Penrose's weak cosmic censorship conjecture

Let $(\mathcal{M},g)$ be a $3+1$-dimensional Lorentzian spacetime solving the Einstein field equations, arising as the maximal future development of generic, regular, asymptotically flat initial data. A future null infinity is complete when its null generators have infinite affine length. Weak cosmic censorship conjecture. The maximal future development possesses a complete future null infinity. This conjecture asserts that singularities arising from generic regular asymptotically flat data are hidden from distant observers; its resolution remains open in general, although important results are known in symmetry-reduced and other special settings.