As explained in Weinberg's *The Quantum Theory of Fields, Volume 2, Chapter 20.7 Renormalons*, instantons are a known source of poles in the Borel transform of the perturbative series. These poles are on the negative real axis, and the series remains Borel-summable as long as the coupling constant is not too large.

However, instantons are objects in the *Euclidean* version of QFT. What's the significance of the above Borel resummation in the Minkowski theory?

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