Instanton contributions to the ABJM free energy from quantum M2 branes

Abstract

Abstract We present a quantum M2 brane computation of the instanton prefactor in the leading non-perturbative contribution to the ABJM 3-sphere free energy at large N and fixed level k. Using supersymmetric localization, such instanton contribution was found earlier to take the form $$ {F}^{inst}\left(N,k\right)=-{\left({\sin}^2\frac{2\pi }{k}\right)}^{-1}\exp \left(-2\pi \sqrt{\frac{2N}{k}}\right)+.\dots $$ F inst N k = − sin 2 2 π k − 1 exp − 2 π 2 N k + . … The exponent comes from the action of an M2 brane instanton wrapped on S3/ℤk, which represents the M-theory uplift of the ℂP1 instanton in type IIA string theory on AdS4 × ℂP3. The IIA string computation of the leading large k term in the instanton prefactor was recently performed in arXiv:2304.12340. Here we find that the exact value of the prefactor $$ {\left({\sin}^2\frac{2\pi }{k}\right)}^{-1} $$ sin 2 2 π k − 1 is reproduced by the 1-loop term in the M2 brane partition function expanded near the S3/ℤk instanton configuration. As in the Wilson loop example in arXiv:2303.15207, the quantum M2 brane computation is well defined and produces a finite result in exact agreement with localization.