Monday, 5 January 2015

homework and exercises - Representing dimensions in Dirac delta function results



The Dirac delta function can be defined as δ(x)=12πeitxdt

From this we see that the dirac function has units of x1.



How do we represent the units in cases like the momentum eigenvectors which, when units are included, is represented as 12π(kg1m1s)eιpx

or 12πeιpx(kg12m12s12)?


Is there a preferred way to write the units(not constrained to SI units, any other system including natural units too) or do we just leave them out, though it would be dimensionally inconsistent without implied units.



Sources I can find for the momentum eigenvector ignore the units of the delta function without even mentioning.


P.S. The problem comes when trying to normalize the momentum operator.


Define ψp(x)=Aeιpx

Over here, A has units of m12.


Normalizing it, ψp1(x)ψp2(x)dx

=|A|2eι(p2p1)xdx
=|A|22πδ(p2p1)
Therefore, ignoring consistency of units, and assuming A is positive, A=12π
Notice that the units do not match




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