$$ \gdef\pd#1#2{\frac{\partial #1}{\partial #2}} \gdef\d#1{\, \mathrm{d}#1} \gdef\dx{\d{x}} \gdef\tr#1{\operatorname{tr} (#1)} $$ $$ \gdef\norm#1{\left \lVert #1 \right\rVert} \gdef\seminorm#1{| #1 |} $$ $$ \gdef\vec#1{\mathbf{\boldsymbol{#1}}} \gdef\dvec#1{\bar{\vec #1}} $$