Define an expression like:
$\chi\,=\,C_{p1}\,\left[ h\,e^{- i\,p1.\,x}\,\, +\,\,h^{\dagger}\,e^{+i\,p1\,.\,x}\right]$
where $p1$ and $x$ are four-vectors; $C_{p1} = \ \frac{1}{\sqrt{(2 \pi)^3} \sqrt{2 \omega\,(p1,\ m)}}$, and $x\ .\ p1\ =\omega(p_1,m)\,t\ - {\vec p1} {\vec x}$
How does one teach Mathematica to do things like $\chi \cdot \chi\,$, $\nabla \chi $, $\partial_{t}\ \chi$ etc. but not have to explicitly have to type the full form of the four vectors - in the subsequent input and results of evaluations?
