I rewrote the section *Fourier transform – Over Cartesian spaces*, now sticking with the convention that the factors of $2\pi$ all go into the volume form for the wave-vector integration (instead of in the exponentials). I hope I have changed everything consistently now…

Also polished and further expanded a little here and there. The I touched the Idea-sectin a little

]]>added more basic material, up to the statement that Fourier transform of distributions turns convolution into products (this prop.) and followed by the remark (here) that the converse formula, whenever it is well defined, may be taken as the *definition* of the product of distributions (this connecting to the beginning of the Idea-section there).

I have brought in some standard stuff to *Fourier transform* in a new section *Over Cartesian spaces*. (Superceding the previous section “On the real line”.)