Macroscopic Strings as Heavy Quarks of Large N Gauge Theory and Anti-de Sitter Supergravity

We study several aspects of Maldacena's proposed correspondence between N=4 superconformal gauge theory on D3-brane and supergravity on $adS_5 \times S_5$ by introducing semi-infinite strings ending on D3-brane as heavy (anti)-quark probes. We first study deformation and fluctuation of D3-brane upon attaching a macroscopic BPS string. We find that both dynamics and boundary conditions agree with those for macroscopic string in $adS_5$. As a by-product we clarify emergence of Polchinski's Dirichlet and Neumann boundary conditions. We then study non-BPS string anti-string pair configuration as physical realization of heavy quark Wilson loop. We obtain $Q \bar Q$ static potential and again find agreements between gauge theory and supergravity results. By turning on Ramond-Ramond zero-form potential, we also study $\theta$-dependence of the static potential. We finally discuss dynamical realization of loop equation via turning on local electric field and recoil of heavy quark thereof, and of heavy baryon via of N-prong string junction. We emphasize crucial role played by `geometric duality' between coordinates perpendicular to D3-brane and parallel ones, hinting a possible explanation of emergence of entire $adS_5$ spacetime.