Comass
= Comass
{title2=$\|\varphi_x\|_*=\sup_{\xi\text{ oriented unit simple }p\text{-vector}}|\varphi_x(\xi)|$}
The comass is the operator norm of a differential form restricted to simple unit tangent multivectors. Reversing orientation gives the equivalent two-sided bound. It differs from the Euclidean norm of all the form's components. The <calibration> bound uses comass because tangent planes are represented by simple multivectors.