arXiv subjects

Maximilian Schwick

Publications and source records attributed to Maximilian Schwick.

9 recordsLinked to original sources

arXiv2026

Andreev reflections and optimal truncation in the unitary Fermi droplet

We study the unitary Fermi gas in an external trap in the double-scaling limit of large flavor number N and large charge Q at fixed Q/N. At leading order, the problem reduces to the spectral zeta function of a BdG operator in an inhomogeneous pairing background. The grand potential admits a gradient expansion with distinct bulk and edge sectors. We show that when the trap is harmonic, the bulk sector expansion terminates: beyond the first three terms every bulk contribution integrates to zero. This cancellation is general and follows from zeros of the Euler beta function computed in the Son-Wingate effective field theory, independent of the low-energy constants. The truncation persists for anisotropic traps in any odd dimension. All higher-order dependence for harmonic potentials is therefore carried by the droplet edge. For anharmonic traps, the asymptotic bulk series is factorially divergent. Using a heat-kernel WKB analysis, we show that its large-order growth, sign oscillations, and optimal truncation are fixed by complex periodic orbits of the BdG problem, which are analytic continuations of Andreev reflections. We numerically confirm the predicted Borel singularities for quartic and sextic traps.

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arXiv2026

Large N instantons, BPS states, and the replica limit

We study the relation between large N instantons and conventional instantons, focusing on matrix models and topological strings. We show that the resurgent properties of the perturbative series at fixed but arbitrary N, including the replica limit N = 0, can be obtained from large N instantons. In the case of topological strings, it has been conjectured that the resurgent structure encoded by large N instantons is closely related to the spectrum of BPS states. We give direct evidence for this connection in the case of Seiberg-Witten theory and other topological string models, and we show in detail how the resurgent properties at fixed N follow from the large N theory, and therefore can be used to obtain information on BPS invariants.

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arXiv2026

A toy model for the quark pole mass

We study the pole mass for a heavy quark probe in the Gross--Neveu model, at the first non-trivial order in the $1/N$ expansion. We show that this mass suffers from a perturbative renormalon ambiguity structurally similar to the one in QCD. The exact large $N$ solution leads however to an explicit expression for the pole mass which can be decoded as a trans-series, and we find that non-perturbative corrections cure the renormalon ambiguity. We also calculate the self-energy of the heavy quark beyond perturbation theory by using the OPE method with condensates, and show that the results are in agreement with the large $N$ solution. The non-perturbative corrections to the pole mass turn out to be determined to a large extent by the condensate corrections to the self-energy. However, there is a class of corrections that has to be reorganized due to on-shell effects and cannot be obtained from the conventional condensate expansion. We discuss possible implications of this toy model for QCD.

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arXiv2026

Resurgence in the Virasoro Minimal String and 3d Gravity

We compute non-perturbative, resurgent contributions to the Virasoro minimal string and 3d gravity using techniques from hermitian matrix models. In particular, we construct a fully non-perturbative partition function for the Virasoro minimal string in terms of a Zak transform. In this context, negative tension D-branes appear naturally, which in the matrix model correspond to anti-eigenvalues, or instantons on the involuted sheet of the spectral curve. We further extend this analysis to resolvents and observe resurgent wall crossing phenomena between ZZ- and FZZT-branes. Using recent results that relate the Virasoro minimal string to 3d gravity with end-of-the-world branes we proceed to study the resurgent consequences of summing over the genus in 3d gravity, where we find non-perturbative contributions of doubly exponential type. These statements are then tested using resurgent large-order asymptotics. Lastly, we compute the non-perturbative eigenvalue density for generic hermitian matrix models and identify the change of asymptotic behavior at the edge of the eigenvalue distribution with a Stokes transition. This allows us to identify oscillations in the eigenvalue density with anti-Stokes behavior of FZZT-branes. In the case of 3d gravity with end-of-the-world branes we comment how this Stokes transition coincides with the onset of black hole behaviour and compute the non-perturbative primary density. Furthermore, we apply these techniques to the eigenvalue density of JT gravity to compute higher genus corrections.

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arXiv2026

New Instantons for Matrix Models

The complete, nonperturbative content of random matrix models is described by resurgent-transseries -- general solutions to their corresponding string-equations. These transseries include exponentially-suppressed multi-instanton amplitudes obtained by eigenvalue tunneling, but they also contain exponentially-enhanced and mixed instanton-like sectors with no known matrix model interpretation. This work shows how these sectors can be also described by eigenvalue tunneling in matrix models -- but on the non-physical sheet of the spectral curve describing their large-N limit. This picture further explains the full resurgence of random matrices via analysis of all possible eigenvalue integration-contours. How to calculate these "anti" eigenvalue-tunneling amplitudes is explained in detail and in various examples, such as the cubic and quartic matrix models, and their double-scaling limit to Painleve I. This further provides direct matrix-model derivations of their resurgent Stokes data, which were recently obtained by different techniques.

