String instanton in AdS(4)xCP(3)
Alessandra Cagnazzo, Dmitri Sorokin, Linus Wulff
TL;DR
This work analyzes a string instanton in the AdS$_4\times$CP$^3$ background, focusing on a worldsheet wrapping a nontrivial CP$^1$ inside CP$^3$. By reducing the Green–Schwarz action to quadratic order in fermions and performing a careful kappa-symmetry gauge fixing, the authors derive the fermionic equations of motion on the instanton and count the zero modes. They find exactly $12$ fermionic zero modes, split into eight massive and four massless-like modes, all tied to the background supersymmetries and the monopole structure on the worldsheet, establishing the instanton as 1/2 BPS. The results imply potential non-perturbative corrections to the worldsheet dynamics and offer a bridge to M-theory via the Euclidean M2-brane counterpart, with implications for ABJM/ABJ generalizations and the AdS$_4$/CFT$_3$ correspondence.
Abstract
We study the string instanton wrapping a non-trivial two-cycle in CP(3) of the type IIA string theory compactified on AdS_4 x CP(3) superspace and find that it has twelve fermionic zero modes associated with 1/2 of the supersymmetry of the background thus manifesting that this classical instanton configuration is 1/2 BPS
