXiv:2403.02196},
  year   = {2024}
}

Comments

15 pages, 1 figure

R2 v1 2026-06-28T15:08:36.465Z