In index notation, does the term $σ_{ik}x_{j}n_{k}$ mean $\bf{σx}\cdot\bf{n}$ or $\bf{xσ}\cdot\bf{n}$? Here $σ$ is a second-order tensor and $x,n$ are vectors.
On the same note, is $$\frac{\partialσ_{ik}}{\partial x_{k}}x_{j}$$ equivalent to $\nabla(\bf{xσ})$ or $\nabla(\bf{σx})$? For some reason there is an index notation rule that eludes me.
Pardon me for the fundamendality or even stupidity of my questions! Long time lurker, first time poster.