In the general theory of relativity, what is the term for a boundary in spacetime beyond which events cannot affect the observer?
Event horizon to cover the horizon and thermalize into a Planck length-thick membrane. A complete description of event horizons is expected to, at minimum, require a theory of quantum gravity. One such candidate theory is M-theory. Another such candidate theory is loop quantum gravity. Event horizon In general relativity, an event horizon (EH) is a region in spacetime beyond which events cannot affect an outside observer. In layman's terms, it is defined as the shell of "points of no return", i.e., the boundary at which the gravitational pull of a massive object becomes so great as to make escape impossible. An event
Gibbons–Hawking–York boundary term elegantly in the quantum context the complete identification between spacetime geometry and dynamical fields. Gibbons–Hawking–York boundary term In general relativity, the Gibbons–Hawking–York boundary term is a term that needs to be added to the Einstein–Hilbert action when the underlying spacetime manifold has a boundary. The Einstein–Hilbert action is the basis for the most elementary variational principle from which the field equations of general relativity can be defined. However, the use of the Einstein–Hilbert action is appropriate only when the underlying spacetime manifold formula_1 is closed, i.e., a manifold which is both compact and without boundary. In the event that the