Understanding a proof. Why is it necessary that $alpha<1$?












1












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I'm reading the following proof from Lang's book of complex analysis. But I don't know why is it necessary that $alpha<1$?. I don't know where "$alpha<1$" is used . I don't understand either why $|g_{epsilon}(s)|to 0$ as $|s| to infty$. Can you help me, please?. I have been stuck for many hours.



Thank you for any help.



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  • 1




    $begingroup$
    The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:32












  • $begingroup$
    I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
    $endgroup$
    – KSM1743
    Dec 6 '18 at 22:39






  • 3




    $begingroup$
    The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:43
















1












$begingroup$


I'm reading the following proof from Lang's book of complex analysis. But I don't know why is it necessary that $alpha<1$?. I don't know where "$alpha<1$" is used . I don't understand either why $|g_{epsilon}(s)|to 0$ as $|s| to infty$. Can you help me, please?. I have been stuck for many hours.



Thank you for any help.



enter image description here










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:32












  • $begingroup$
    I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
    $endgroup$
    – KSM1743
    Dec 6 '18 at 22:39






  • 3




    $begingroup$
    The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:43














1












1








1


2



$begingroup$


I'm reading the following proof from Lang's book of complex analysis. But I don't know why is it necessary that $alpha<1$?. I don't know where "$alpha<1$" is used . I don't understand either why $|g_{epsilon}(s)|to 0$ as $|s| to infty$. Can you help me, please?. I have been stuck for many hours.



Thank you for any help.



enter image description here










share|cite|improve this question











$endgroup$




I'm reading the following proof from Lang's book of complex analysis. But I don't know why is it necessary that $alpha<1$?. I don't know where "$alpha<1$" is used . I don't understand either why $|g_{epsilon}(s)|to 0$ as $|s| to infty$. Can you help me, please?. I have been stuck for many hours.



Thank you for any help.



enter image description here







complex-analysis complex-numbers






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 6 '18 at 22:34







KSM1743

















asked Dec 6 '18 at 22:25









KSM1743KSM1743

164




164








  • 1




    $begingroup$
    The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:32












  • $begingroup$
    I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
    $endgroup$
    – KSM1743
    Dec 6 '18 at 22:39






  • 3




    $begingroup$
    The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:43














  • 1




    $begingroup$
    The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:32












  • $begingroup$
    I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
    $endgroup$
    – KSM1743
    Dec 6 '18 at 22:39






  • 3




    $begingroup$
    The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
    $endgroup$
    – AlexanderJ93
    Dec 6 '18 at 22:43








1




1




$begingroup$
The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
$endgroup$
– AlexanderJ93
Dec 6 '18 at 22:32






$begingroup$
The proof starts with "Let $alpha < beta < 1$". What happens if $beta < alpha$?
$endgroup$
– AlexanderJ93
Dec 6 '18 at 22:32














$begingroup$
I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
$endgroup$
– KSM1743
Dec 6 '18 at 22:39




$begingroup$
I think that $g_{epsilon}$ might fail to be bounded on the strip. But, if $alpha geq 1$, we could take $beta in (alpha, alpha+1)$ to show the theorem?
$endgroup$
– KSM1743
Dec 6 '18 at 22:39




3




3




$begingroup$
The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
$endgroup$
– AlexanderJ93
Dec 6 '18 at 22:43




$begingroup$
The proof relies on $0<beta<1$, since that is a requirement for $cos(betasigma) > 0$ for all $sigmain[-pi/2,pi/2]$.
$endgroup$
– AlexanderJ93
Dec 6 '18 at 22:43










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