text: Hermann Weyl added a local symmetry to this theory in his attempt to unify it with electromagnetism.
full_question: Hermann Weyl added a local symmetry to this theory in his attempt to unify it with electromagnetism. Cyclic permutations of the indices of one construct defined by this theory must sum to zero according to a result of an Italian mathematician. Hilbert derived the central equation of this theory by requiring the action be invariant under coordinate transformations. That equation from this theory quantifies curvature with a rank two tensor an includes source terms from momentum and energy density in four dimensional spacetime. For 10 points name this theory of gravity developed by Einstein.
first_sentence: Hermann Weyl added a local symmetry to this theory in his attempt to unify it with electromagnetism.