Emil Hakan Leeb-Lundberg

arXiv2026

Hyperfunctions in $A$-model Localization

We apply localization techniques to topologically $A$-twisted $\mathcal{N}=(2,2)$ supersymmetric theories of vector and chiral multiplets on $S^{2}$ and derive a novel exact formula for abelian observables, described by a distribution integrated along the real line. The distributional integral formula is verified by evaluating the correlator of the $A$-twisted $\mathbb{CP}^{N-1}$ gauged linear sigma model and confirming the standard selection rule. Finally, we use hyperfunctions to demonstrate the equivalence between the distributional and complex contour integral descriptions of the $\mathbb{CP}^{N-1}$ correlator, and find agreement with the Jeffrey-Kirwan residue prescription.

hep-th↗

arXiv2025

Unstable Instantons in A-model Localization

We apply localization techniques to $A$-twisted $\mathcal{N}=(2,2)$ theories of vector multiplets on $S^{2}$. We derive formulae for $A$-model partition functions and correlators as integrals along a real contour, as opposed to a complex one. Using the correlator formula, we successfully recover the unstable instanton partition function of pure two-dimensional Yang-Mills theory from the vacuum expectation value of an $A$-model operator.

hep-th↗