I am looking for a vector expression for the curl of a composite vector-valued function. In other words
$$
\nabla\times\mathbf{A}(\mathbf{B}) = ?
$$
In indicial notation, this can be written as
$$
\left(\nabla\times\mathbf{A}(\mathbf{B})\right)_i = -\epsilon_{ijk}\left(\frac{\partial A_k}{\partial B_n}\right)\frac{\partial B_n}{\partial x_j}
$$
where $\epsilon_{ijk}$ is the Levi-Civita symbol and Einstein summation is used. so far, the simplest expression we could write was
$$
\left(\nabla\times\mathbf{A}(\mathbf{B})\right)_i = \epsilon_{ijk}\left[\left(\frac{\partial\mathbf{A}}{\partial\mathbf{B}}\right)\cdot\left(\nabla\otimes\mathbf{B}\right)^T\right]_{jk}
$$
where $\cdot$ is used to denote the usual matrix product and $\otimes$ the Kronecker outer product. Could this be written all in vector notation?
2026-04-18 07:39:31.1776497971