This is a compact review of recent results on supersymmetric Wilson loops in ABJ(M) and related theories. It aims to be a quick introduction to the state of the art in the field and a discussion of open problems. It is divided into short chapters devoted to different questions and techniques. Some new results, perspectives and speculations are also presented. We hope this might serve as a baseline for further studies of this topic. Prepared for submission to J. Phys. A.

The 6d N = (2, 0) theory has natural surface operator observables, which are akin in many ways to Wilson loops in gauge theories. We propose a definition of a 'locally BPS' surface operator and study its conformal anomalies, the analog of the conformal dimension of local operators. We study the abelian theory and the holographic dual of the large N theory refining previously used techniques. Introducing non-constant couplings to the scalar fields allows for an extra anomaly coefficient, which we find in both cases to be related to one of the geometrical anomaly coefficients, suggesting a general relation due to supersymmetry. We also comment on surfaces with conical singularities.

Consistency of the unconventional view of de Sitter space as a quantum theory of gravity with a finite number of degrees of freedom requires that Coleman-De Luccia tunneling rates to vacua with negative cosmological constant should be interpreted as recurrences to low-entropy states.This demand translates into two constraints, or consistency conditions, on the scalar potential that are generically as follows: 1) the distance in field space between the de Sitter vacuum and any other vacuum with negative cosmological constant must be of the order of the reduced Planck mass or larger and 2) the fourth root of the vacuum energy density of the de Sitter vacuum must be smaller than the fourth root of the typical scale of the scalar potential. These consistency conditions shed a different light on both outstanding hierarchy problems of the Standard Model of particle physics: the scale of electroweak symmetry breaking and the scale of the cosmological constant. Beyond the unconventional interpretation of quantum de Sitter space, we complete the analytic understanding of the thin-wall approximation of Coleman-De Luccia tunneling, extend its numerical analysis to generic potentials and discuss the role of gravity in stabilizing the Standard Model potential.

We study possible geometries and R-symmetry breaking patterns that lead to globally BPS surface operators in the six dimensional N = ( 2 , 0 ) theory. We find four main classes of solutions in different subspaces of R 6 and a multitude of subclasses and specific examples. We prove that these constructions lead to supersymmetry preserving observables and count the number of preserved supercharges. We discuss the underlying geometry, calculate their anomalies and present analogous structures for the holographic dual M2-branes in AdS 7 × S 4. We also comment on the dimensional reduction of these observables to line and surface operators in 4D and 5D theories. This rich spectrum of operators is proposed as the simplest and most natural observables of this mysterious theory.

Surface operators are among the most important observables of the 6d $$ \mathcal{N} $$ N = (2, 0) theory. Here we apply the tools of defect CFT to study local operator insertions into the 1/2-BPS plane. We first relate the 2-point function of the displacement operator to the expectation value of the bulk stress tensor and translate this relation into a constraint on the anomaly coefficients associated with the defect. Secondly, we study the defect operator expansion of the stress tensor multiplet and identify several new operators of the defect CFT. Technical results derived along the way include the explicit supersymmetry tranformations of the stress tensor multiplet and the classification of unitary representations of the superconformal algebra preserved by the defect.