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”.)

I have created an entry-for-inclusion

in order to collect notation and terminology for plane (relativistic) waves (as a glorified “related concepts”-section); and so I am including this now into the relevant entries.

In the course of this I created stubs for *speed of light*, *Compton wavelength* and *dispersion relation* redirecting *energy-momentum relation*, but no substantial content yet in any of these stub entries.

I’ll go next and harmonize *Fourier transform* with this.

(Previously I had had the ambition there to stick with the convention where the “$2\pi$” is in the exponents, instead of in the global prefactors; but I feel now that this is just too different from established practice, and I’ll change it.)

]]>gave *wavelength* a bare minimum of content

needed to be able to point to *wave vector*, so I created a bare minimum entry

needed to be able to point to *plane wave*, so I created a bare minimum entry

I gave *Parseval”s theorem* a stub entry (in the course of bringing in substance into the entry *Fourier transform*)

I gave *Fourier inversion theorem* a stub entry (in the course of bringing in substance into the entry *Fourier transform*)

just so that hyperlinks work, I created stubs for *Fourier-Laplace transform* and also *Laplace transform*