Gibbons-Hawking-York boundary term

== English == === Etymology === The necessity of such a boundary term was first realised by James W. York and later refined in a minor way by Gary Gibbons and Stephen Hawking. === Proper noun === Gibbons-Hawking-York boundary term (physics) In general relativity, a term that needs to be added to the Einstein-Hilbert action when the underlying spacetime manifold has a boundary.