Equation Icon  dim∑ 𝔥−1 (dim∑ 𝔥−1 ) (dim∑𝔥− 1 ) G μν ∂β μ(t)∂β ν(t) = ∂ βi(t) ∂βi(t) − ∂βi(t) ∂βj (t) + ∂φ(t)∂φ (t). (9.88 ) i=1 i=1 j=1