Some basic Mathematica info, mostly to stop myself having to continually research things that I should already know. Basic syntax to start.

(*comment*) code comments should be between (*
“string”a string is defined by quotation marks.
a is an assignment.
2*10^5 standard form (replaces the usual 2e5).
esc phi esc greek letter phi.
Sin[0] functions begin with a capital letter with their arguments in square brackets.
{x1, x2, x3} list of variables....

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Dalespam recently brought up an interesting semantic issue. What is the meaning of “relative” versus “absolute”? I did not have time to intervene in that thread but the subject links well with the musings of this Blog.

Obviously “relative” is what is defined “in relation with” or by comparison with another object, but in the context of Special Relativity this may mean three different things:

(a) That a measurement (of time or space) is made from and hence with regard...

[tex]R = \frac{\sigma(e^+ P^+ \rightarrow C)}{\sigma(e^+ P^+ \rightarrow \bar{\nu}_e)}[/tex]

We know the proton composition is UUD and the reaction is a scattering and not a decay. So the positron has to scatter off one of the constituent quarks in the proton to produce either a charm quark or a neutrino. We know that lepton number and presumably quark number have to be preserved at each vertex as well.

A Feynman diagram (dunno how to draw here) would be one of those vertical...