How to Obtain g(x) from f(z) for a Given Equation and Distribution?

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SUMMARY

The discussion focuses on the relationship between functions f(z) and g(x) defined by the equation f(x+iε) - f(x-iε) = g(x), where ε approaches 0. It is established that if f(z) is known for all complex z, g(x) can be derived from this difference. However, the reverse is not possible; knowing g(x) does not allow for the unique determination of f(z) due to the potential addition of any continuous function to f(z) without altering g(x). The assumption is made that f(z) is discontinuous perpendicular to the real axis, which complicates the analysis.

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given any function (or maybe distribution) f(x) and g(x) so

[tex]f(x+i\epsilon ) - f(x-i\epsilon ) = g(x)[/tex]

if we know f(x) could we obtain g(x) from the difference above ??

if we knew g(x) could we solve the equation to get f(x) ??

here [tex]\epsilon \rightarrow 0[/tex]
 
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For the first question, if you know f(z) for all complex z, you can get g(x). For the second question the answer is no, since you can add any continuous function to f(z) and still get the same g(x).

I presume that f(z) is discontinuous perpendicular to the real axis, otherwise the question is trivial.
 

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