Relation between $L^p$ spaces.












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We say $fin L_{p}(U)$ if $int_{U}|f|^{p}<infty$.



Can we say $uin L_{4} iff u^{2} in L_{2}$, and $u in L_{2} iff u^{1/2} in L_{4}$










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$endgroup$

















    0












    $begingroup$


    We say $fin L_{p}(U)$ if $int_{U}|f|^{p}<infty$.



    Can we say $uin L_{4} iff u^{2} in L_{2}$, and $u in L_{2} iff u^{1/2} in L_{4}$










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      We say $fin L_{p}(U)$ if $int_{U}|f|^{p}<infty$.



      Can we say $uin L_{4} iff u^{2} in L_{2}$, and $u in L_{2} iff u^{1/2} in L_{4}$










      share|cite|improve this question











      $endgroup$




      We say $fin L_{p}(U)$ if $int_{U}|f|^{p}<infty$.



      Can we say $uin L_{4} iff u^{2} in L_{2}$, and $u in L_{2} iff u^{1/2} in L_{4}$







      functional-analysis lebesgue-measure lp-spaces






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      share|cite|improve this question













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      share|cite|improve this question








      edited Dec 28 '18 at 19:56







      Monty

















      asked Dec 24 '18 at 14:44









      MontyMonty

      34613




      34613






















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          $begingroup$

          Yes, that is correct, because of the identity $lvert x^nrvert=lvert xrvert^n$, which holds for all $xinBbb C$ and $ninBbb Z$. For $nnotin Bbb Z$ there is the definition issue of what $x^n$ is when $xnotin[0,infty)$, in which case $f^n$ is arguably not defined.






          share|cite|improve this answer









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          • $begingroup$
            Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
            $endgroup$
            – Monty
            Dec 24 '18 at 14:58











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          $begingroup$

          Yes, that is correct, because of the identity $lvert x^nrvert=lvert xrvert^n$, which holds for all $xinBbb C$ and $ninBbb Z$. For $nnotin Bbb Z$ there is the definition issue of what $x^n$ is when $xnotin[0,infty)$, in which case $f^n$ is arguably not defined.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
            $endgroup$
            – Monty
            Dec 24 '18 at 14:58
















          2












          $begingroup$

          Yes, that is correct, because of the identity $lvert x^nrvert=lvert xrvert^n$, which holds for all $xinBbb C$ and $ninBbb Z$. For $nnotin Bbb Z$ there is the definition issue of what $x^n$ is when $xnotin[0,infty)$, in which case $f^n$ is arguably not defined.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
            $endgroup$
            – Monty
            Dec 24 '18 at 14:58














          2












          2








          2





          $begingroup$

          Yes, that is correct, because of the identity $lvert x^nrvert=lvert xrvert^n$, which holds for all $xinBbb C$ and $ninBbb Z$. For $nnotin Bbb Z$ there is the definition issue of what $x^n$ is when $xnotin[0,infty)$, in which case $f^n$ is arguably not defined.






          share|cite|improve this answer









          $endgroup$



          Yes, that is correct, because of the identity $lvert x^nrvert=lvert xrvert^n$, which holds for all $xinBbb C$ and $ninBbb Z$. For $nnotin Bbb Z$ there is the definition issue of what $x^n$ is when $xnotin[0,infty)$, in which case $f^n$ is arguably not defined.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 24 '18 at 14:46









          Saucy O'PathSaucy O'Path

          6,0491627




          6,0491627












          • $begingroup$
            Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
            $endgroup$
            – Monty
            Dec 24 '18 at 14:58


















          • $begingroup$
            Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
            $endgroup$
            – Monty
            Dec 24 '18 at 14:58
















          $begingroup$
          Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
          $endgroup$
          – Monty
          Dec 24 '18 at 14:58




          $begingroup$
          Yes, so can use this to work with functions $u^{2}$ in $L_{2}$ ? i.e see my edit.
          $endgroup$
          – Monty
          Dec 24 '18 at 14:58


















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