How big is $|z^w|$ compared to $|z|$?











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I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.










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  • Writing $z$ in polar form might be helpful
    – Aditya Dua
    Nov 16 at 8:47










  • One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
    – Nils Phillip Talgö
    Nov 16 at 9:52

















up vote
0
down vote

favorite












I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.










share|cite|improve this question
























  • Writing $z$ in polar form might be helpful
    – Aditya Dua
    Nov 16 at 8:47










  • One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
    – Nils Phillip Talgö
    Nov 16 at 9:52















up vote
0
down vote

favorite









up vote
0
down vote

favorite











I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.










share|cite|improve this question















I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.







complex-analysis complex-numbers






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edited Nov 16 at 9:41

























asked Nov 14 at 15:18









Nils Phillip Talgö

86




86












  • Writing $z$ in polar form might be helpful
    – Aditya Dua
    Nov 16 at 8:47










  • One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
    – Nils Phillip Talgö
    Nov 16 at 9:52




















  • Writing $z$ in polar form might be helpful
    – Aditya Dua
    Nov 16 at 8:47










  • One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
    – Nils Phillip Talgö
    Nov 16 at 9:52


















Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47




Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47












One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52






One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52












2 Answers
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Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.



By definition, $|z|=r$.



$z^w = z^{a+jb}$



= $z^a z^{jb}$



= $r^a e^{jatheta} r^{jb} e^{-theta b}$



We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.



This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.



Seems hard to simplify beyond this for the most general case.






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  • Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
    – Nils Phillip Talgö
    Nov 18 at 14:58


















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$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$



But notice that the argument is not uniquely defined, you need to choose a branch.



Obviously, for real $w$,



$$|z^w|=|z|^w.$$






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    2 Answers
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    up vote
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    Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.



    By definition, $|z|=r$.



    $z^w = z^{a+jb}$



    = $z^a z^{jb}$



    = $r^a e^{jatheta} r^{jb} e^{-theta b}$



    We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.



    This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.



    Seems hard to simplify beyond this for the most general case.






    share|cite|improve this answer





















    • Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
      – Nils Phillip Talgö
      Nov 18 at 14:58















    up vote
    0
    down vote













    Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.



    By definition, $|z|=r$.



    $z^w = z^{a+jb}$



    = $z^a z^{jb}$



    = $r^a e^{jatheta} r^{jb} e^{-theta b}$



    We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.



    This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.



    Seems hard to simplify beyond this for the most general case.






    share|cite|improve this answer





















    • Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
      – Nils Phillip Talgö
      Nov 18 at 14:58













    up vote
    0
    down vote










    up vote
    0
    down vote









    Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.



    By definition, $|z|=r$.



    $z^w = z^{a+jb}$



    = $z^a z^{jb}$



    = $r^a e^{jatheta} r^{jb} e^{-theta b}$



    We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.



    This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.



    Seems hard to simplify beyond this for the most general case.






    share|cite|improve this answer












    Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.



    By definition, $|z|=r$.



    $z^w = z^{a+jb}$



    = $z^a z^{jb}$



    = $r^a e^{jatheta} r^{jb} e^{-theta b}$



    We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.



    This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.



    Seems hard to simplify beyond this for the most general case.







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Nov 16 at 17:27









    Aditya Dua

    4906




    4906












    • Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
      – Nils Phillip Talgö
      Nov 18 at 14:58


















    • Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
      – Nils Phillip Talgö
      Nov 18 at 14:58
















    Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
    – Nils Phillip Talgö
    Nov 18 at 14:58




    Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
    – Nils Phillip Talgö
    Nov 18 at 14:58










    up vote
    0
    down vote













    $$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$



    But notice that the argument is not uniquely defined, you need to choose a branch.



    Obviously, for real $w$,



    $$|z^w|=|z|^w.$$






    share|cite|improve this answer



























      up vote
      0
      down vote













      $$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$



      But notice that the argument is not uniquely defined, you need to choose a branch.



      Obviously, for real $w$,



      $$|z^w|=|z|^w.$$






      share|cite|improve this answer

























        up vote
        0
        down vote










        up vote
        0
        down vote









        $$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$



        But notice that the argument is not uniquely defined, you need to choose a branch.



        Obviously, for real $w$,



        $$|z^w|=|z|^w.$$






        share|cite|improve this answer














        $$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$



        But notice that the argument is not uniquely defined, you need to choose a branch.



        Obviously, for real $w$,



        $$|z^w|=|z|^w.$$







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Nov 16 at 17:36

























        answered Nov 16 at 17:30









        Yves Daoust

        121k668216




        121k668216






























             

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