Global symmetry

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In physics, a global symmetry is a symmetry that holds at all points in the spacetime under consideration, as opposed to a local symmetry which varies from point to point.

Global symmetries require conservation laws, but not forces, in physics.

An example of a global symmetry is the action of the (for a constant - making it a global transformation) group on the Dirac Lagrangian:

Under this transformation the wavefunction changes as and and so:

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