Example image of eyePlorer eyePlorer map for 'Gravitational instanton': Complete metric space Differential geometry Einstein field equations Mathematical physics Riemannian manifold Vacuum Instanton Quantum gravity Yang–Mills theory Euclidean space Riemann curvature tensor Einstein manifold Hyperkähler manifold Pseudo-Riemannian manifold Cosmological constant Twistor theory Kähler manifold 3-sphere Euler angles Cyclic group SO(4) Subgroup Coordinate system Calabi–Yau manifold Orbifold String theory Stephen Hawking Peter B. Kronheimer Nuts and bolts (general relativity)