3 papers
math.NT2021
On the positive powers of -analogs of Euler series
Changgui Zhang
The most simple and famous divergent power series coming from ODE may be the so-called Euler series , that, as well as all its positive powers, is…
math.DS2020
On the vanishing of coefficients of the powers of a theta function
Jacques Sauloy, Changgui Zhang
A result on the Galois theory of -difference equations \cite{JSTALPAEN} leads to the following question: if $q \in \Cs$, $\lmod q \rmod < 1$ and if one sets $\thq(z) := \sum\lim…
math.CV2011
La série entière possède une frontière naturelle~!
Changgui Zhang
The lacunary series are the most classical examples among all the power series whose circle of convergence constitutes a natural boundary (\cite[§~93-94, p.~372-383]{Di}, \cite[§7.…