Composition of convex and $L^1$ function is not $L^1$ function.











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Give an example of functions $fin L^1$ and $varphi$ is convex such that $varphicirc fnotin L^1$ but $$varphi left(int limits_{X}f dmuright)leq intlimits_{X} varphi circ f dmu.$$ I suspect that $f$ should be some function which blows up and $varphi$ some power of its. But I am not able to make it rigorous. Can anyone help with this example, please.










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    Give an example of functions $fin L^1$ and $varphi$ is convex such that $varphicirc fnotin L^1$ but $$varphi left(int limits_{X}f dmuright)leq intlimits_{X} varphi circ f dmu.$$ I suspect that $f$ should be some function which blows up and $varphi$ some power of its. But I am not able to make it rigorous. Can anyone help with this example, please.










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      Give an example of functions $fin L^1$ and $varphi$ is convex such that $varphicirc fnotin L^1$ but $$varphi left(int limits_{X}f dmuright)leq intlimits_{X} varphi circ f dmu.$$ I suspect that $f$ should be some function which blows up and $varphi$ some power of its. But I am not able to make it rigorous. Can anyone help with this example, please.










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      Give an example of functions $fin L^1$ and $varphi$ is convex such that $varphicirc fnotin L^1$ but $$varphi left(int limits_{X}f dmuright)leq intlimits_{X} varphi circ f dmu.$$ I suspect that $f$ should be some function which blows up and $varphi$ some power of its. But I am not able to make it rigorous. Can anyone help with this example, please.







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      asked Nov 15 at 19:03









      ZFR

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          How about $X = [0,1]$, $mu$ is Lebesgue measure, $f(x) = dfrac 1{sqrt x}$, and $phi(x) = x^2$.






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            How about $X = [0,1]$, $mu$ is Lebesgue measure, $f(x) = dfrac 1{sqrt x}$, and $phi(x) = x^2$.






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              How about $X = [0,1]$, $mu$ is Lebesgue measure, $f(x) = dfrac 1{sqrt x}$, and $phi(x) = x^2$.






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                How about $X = [0,1]$, $mu$ is Lebesgue measure, $f(x) = dfrac 1{sqrt x}$, and $phi(x) = x^2$.






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                How about $X = [0,1]$, $mu$ is Lebesgue measure, $f(x) = dfrac 1{sqrt x}$, and $phi(x) = x^2$.







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                answered Nov 15 at 19:07









                Umberto P.

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