Finding the harmonic conjugate given real part












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I have $Im(z)=ln(x^2+y^2)$ and need to find the harmonic conjugate of it.
I'm looking at SO question and its answer Showing that $u(x, , y) = ln(x^2 + y^2)$ is harmonic without computing partial derivatives



The answer there is $2ln z$ but in the book I have it's $2iln z$. So what's missing?










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$endgroup$












  • $begingroup$
    $2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 6:46












  • $begingroup$
    In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 7:17










  • $begingroup$
    actually this is the imaginary part, sorry
    $endgroup$
    – user3132457
    Dec 17 '18 at 15:21
















0












$begingroup$


I have $Im(z)=ln(x^2+y^2)$ and need to find the harmonic conjugate of it.
I'm looking at SO question and its answer Showing that $u(x, , y) = ln(x^2 + y^2)$ is harmonic without computing partial derivatives



The answer there is $2ln z$ but in the book I have it's $2iln z$. So what's missing?










share|cite|improve this question











$endgroup$












  • $begingroup$
    $2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 6:46












  • $begingroup$
    In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 7:17










  • $begingroup$
    actually this is the imaginary part, sorry
    $endgroup$
    – user3132457
    Dec 17 '18 at 15:21














0












0








0


1



$begingroup$


I have $Im(z)=ln(x^2+y^2)$ and need to find the harmonic conjugate of it.
I'm looking at SO question and its answer Showing that $u(x, , y) = ln(x^2 + y^2)$ is harmonic without computing partial derivatives



The answer there is $2ln z$ but in the book I have it's $2iln z$. So what's missing?










share|cite|improve this question











$endgroup$




I have $Im(z)=ln(x^2+y^2)$ and need to find the harmonic conjugate of it.
I'm looking at SO question and its answer Showing that $u(x, , y) = ln(x^2 + y^2)$ is harmonic without computing partial derivatives



The answer there is $2ln z$ but in the book I have it's $2iln z$. So what's missing?







complex-analysis harmonic-analysis






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 17 '18 at 15:21







user3132457

















asked Dec 17 '18 at 6:13









user3132457user3132457

1598




1598












  • $begingroup$
    $2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 6:46












  • $begingroup$
    In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 7:17










  • $begingroup$
    actually this is the imaginary part, sorry
    $endgroup$
    – user3132457
    Dec 17 '18 at 15:21


















  • $begingroup$
    $2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 6:46












  • $begingroup$
    In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
    $endgroup$
    – Kavi Rama Murthy
    Dec 17 '18 at 7:17










  • $begingroup$
    actually this is the imaginary part, sorry
    $endgroup$
    – user3132457
    Dec 17 '18 at 15:21
















$begingroup$
$2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
$endgroup$
– Kavi Rama Murthy
Dec 17 '18 at 6:46






$begingroup$
$2 Log , z$ is an analytic function in $mathbb C setminus (-infty, 0]$ with real part $ln (x^{2}+y^{2})$ where Log denotes the principal branch of logarithm. I have not seen people wiring ln for principle logarithm.
$endgroup$
– Kavi Rama Murthy
Dec 17 '18 at 6:46














$begingroup$
In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
$endgroup$
– Kavi Rama Murthy
Dec 17 '18 at 7:17




$begingroup$
In what region are you trying to find the harmonic conjugate? Your function does not have a harmonic conjugate in $mathbb Csetminus {0}$.
$endgroup$
– Kavi Rama Murthy
Dec 17 '18 at 7:17












$begingroup$
actually this is the imaginary part, sorry
$endgroup$
– user3132457
Dec 17 '18 at 15:21




$begingroup$
actually this is the imaginary part, sorry
$endgroup$
– user3132457
Dec 17 '18 at 15:21










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