Equation Icon  ( ) 1 ( a′ b′ ) 1 cd′ 𝒯ab = --(1 − 2ξ) ga ∇a ′∇b + gb ∇a ∇b ′ + 2ξ − -- gabg ∇c∇d ′ 2 ( ) ( 2 ) ( ) a′ b′ c c′ 1- 1- 2 − ξ ∇a ∇b + ga gb ∇a ′∇b′ + ξgab ∇c ∇ + ∇c ′∇ + ξ Rab − 2gabR − 2m gab, (57 )