We study some aspects of Maldacena's large N correspondence between N = 4 superconformal gauge theory on D3-brane and maximal supergravity on AdS 5 × S 5 by introducing macroscopic strings as heavy (anti)-quark probes. The macroscopic strings are semi-infinite Type IIB strings ending on D3-brane world-volume. We first study deformation and fluctuation of D3-brane when a macroscopic BPS string is attached. We find that both dynamics and boundary conditions agree with those for macroscopic string in anti-de Sitter supergravity. As a by-product we clarify how Polchinski's Dirichlet and Neumann open string boundary conditions arise dynamically. We then study non-BPS macroscopic string anti-string pair configuration as physical realization of heavy quark Wilson loop. We obtain QQ static potential from the supergravity side and find that the potential exhibits nonanalyticity of square-root branch cut in 't Hooft coupling parameter. We put forward the nonanalyticity as prediction for large-N gauge theory at strong 't Hooft coupling limit. By turning on Ramond-Ramond zero-form potential, we also study θ vacuum angle dependence of the static potential. We finally discuss possible dynamical realization of heavy N-prong string junction and of large-N loop equation via local electric field and string recoil thereof. Throughout comparisons of the AdS-CFT correspondence, we find crucial role played by 'geometric duality' between UV and IR scales on directions perpendicular to D3-brane and parallel ones, explaining how AdS 5 spacetime geometry emerges out of four-dimensional gauge theory at strong coupling.

We investigate the asymptotic symmetry algebra of (2+1)-dimensional higher spin, anti-de Sitter gravity. We use the formulation of the theory as a Chern-Simons gauge theory based on the higher spin algebra hs(1, 1). Expanding the gauge connection around asymptotically anti-de Sitter spacetime, we specify consistent boundary conditions on the higher spin gauge fields. We then study residual gauge transformation, the corresponding surface terms and their Poisson bracket algebra. We find that the asymptotic symmetry algebra is a nonlinearly realized W ∞ algebra with classical central charges. We discuss implications of our results to quantum gravity and to various situations in string theory.

Aspects of Image superconformal U(N) gauge theory are studied a t finite temperature. Utilizing dual description of large-N and strong coupling limit via Type IIB string theory compactification on Schwarzschild-anti-de Sitter space-time, we study correlations of Wilson-Polyakov loops and heavy quark potential thereof. We find that the heavy quark potential is Coulomb-like and has a finite range, as expected for gauge theory in high temperature, deconfinement phase. The potential exhibits finite temperature scaling consistent with underlying conformal invariance. We also study isolated heavy quark on a probe D3-brane world-volume and find supporting evidence that near extremal D3-branes are located at the Schwarzschild horizon

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