Equation Icon  (0) (1∕2) 1- (1) X = ξR , X AB = 4R δAB , X μν = ±R μν , 1 1 X (3A∕B2,)μν = -R δABg μν − -R μναβ(γαγβ )AB , 4 2 X (2) = 1R (g g + g g ) − R g − R g − R − R , (133 ) μν,αβ 2 μα νβ μβ να αμ βν βν αμ μανβ ναμβ