Wilson Loops and Minimal Surfaces
Nadav Drukker, David J. Gross, Hirosi Ooguri
TL;DR
The paper tests the AdS/CFT proposal by relating Wilson loops in N=4 SYM to minimal surfaces in AdS5×S^5 and by deriving the loop equation in both bosonic and supersymmetric settings. It shows that for a class of BPS loops, the area diverges but a Legendre transform yields a finite effective action that respects the loop equation; it analyzes boundary conditions, zig-zag symmetry, and the role of cusps and intersections. It then assesses how minimal-surface computations in AdS5×S^5 reproduce loop-equation predictions, finding agreement for smooth loops and nontrivial cusp contributions, with non-BPS loops requiring excited-string states and remaining challenging. Overall, the work provides substantial evidence for the Wilson loop – minimal surface correspondence while highlighting outstanding issues for general, non-BPS loops.
Abstract
The AdS/CFT correspondence suggests that the Wilson loop of the large N gauge theory with N=4 supersymmetry in 4 dimensions is described by a minimal surface in AdS_5 x S^5. We examine various aspects of this proposal, comparing gauge theory expectations with computations of minimal surfaces. There is a distinguished class of loops, which we call BPS loops, whose expectation values are free from ultra-violet divergence. We formulate the loop equation for such loops. To the extent that we have checked, the minimal surface in AdS_5 x S^5 gives a solution of the equation. We also discuss the zig-zag symmetry of the loop operator. In the N=4 gauge theory, we expect the zig-zag symmetry to hold when the loop does not couple the scalar fields in the supermultiplet. We will show how this is realized for the minimal surface.
