Invariant subspace for Volterra operator The Next CEO of Stack OverflowInvariant spaces for a shift semigroupContinuity domain for momentum operatorBoundedness of Volterra operator with Sobolev normInvariant Subspace Problem: Non-Seperable Hilbert SpaceTent map invariant densityDirect numerical solutions for first kind Volterra integral equationsProof that $L^p$ is complete in Folland's Real AnalysisVolterra Operator PropertyMixed formulation with Volterra integrals?Subspace of $alpha$ Holder continuous functions is Closed

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Invariant subspace for Volterra operator



The Next CEO of Stack OverflowInvariant spaces for a shift semigroupContinuity domain for momentum operatorBoundedness of Volterra operator with Sobolev normInvariant Subspace Problem: Non-Seperable Hilbert SpaceTent map invariant densityDirect numerical solutions for first kind Volterra integral equationsProof that $L^p$ is complete in Folland's Real AnalysisVolterra Operator PropertyMixed formulation with Volterra integrals?Subspace of $alpha$ Holder continuous functions is Closed










1












$begingroup$


So, am I stupid or isn't this kind of trivial?



I'm having this problem:



Let $T$ be the Volterra operator on $L^2([0,1])$ defined by
beginequation
Tf(s) = int^s_0 , f(t) , textdt.
endequation

For $0 leq alpha leq 1$ set
beginequation
M_alpha = f in L^2([0,1]) : f(t) = 0, 0 leq t leq alpha.
endequation



Prove that each $M_alpha$ is an invariant subspace for $T$.



My solution is this:



$M_alpha$ is an invariant subspace for $T$ if $f(t) in M_alpha Rightarrow Tf(s) in M_alpha$. So if $f(t) in M_alpha$, then



beginequation*
beginaligned
Tf(s) &= int^s_0 , f(t) , textdt\
&= begincasesdisplaystyleint^s_0 , 0 , textdt &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) , textdt &quad textif alpha < t leq 1\endcases\
&= begincases0 &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) textdt &quad textif alpha < t leq 1\endcases\
&in M_alpha
endaligned
endequation*



Am I wrong or is it this simple?










share|cite|improve this question









$endgroup$
















    1












    $begingroup$


    So, am I stupid or isn't this kind of trivial?



    I'm having this problem:



    Let $T$ be the Volterra operator on $L^2([0,1])$ defined by
    beginequation
    Tf(s) = int^s_0 , f(t) , textdt.
    endequation

    For $0 leq alpha leq 1$ set
    beginequation
    M_alpha = f in L^2([0,1]) : f(t) = 0, 0 leq t leq alpha.
    endequation



    Prove that each $M_alpha$ is an invariant subspace for $T$.



    My solution is this:



    $M_alpha$ is an invariant subspace for $T$ if $f(t) in M_alpha Rightarrow Tf(s) in M_alpha$. So if $f(t) in M_alpha$, then



    beginequation*
    beginaligned
    Tf(s) &= int^s_0 , f(t) , textdt\
    &= begincasesdisplaystyleint^s_0 , 0 , textdt &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) , textdt &quad textif alpha < t leq 1\endcases\
    &= begincases0 &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) textdt &quad textif alpha < t leq 1\endcases\
    &in M_alpha
    endaligned
    endequation*



    Am I wrong or is it this simple?










    share|cite|improve this question









    $endgroup$














      1












      1








      1





      $begingroup$


      So, am I stupid or isn't this kind of trivial?



      I'm having this problem:



      Let $T$ be the Volterra operator on $L^2([0,1])$ defined by
      beginequation
      Tf(s) = int^s_0 , f(t) , textdt.
      endequation

      For $0 leq alpha leq 1$ set
      beginequation
      M_alpha = f in L^2([0,1]) : f(t) = 0, 0 leq t leq alpha.
      endequation



      Prove that each $M_alpha$ is an invariant subspace for $T$.



      My solution is this:



      $M_alpha$ is an invariant subspace for $T$ if $f(t) in M_alpha Rightarrow Tf(s) in M_alpha$. So if $f(t) in M_alpha$, then



      beginequation*
      beginaligned
      Tf(s) &= int^s_0 , f(t) , textdt\
      &= begincasesdisplaystyleint^s_0 , 0 , textdt &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) , textdt &quad textif alpha < t leq 1\endcases\
      &= begincases0 &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) textdt &quad textif alpha < t leq 1\endcases\
      &in M_alpha
      endaligned
      endequation*



      Am I wrong or is it this simple?










      share|cite|improve this question









      $endgroup$




      So, am I stupid or isn't this kind of trivial?



      I'm having this problem:



      Let $T$ be the Volterra operator on $L^2([0,1])$ defined by
      beginequation
      Tf(s) = int^s_0 , f(t) , textdt.
      endequation

      For $0 leq alpha leq 1$ set
      beginequation
      M_alpha = f in L^2([0,1]) : f(t) = 0, 0 leq t leq alpha.
      endequation



      Prove that each $M_alpha$ is an invariant subspace for $T$.



      My solution is this:



      $M_alpha$ is an invariant subspace for $T$ if $f(t) in M_alpha Rightarrow Tf(s) in M_alpha$. So if $f(t) in M_alpha$, then



      beginequation*
      beginaligned
      Tf(s) &= int^s_0 , f(t) , textdt\
      &= begincasesdisplaystyleint^s_0 , 0 , textdt &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) , textdt &quad textif alpha < t leq 1\endcases\
      &= begincases0 &quad textif 0 leq t leq alpha\displaystyleint^s_0 , f(t) textdt &quad textif alpha < t leq 1\endcases\
      &in M_alpha
      endaligned
      endequation*



      Am I wrong or is it this simple?







      functional-analysis hilbert-spaces






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Mar 19 at 21:59









      Emil TonklingaEmil Tonklinga

      62




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