Nekrasov prepotential with fundamental matter from the quantum spin chain
Yegor Zenkevich
TL;DR
This work tests the Nekrasov–Seiberg correspondence for $SU(N_c)$ gauge theories with $N_f$ fundamental hypermultiplets by solving the Baxter equation of the XXX spin chain and comparing quantum deformed Seiberg–Witten periods to the Nekrasov prepotential. The authors derive a perturbative solution in $\hbar$, construct a differential operator $\hat{\mathcal{O}}$ that maps classical periods to their quantum-corrected counterparts, and validate the matching of $A$- and $B$-periods against $\mathcal{F}_{Nek}$ up to $O(\hbar^2)$ and $\Lambda^{2N_c-N_f}$, including explicit one-instanton checks in several cases. They also compute the exact one-loop prepotential for $SU(2)$ with up to four hypermultiplets, showing that the B-periods are invariant under different placements of masses between the Baxter equation's two exponential terms and agree with perturbative Nekrasov results to all orders in $\hbar$. Together, these results support the quantum–integrable systems interpretation of the Nekrasov prepotential in the presence of fundamental matter and encourage further generalization beyond the cases studied. The approach offers a concrete bridge between spin-chain Baxter equations and the Seiberg–Witten framework, with potential implications for the AGT correspondence and exact quantization.
Abstract
Nekrasov functions were conjectured in \cite{Mironov:2009uv} to be related to exact Bohr-Sommerfeld periods of quantum integrable systems. This statement was thoroughly checked for the case of the pure $SU(N_c)$ gauge theory in \cite{Mironov:2009dv} and \cite{Popolitov:2010bz}. Here we successfully perform a set of checks in the case of gauge group $SU(N_c)$ with additional $N_f$ fundamental hypermultiplets. We show that the Baxter equation for the spin chain gives the same quantum periods as the one for the Gaudin system in this case.
