I am trying to parse this expression:
$(\nabla_{\nabla p \times e_1} \nabla p) \times \nabla p$
The setup is that $p$ is a polynomial in $\mathbb{R}[x,y,z]$ and $e_1 = (1,0,0)$ is one of the standard basis vectors for $\mathbb{R}^3$. The part I haven't encountered before is the notation $\nabla_g f$ so I would like to know what that means. Thank you!
