Equation Icon  a i a (0)i (1) a (1)i 2 gμν(t,x ;a ) = gμν(t,x ;a ) + 𝜀gμν(t,x ;a ) + O(𝜀 ) (22.3 ) (n) a i (n) a (0)i hμν (t,x ;a ) = h μν (t,x ;a ) + O (𝜀), (22.4 )