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Critical Points at Infinity, Non-Gaussian Saddles, and Bions

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

4 Pith papers citing it
abstract

It has been argued that many non-perturbative phenomena in quantum mechanics (QM) and quantum field theory (QFT) are determined by complex field configurations, and that these contributions should be understood in terms of of Picard-Lefschetz theory. In this work we compute the contribution from non-BPS multi-instanton configurations, such as instanton-anti-instanton $[{I}\bar{I}]$ pairs, and argue that these contributions should be interpreted as exact critical points at infinity. The Lefschetz thimbles associated with such critical points have a specific structure arising from the presence of non-Gaussian, quasi-zero mode (QZM), directions. When fermion degrees of freedom are present, as in supersymmetric theories, the effective bosonic potential can be written as the sum of a classical and a quantum potential. We show that in this case the semi-classical contribution of the critical point at infinity vanishes, but there is a non-trivial contribution that arises from its associated non-Gaussian QZM-thimble. This approach resolves several puzzles in the literature concerning the semi-classical contribution of correlated $[{I}\bar{I}]$ pairs. It has the surprising consequence that the configurations that dominate the expansion of observables, and the critical points that define the Lefschetz thimble decomposition need not be the same, a feature not present in the traditional Picard-Lefschetz approach.

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hep-th 4

years

2026 3 2024 1

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UNVERDICTED 4

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representative citing papers

Renormalons as Saddle Points

hep-th · 2024-10-09 · unverdicted · novelty 6.0

Renormalons can be understood as saddle points of the 1-loop effective action in toy models, enabled by the quantum scale anomaly.

The Double Well Done Doubly-Well

hep-th · 2026-06-03 · unverdicted · novelty 3.0

Presents explicit trans-series calculations for the double-well spectrum via exact WKB and path integral approaches up to four-instanton level.

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