Fourier Transform of Entropic Utility Function











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I'm trying find the Fourier transform $F(u)$ for the utility function for the entropic risk measure, which is given below. However my knowledge on Fourier analysis is fairly poor.



$f(x)=dfrac{e^{gamma x}-1}{gamma} $



I'm running into problems because when I try to do the integration I end up evaluating $dfrac{e^{x(gamma +iu)}}{gamma (gamma +iu)}-dfrac{e^{iux}}{iugamma}$ at infinity. Could anyone shed some light on what I'm messing up?










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  • How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
    – Mattos
    Nov 21 at 13:08












  • $e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
    – Andy Walls
    Nov 23 at 2:34

















up vote
0
down vote

favorite












I'm trying find the Fourier transform $F(u)$ for the utility function for the entropic risk measure, which is given below. However my knowledge on Fourier analysis is fairly poor.



$f(x)=dfrac{e^{gamma x}-1}{gamma} $



I'm running into problems because when I try to do the integration I end up evaluating $dfrac{e^{x(gamma +iu)}}{gamma (gamma +iu)}-dfrac{e^{iux}}{iugamma}$ at infinity. Could anyone shed some light on what I'm messing up?










share|cite|improve this question






















  • How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
    – Mattos
    Nov 21 at 13:08












  • $e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
    – Andy Walls
    Nov 23 at 2:34















up vote
0
down vote

favorite









up vote
0
down vote

favorite











I'm trying find the Fourier transform $F(u)$ for the utility function for the entropic risk measure, which is given below. However my knowledge on Fourier analysis is fairly poor.



$f(x)=dfrac{e^{gamma x}-1}{gamma} $



I'm running into problems because when I try to do the integration I end up evaluating $dfrac{e^{x(gamma +iu)}}{gamma (gamma +iu)}-dfrac{e^{iux}}{iugamma}$ at infinity. Could anyone shed some light on what I'm messing up?










share|cite|improve this question













I'm trying find the Fourier transform $F(u)$ for the utility function for the entropic risk measure, which is given below. However my knowledge on Fourier analysis is fairly poor.



$f(x)=dfrac{e^{gamma x}-1}{gamma} $



I'm running into problems because when I try to do the integration I end up evaluating $dfrac{e^{x(gamma +iu)}}{gamma (gamma +iu)}-dfrac{e^{iux}}{iugamma}$ at infinity. Could anyone shed some light on what I'm messing up?







fourier-transform






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asked Nov 21 at 12:55









shrut9

204




204












  • How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
    – Mattos
    Nov 21 at 13:08












  • $e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
    – Andy Walls
    Nov 23 at 2:34




















  • How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
    – Mattos
    Nov 21 at 13:08












  • $e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
    – Andy Walls
    Nov 23 at 2:34


















How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
– Mattos
Nov 21 at 13:08






How do you compute the Fourier transform of $f$ when $f notin L^{1}(mathbb{R})$? Note that if $gamma > 0$ then $f$ blows up at $+infty$ and if $gamma < 0$ then $f$ blows up at $-infty$. Could you show us your working?
– Mattos
Nov 21 at 13:08














$e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
– Andy Walls
Nov 23 at 2:34






$e^{gamma x}$ does not have a Fourier Transform even in a distributional sense. $e^{-|gamma x|}$ does have a Fourier Transform.
– Andy Walls
Nov 23 at 2:34

















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