Expert: Maria - 12/3/2006

Question
Hi Maria,

This is a very trivial question, but it keeps bugging me. There is a progressive rock group out of Mexico City, Mexico called Delta de Dirac.  So..."Change of...Dirac."  I can't find any word like "dirac" in Spanish, Portuguese, or even Latin.  I assume it probably is a reference to direction, since the band's style is a distinct departure from the urban Mexican scene, but even if so what is the derivation?  You can find them on garageband.com

Answer
Hello,

First of all I have to tell you that “Delta de Dirac”(or simply “Dirac”) has nothing to do with Latin.

In fact “Dirac” is the name of the British theoretical physicist Paul Dirac (1902-1984) who shared the Nobel Prize in physics for 1933 with Erwin Schrödinger, "for the discovery of new productive forms of atomic theory".

As for “Delta”, it is the name of the fourth letter of the ancient Greek alphabet which in this case is used to indicate an impulse function, since  the Dirac delta /Dirac's delta / the so-called "Dirac equation” in English, or “Delta de Dirac”  in Spanish, is referred to  the unit impulse function which "describes the behaviour of fermions and  led to the prediction of the existence of antimatter" just  introduced by Paul Dirac.
(See http://en.wikipedia.org/wiki/Dirac_equation).

Such an equation can usually be informally "thought of as a function δ(x) that has the value of infinity for x = 0, the value zero elsewhere".
(See http://en.wikipedia.org/wiki/Dirac_delta_function)

This is what I can tell you about the derivation of ‘Delta’ and ‘Dirac’, while nothing else I can say about mathematical reasoning on which the Dirac delta function is based, as this is not my field of expertise, of course.

Hope this helps.
Best,
Maria