wishIwasSalludon
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The Einstein–Hilbert action in general relativity is the action that yields the Einstein field equationsthrough the stationary-action principle. With the (− + + +) metric signature, the gravitational part of the action is given as[1]
where
is the determinant of the metric tensor matrix,
is the Ricci scalar, and
is the Einstein gravitational constant (
is the gravitational constant and
is the speed of light in vacuum). If it converges, the integral is taken over the whole spacetime. If it does not converge,
is no longer well-defined, but a modified definition where one integrates over arbitrarily large, relatively compact domains, still yields the Einstein equation as the Euler–Lagrange equation of the Einstein–Hilbert action. The action was proposed[2] by David Hilbert in 1915 as part of his application of the variational principle to a combination of gravity and electromagnetism.[3]: 119
where