In the complex field, is this function Harmonic?

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SUMMARY

The function Log|z| is confirmed to be harmonic in the punctured complex plane due to its relationship with the analytic function Log z. Log z is analytic everywhere except along the nonpositive real axis, which implies that Log|z| inherits harmonic properties in regions where z is non-zero. The discussion highlights the theorem that states if a function f = u + iv is analytic, then the real part u is harmonic, reinforcing the conclusion that Log|z| is indeed harmonic.

PREREQUISITES
  • Understanding of complex analysis concepts, specifically harmonic functions.
  • Familiarity with analytic functions and their properties.
  • Knowledge of the logarithmic function in the context of complex variables.
  • Awareness of the nonpositive real axis and its implications in complex analysis.
NEXT STEPS
  • Study the properties of harmonic functions in complex analysis.
  • Explore the relationship between analytic functions and their real and imaginary components.
  • Investigate the implications of the nonpositive real axis on complex functions.
  • Review theorems related to harmonic functions and their derivations from analytic functions.
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Students of complex analysis, mathematicians exploring harmonic functions, and educators teaching the properties of analytic functions in the context of complex variables.

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Homework Statement


Without directly verifying via the laplace equations, explain why Log|z| is harmonic in the punctured complex plane.

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The Attempt at a Solution


I thought it was because Log z is analytic on the complex plane except for the nonpositive real axis, so Log |z| would be analytic and hence harmonic since any |z| turns z into a positive real (for z=/= 0), hence Log |z| is like Log z for positive reals. But, if it's that, why would they ask to show its harmonic and not analytic.
 
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Do you have the theorem that if f=u+iv is analytic then u is harmonic?
 

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