Integration with Spectral Measure












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Now, suppose I have a compactly supported spectral measure $E$ defined on the Borel subsets of $mathbb{C}$. My question is this, suppose we have a sequence of functions ${f_n}$ non necessarily continuous, converging uniformly to $f$ continuous, is it true that $||int f_{n}dE-int fdE||to 0$? I know the result holds in strong operator topology.










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    1












    $begingroup$


    Now, suppose I have a compactly supported spectral measure $E$ defined on the Borel subsets of $mathbb{C}$. My question is this, suppose we have a sequence of functions ${f_n}$ non necessarily continuous, converging uniformly to $f$ continuous, is it true that $||int f_{n}dE-int fdE||to 0$? I know the result holds in strong operator topology.










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      Now, suppose I have a compactly supported spectral measure $E$ defined on the Borel subsets of $mathbb{C}$. My question is this, suppose we have a sequence of functions ${f_n}$ non necessarily continuous, converging uniformly to $f$ continuous, is it true that $||int f_{n}dE-int fdE||to 0$? I know the result holds in strong operator topology.










      share|cite|improve this question











      $endgroup$




      Now, suppose I have a compactly supported spectral measure $E$ defined on the Borel subsets of $mathbb{C}$. My question is this, suppose we have a sequence of functions ${f_n}$ non necessarily continuous, converging uniformly to $f$ continuous, is it true that $||int f_{n}dE-int fdE||to 0$? I know the result holds in strong operator topology.







      functional-analysis operator-theory spectral-theory






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      edited Dec 9 '18 at 20:17









      Martin Argerami

      127k1182182




      127k1182182










      asked Dec 9 '18 at 19:06









      Kesav KrishnanKesav Krishnan

      201111




      201111






















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          $begingroup$

          Yes. Write $E_h(Delta)=langle E(Delta)h,hrangle$. Then
          $$
          leftlangle
          left|left(int_{mathbb C} (f_n(t)-f(t)),dE(t)right)h,h
          rightrangleright|
          =left|int_{mathbb C}(f_n(t)-f(t)),dE_h right|
          leqint_{mathbb C}|f_n(t)-f(t)|,dE_hleq|f_n-f|_infty.
          $$

          As you can do this for any $h$,
          $$
          left|int_{mathbb C} (f_n(t)-f(t)),dE(t)right|leq|f_n-f|_infty.
          $$






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            $begingroup$

            Yes. Write $E_h(Delta)=langle E(Delta)h,hrangle$. Then
            $$
            leftlangle
            left|left(int_{mathbb C} (f_n(t)-f(t)),dE(t)right)h,h
            rightrangleright|
            =left|int_{mathbb C}(f_n(t)-f(t)),dE_h right|
            leqint_{mathbb C}|f_n(t)-f(t)|,dE_hleq|f_n-f|_infty.
            $$

            As you can do this for any $h$,
            $$
            left|int_{mathbb C} (f_n(t)-f(t)),dE(t)right|leq|f_n-f|_infty.
            $$






            share|cite|improve this answer









            $endgroup$


















              1












              $begingroup$

              Yes. Write $E_h(Delta)=langle E(Delta)h,hrangle$. Then
              $$
              leftlangle
              left|left(int_{mathbb C} (f_n(t)-f(t)),dE(t)right)h,h
              rightrangleright|
              =left|int_{mathbb C}(f_n(t)-f(t)),dE_h right|
              leqint_{mathbb C}|f_n(t)-f(t)|,dE_hleq|f_n-f|_infty.
              $$

              As you can do this for any $h$,
              $$
              left|int_{mathbb C} (f_n(t)-f(t)),dE(t)right|leq|f_n-f|_infty.
              $$






              share|cite|improve this answer









              $endgroup$
















                1












                1








                1





                $begingroup$

                Yes. Write $E_h(Delta)=langle E(Delta)h,hrangle$. Then
                $$
                leftlangle
                left|left(int_{mathbb C} (f_n(t)-f(t)),dE(t)right)h,h
                rightrangleright|
                =left|int_{mathbb C}(f_n(t)-f(t)),dE_h right|
                leqint_{mathbb C}|f_n(t)-f(t)|,dE_hleq|f_n-f|_infty.
                $$

                As you can do this for any $h$,
                $$
                left|int_{mathbb C} (f_n(t)-f(t)),dE(t)right|leq|f_n-f|_infty.
                $$






                share|cite|improve this answer









                $endgroup$



                Yes. Write $E_h(Delta)=langle E(Delta)h,hrangle$. Then
                $$
                leftlangle
                left|left(int_{mathbb C} (f_n(t)-f(t)),dE(t)right)h,h
                rightrangleright|
                =left|int_{mathbb C}(f_n(t)-f(t)),dE_h right|
                leqint_{mathbb C}|f_n(t)-f(t)|,dE_hleq|f_n-f|_infty.
                $$

                As you can do this for any $h$,
                $$
                left|int_{mathbb C} (f_n(t)-f(t)),dE(t)right|leq|f_n-f|_infty.
                $$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Dec 9 '18 at 20:16









                Martin ArgeramiMartin Argerami

                127k1182182




                127k1182182






























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