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arXiv2026

Non-Perturbative Real Topological Strings

We study the resurgent structure of Walcher's real topological string on general Calabi-Yau manifolds. We find trans-series solutions to the corresponding holomorphic anomaly equations, at all orders in the string coupling constant, by extending the operator formalism of the closed topological string, and we obtain explicit formulae for multi-instanton amplitudes. We find that the integer invariants counting disks appear as Stokes constants in the resurgent structure, and we provide experimental evidence for our results in the case of the real topological string on local $\mathbb{P}^2$.

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arXiv2026

All the D-Branes of Resurgence

It was recently shown how to account for all instantons of hermitian matrix models via (anti-) eigenvalue-tunneling -- including both exponentially-suppressed and exponentially-enhanced transseries-transmonomials which are predicted by resurgence. Matrix-model eigenvalue-tunneling corresponds to ZZ-branes. The present work shows how matrix-model anti-eigenvalues correspond to negative-tension ZZ-branes; and how to compute generic nonperturbative sectors -- with both ZZ and negative-tension-ZZ branes -- in the minimal-string free-energy. Negative-tension D-branes are herein a requirement of resurgence. This results in the construction of minimal-string free-energy transseries and the analytic computation of their resurgent Stokes data. Calculations are presented via Liouville boundary conformal field theory and via (matching) matrix model analysis. Minimal-string results are extended to Jackiw-Teitelboim gravity. Building on the matrix model analysis, one extension towards topological string theory is obtained via the remodeling-conjecture -- which allows for addressing one-cut, toric Calabi-Yau geometries. Building on the Liouville theory calculation, one other extension towards critical string theory is obtained via the H3+ - Liouville correspondence -- which allows for addressing negative-tension D-instantons in AdS spacetime. Throughout, checks of the construction and formulae are made in several examples, against both Borel resurgent analysis and string-equation transseries data.

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arXiv2026

Exact Solutions to Matrix Models and String Theories: The Local Construction

Exact nonperturbative solutions to hermitian one-matrix models, their topological string duals, as well as their double-scaling limits to multicritical and minimal string theories, may be obtained via the use of resurgent transseries. These solutions are generically resonant, entailing both eigenvalues and anti-eigenvalues, or, equivalently, both D-branes and negative-tension D-branes -- but are otherwise intricate to write down, having been previously addressed on a case-by-case approach. This work shows how there is a general and rather compact way to write down all these exact and fully nonperturbative transseries solutions in closed-form, immediately starting from the spectral geometry of the matrix model or string theory at hand, in the form of a discrete Fourier or Zak transform for their partition functions. This structure is inherently associated to the existence of anti-eigenvalues or negative-tension D-branes. The validity of these solutions is testable across all values of the parameters -- from weak to strong 't Hooft coupling, from small to large N; equivalently, from semi-classical to deeply quantum regimes -- and many such nonperturbative tests are performed against diverse examples ranging from matrix models to non-critical strings, fully validating our analytical and exact expressions. In particular, anti-eigenvalues or negative-tension D-branes are absolutely required to find sharp numerical matches. In order to study these solutions globally across their phase diagrams, however, complete non-linear Stokes data is still needed -- which will be addressed in a complementary follow-up paper.

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arXiv2022

Resurgent Stokes Data for Painleve Equations and Two-Dimensional Quantum (Super) Gravity

Resurgent-transseries solutions to Painleve equations may be recursively constructed out of these nonlinear differential-equations -- but require Stokes data to be globally defined over the complex plane. Stokes data explicitly construct connection-formulae which describe the nonlinear Stokes phenomena associated to these solutions, via implementation of Stokes transitions acting on the transseries. Nonlinear resurgent Stokes data lack, however, a first-principle computational approach, hence are hard to determine generically. In the Painleve I and Painleve II contexts, nonlinear Stokes data get further hindered as these equations are resonant, with non-trivial consequences for the interconnections between transseries sectors, bridge equations, and associated Stokes coefficients. In parallel to this, the Painleve I and Painleve II equations are string-equations for two-dimensional quantum (super) gravity and minimal string theories, where Stokes data have natural ZZ-brane interpretations. This work computes for the first time the complete, analytical, resurgent Stokes data for the first two Painleve equations, alongside their quantum gravity or minimal string incarnations. The method developed herein, dubbed "closed-form asymptotics", makes sole use of resurgent large-order asymptotics of transseries solutions -- alongside a careful analysis of the role resonance plays. Given its generality, it may be applicable to other distinct (nonlinear, resonant) problems. Results for analytical Stokes coefficients have natural structures, which are described, and extensive high-precision numerical tests corroborate all analytical predictions. Connection-formulae are explicitly constructed, with rather simple and compact final results encoding the full Stokes data, and further allowing for exact monodromy checks -- hence for an analytical proof of our results.

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