Variational methods in general relativity
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Variational methods in general relativity refers to various mathematical techniques that employ the use of variational calculus in Einstein's theory of general relativity. The most commonly used tools are Lagrangians and Hamiltonians and are used to derive the Einstein field equations.
[edit] Lagrangian methods
Main article: Einstein-Hilbert action
The equations of motion in known physical theories can be derived from an object called the Lagrangian. In classical mechanics, this object is usually of the form, 'kinetic energy - potential energy'.
See also Palatini action, Plebanski action, MacDowell-Mansouri action, Friedel-Starodubtsev action