This more general approach allows for a more natural coordinate-free approach to integration on manifolds.
2.
Where d denotes the exterior derivative a natural coordinate-and metric-independent differential operator acting on forms, and the ( dual ) Hodge star operator \ star is a linear transformation from the space of 2-forms to the space of ( 4 " 2 )-forms defined by the metric in Minkowski space ( in four dimensions even by any metric conformal to this metric ).
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