= Scalar shear potential
{title2=$\chi=\frac{a^2}{\bar N}(\dot E-B)$}
For the negative <extrinsic curvature> convention and a <shift vector> entering the line element as $dx^i-N^i dt$, the trace-free scalar curvature perturbation is $\delta K^i{}_j{}_{\rm TF}=-(\partial^i\partial_j-\delta^i_j\Delta/3)\chi$. Here spatial raised derivatives use $a^{-2}\delta^{ij}$, so $\Delta=a^{-2}\nabla^2$. Changing the sign of the metric <shift vector> changes the corresponding definition of $\chi$.
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