Sunday, December 7, 2014

Another Take On Discrete

From the post "Quantized x, Discretely",

\(\int { \cfrac { 1 }{ \psi  }  } d\, \psi +\int { \int { \cfrac { 1 }{ \psi ^{ 2 } }  }  } \left( d\, \psi  \right) ^{ 2 }=n^{ 2 }ln(x)+Ax+C\)

where both \(A\) and \(C\) are constants for all \(x\).  Simplifying further we have,

\(n^{ 2 }ln(x)+Ax+C=0\) --- (*)

when \(x=1\),

\(C=-A\)

So the constrain on \(x\) is,

\(x=e^{ -\cfrac { Ax+C }{ n^{ 2 } }  }\)

\(x=e^{ -\cfrac {A( x-1) }{ n^{ 2 } }  }\)

This is wrong because \(x=1\) will then always be a solution irrespective of \(n\). And we have a unit circle onto which we can pack infinite number waves, as \(n\rightarrow\infty\).  \(x=1\) is not part of the final solution developed previously.

If we consider,

\(x\rightarrow0\)

\(n\rightarrow0\)

As,

\(\lim\limits_{x\rightarrow0 \, n\rightarrow0}n^{ 2 }ln(x)=0^{ 2 }.\infty=0\)

(*) becomes,

\(0^{ 2 }.\infty+A.0+C=0\)

\(C=0\)

And the constrain on \(x\) is,

\(x=e^{ -\cfrac { Ax}{ n^{ 2 } }  }\)

And the constrain on \(f\) is,

\(f=\cfrac{nc}{2\pi}e^{ \cfrac { A }{ 2\pi\,n } \cfrac { c }{ f }  }\)

by substituting \(2\pi x=n\lambda\) and \(\lambda=\cfrac{c}{f}\)

A plot of y=n/(2*Pi)*(e^{1/(2*Pi*n*x)}) and y=n/(2*Pi)*(e^{8/(2*Pi*n*x)}) together with the line y=x, are shown below.


The value of \(f\) for \(n=1\) is folded up for larger values of \(A=8\).  A plot for high value of \(A=30\), y=n/(2*Pi)*(e^{30/(2*Pi*n*x)}) with y=x is shown below.


More intersections between \(y=x\) and \(y=\cfrac{nc}{2\pi}e^{ \cfrac { A }{ 2\pi\,n } \cfrac { c }{ x }  }\) are folded up producing pairs of closely spaced solutions of frequencies, \(f\), when \(A\) is large.

Note: In the plot for \(f\), \(c\) was set to \(1\).  The effect is the same as scaling \(f\) by \(\cfrac{1}{c}\).