Dirac Delta: Normal -> Lognormal?

  • #1
Steve Zissou
53
0
TL;DR Summary
One way to think of the Dirac Delta "function" is the limit of a normal distribution as its standard deviation collapses to an infinitesimal. What if we start with a lognormal?
Hello shipmates,

Instead of imagining a Dirac Delta as the limit of a normal, like this:
$$ \delta\left ( x \right ) = \lim_{a \to 0}\frac{1}{|a|\sqrt{2\pi}}\exp\left [ -\left ( x/a \right )^2 \right ] $$
Could we say the same thing except starting with a lognormal, like this?
$$ \delta_{LN} \left ( x \right ) = \lim_{a \to 0}\frac{1}{|a|x\sqrt{2\pi}}\exp\left [ -\left ( \log{x}/a \right )^2 \right ] $$

Thanks!

Your pal,
Stevsie
 
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  • #2
Then what is physical dimension of x ? It seems x cannot be a physical variable in your formula.
 
Last edited:
  • #3
anuttarasammyak said:
Then what is physical dimension of x ? It seems x cannot be a physical variable in your formula.
x is Specific Gravity. It has no dimensions.
 

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