Insane Anti-Membranes?

TL;DR

The paper investigates the backreaction of fully localized anti--M2 branes on the Taub-NUT-type $A_8$ background, aiming to determine whether flux singularities are tied to AdS-like UV conditions or to brane smearing. Using the Borokhov–Gubser first-order formalism, the authors map the complete space of linear deformations around the BPS $A_8$ solution and identify the unique deformation corresponding to anti--M2 backreaction via IR/UV matching. They find that the resulting backreacted solution exhibits IR and flux-related singularities that cannot be attributed to the anti--M2 sources themselves or to smearing, and these pathologies persist despite the non-AdS UV asymptotics. The work strengthens the view that backreaction problems of anti-branes are robust to changes in UV boundary conditions and smearing and has implications for the viability of metastable states and microstate constructions in eleven-dimensional supergravity.

Abstract

The backreactions of anti-branes on a variety of supergravity backgrounds have been shown in a recent series of papers to be riled by some unexplained flux singularities. All of the situations studied so far involve backgrounds with (close to) AdS-asymptotics. It is the purpose of this work to study the backreaction of anti-M2 branes on a background exhibiting a different UV behavior: The so-called $\mathbb{A}_8$ regular solution of eleven-dimensional supergravity that we consider has "Taub-NUT type" asymptotics. As it turns out, some subleading infrared singularities are inevitable; they cannot be naturally ascribed to the anti-branes backreacting on this background. Moreover, our configuration does not involve smeared branes. This lends further credence to the work of Bena et al. suggesting that the singularities encountered are in no way remnants of smearing that would wash away once brane polarization is taken into account.