BTZ black hole, geodesics, and CFT thermal correlators
S_EE = — | G(0,x): —
AdS₃/CFT₂: BTZ black hole ↔ thermal state of 2D CFT. Holographic entanglement entropy: S = (c/3)·log(sinh(πTx)/πTa) (Ryu-Takayanagi). Thermal Green's function: G(t,x) = (πT/sinh(πT√(x²-t²)))^{2Δ}. Bulk geodesics in the Poincaré disk compute boundary correlators. Left: AdS₃ Poincaré disk with geodesics anchored at boundary points. Right: CFT correlator G(x) at t=0.