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Introduction to 1-summability and resurgence

4 Pith papers cite this work. Polarity classification is still indexing.

4 Pith papers citing it
abstract

This text is about the mathematical use of certain divergent power series. The first part is an introduction to 1-summability. The definitions rely on the formal Borel transform and the Laplace transform along an arbitrary direction of the complex plane. Given an arc of directions, if a power series is 1-summable in that arc, then one can attach to it a Borel-Laplace sum, i.e. a holomorphic function defined in a large enough sector and asymptotic to that power series in Gevrey sense. The second part is an introduction to Ecalle's resurgence theory. A power series is said to be resurgent when its Borel transform is convergent and has good analytic continuation properties: there may be singularities but they must be isolated. The analysis of these singularities, through the so-called alien calculus, allows one to compare the various Borel-Laplace sums attached to the same resurgent 1-summable series.In the context of analytic difference-or-differential equations, this sheds light on the Stokes phenomenon. A few elementary or classical examples are given a thorough treatment (the Euler series, the Stirling series, a less known example by Poincar\'e). Special attention is devoted to non-linear operations: 1-summable series as well as resurgent series are shown to form algebras which are stable by composition. As an application, the resurgent approach to the classification of tangent-to-identity germs of holomorphic diffeomorphisms in the simplest case is included. An example of a class of non-linear differential equations giving rise to resurgent solutions is also presented. The exposition is as self-contained as can be, requiring only some familiarity with holomorphic functions of one complex variable.

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2026 2 2025 2

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UNVERDICTED 4

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representative citing papers

Higher-Rank Mathieu Opers, Toda Chain, and Analytic Langlands Correspondence

math-ph · 2025-12-21 · unverdicted · novelty 8.0

Constructs solutions to higher-rank oper Riemann-Hilbert problems via a single non-linear integral equation, proving that the oper generating function equals the Toda Yang-Yang function and thereby establishing the Nekrasov-Rosly-Shatashvili conjecture.

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