Does entire and v>0 implies f is constant? [duplicate]












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This question already has an answer here:




  • What might I use to show that an entire function with positive real parts is constant?

    5 answers




Let $f$ : $C$ to $C$ be a function. Assume that $f$ is entire and Im(f(z)) > 0 for all $z$ belongs to $C$. Does that imply $f$ is constant?



I think f will be constant,but can't deduce it
Its easy when the imaginary part(v) is constant but does v>0 also implies that f is constant?



what if v is non-negative that is it can attain $0$ also, will the result remain same?










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marked as duplicate by Martin R, Song, RRL, Lord Shark the Unknown, Leucippus Jan 17 at 6:07


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


















  • $begingroup$
    "$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
    $endgroup$
    – Wojowu
    Jan 15 at 12:06










  • $begingroup$
    Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
    $endgroup$
    – Nilesh Khatri
    Jan 15 at 13:49
















0












$begingroup$



This question already has an answer here:




  • What might I use to show that an entire function with positive real parts is constant?

    5 answers




Let $f$ : $C$ to $C$ be a function. Assume that $f$ is entire and Im(f(z)) > 0 for all $z$ belongs to $C$. Does that imply $f$ is constant?



I think f will be constant,but can't deduce it
Its easy when the imaginary part(v) is constant but does v>0 also implies that f is constant?



what if v is non-negative that is it can attain $0$ also, will the result remain same?










share|cite|improve this question











$endgroup$



marked as duplicate by Martin R, Song, RRL, Lord Shark the Unknown, Leucippus Jan 17 at 6:07


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


















  • $begingroup$
    "$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
    $endgroup$
    – Wojowu
    Jan 15 at 12:06










  • $begingroup$
    Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
    $endgroup$
    – Nilesh Khatri
    Jan 15 at 13:49














0












0








0





$begingroup$



This question already has an answer here:




  • What might I use to show that an entire function with positive real parts is constant?

    5 answers




Let $f$ : $C$ to $C$ be a function. Assume that $f$ is entire and Im(f(z)) > 0 for all $z$ belongs to $C$. Does that imply $f$ is constant?



I think f will be constant,but can't deduce it
Its easy when the imaginary part(v) is constant but does v>0 also implies that f is constant?



what if v is non-negative that is it can attain $0$ also, will the result remain same?










share|cite|improve this question











$endgroup$





This question already has an answer here:




  • What might I use to show that an entire function with positive real parts is constant?

    5 answers




Let $f$ : $C$ to $C$ be a function. Assume that $f$ is entire and Im(f(z)) > 0 for all $z$ belongs to $C$. Does that imply $f$ is constant?



I think f will be constant,but can't deduce it
Its easy when the imaginary part(v) is constant but does v>0 also implies that f is constant?



what if v is non-negative that is it can attain $0$ also, will the result remain same?





This question already has an answer here:




  • What might I use to show that an entire function with positive real parts is constant?

    5 answers








complex-analysis






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 15 at 13:50







Nilesh Khatri

















asked Jan 15 at 12:04









Nilesh KhatriNilesh Khatri

195




195




marked as duplicate by Martin R, Song, RRL, Lord Shark the Unknown, Leucippus Jan 17 at 6:07


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.









marked as duplicate by Martin R, Song, RRL, Lord Shark the Unknown, Leucippus Jan 17 at 6:07


This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.














  • $begingroup$
    "$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
    $endgroup$
    – Wojowu
    Jan 15 at 12:06










  • $begingroup$
    Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
    $endgroup$
    – Nilesh Khatri
    Jan 15 at 13:49


















  • $begingroup$
    "$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
    $endgroup$
    – Wojowu
    Jan 15 at 12:06










  • $begingroup$
    Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
    $endgroup$
    – Nilesh Khatri
    Jan 15 at 13:49
















$begingroup$
"$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
$endgroup$
– Wojowu
Jan 15 at 12:06




$begingroup$
"$f=az+b$ is the only entire function from C to C" ??? This is completely false. What about $f=z^2$ for instance?
$endgroup$
– Wojowu
Jan 15 at 12:06












$begingroup$
Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
$endgroup$
– Nilesh Khatri
Jan 15 at 13:49




$begingroup$
Wojowu you are right,actually i mistaken conformal maps and entire functions,my bad
$endgroup$
– Nilesh Khatri
Jan 15 at 13:49










1 Answer
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active

oldest

votes


















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If $f$ is a non-constant entire function then $f(Bbb C)$ is dense in the plane.





Proof: Suppose that $f(Bbb C)cap D(p,r)=emptyset$. Then $g=dots$ is bounded, hence $g$ is constant, so $f$ is constant.






share|cite|improve this answer









$endgroup$




















    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    0












    $begingroup$



    If $f$ is a non-constant entire function then $f(Bbb C)$ is dense in the plane.





    Proof: Suppose that $f(Bbb C)cap D(p,r)=emptyset$. Then $g=dots$ is bounded, hence $g$ is constant, so $f$ is constant.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$



      If $f$ is a non-constant entire function then $f(Bbb C)$ is dense in the plane.





      Proof: Suppose that $f(Bbb C)cap D(p,r)=emptyset$. Then $g=dots$ is bounded, hence $g$ is constant, so $f$ is constant.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$



        If $f$ is a non-constant entire function then $f(Bbb C)$ is dense in the plane.





        Proof: Suppose that $f(Bbb C)cap D(p,r)=emptyset$. Then $g=dots$ is bounded, hence $g$ is constant, so $f$ is constant.






        share|cite|improve this answer









        $endgroup$





        If $f$ is a non-constant entire function then $f(Bbb C)$ is dense in the plane.





        Proof: Suppose that $f(Bbb C)cap D(p,r)=emptyset$. Then $g=dots$ is bounded, hence $g$ is constant, so $f$ is constant.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 15 at 13:35









        David C. UllrichDavid C. Ullrich

        60.9k43994




        60.9k43994















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