The measure of the union of 2 sets. The 2019 Stack Overflow Developer Survey Results Are In Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)Using the concept of $G_delta$ sets, show that the union of two measurable sets is measurable.There is a measure $mu^(2)(A_1times A_2)=mu(A_1cap A_2)$Is the measure space $(mathbbR, B(mathbbR),mu)$ complete where $mu$ is the Lesbesgue measure?A question on atoms in measure theory.Outer measure and trace sigma algebraCompletion of a measure space and Null SetsLet $Esubseteq[a,b]$ be measurable. Prove that $overline mA=overline m(Acap E) + overline m(Acap E^c)$ for any $Asubseteq[a,b]$.Completion of a measure space using null setsComplete Measure spacesσ-algebra and measure of the union of 2 sets. Based on measure theory.

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The measure of the union of 2 sets.



The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)Using the concept of $G_delta$ sets, show that the union of two measurable sets is measurable.There is a measure $mu^(2)(A_1times A_2)=mu(A_1cap A_2)$Is the measure space $(mathbbR, B(mathbbR),mu)$ complete where $mu$ is the Lesbesgue measure?A question on atoms in measure theory.Outer measure and trace sigma algebraCompletion of a measure space and Null SetsLet $Esubseteq[a,b]$ be measurable. Prove that $overline mA=overline m(Acap E) + overline m(Acap E^c)$ for any $Asubseteq[a,b]$.Completion of a measure space using null setsComplete Measure spacesσ-algebra and measure of the union of 2 sets. Based on measure theory.










0












$begingroup$


A measure space $(mathbb S,mathcal S,μ)$ is not complete. The system of all its null sets is $mathcal O$.



Let
$$ S′=A∪O:A∈ mathcal S,O∈ mathcal O.$$
The formula of the function $μ′:mathcal S′→[0,∞]$ is
$$μ′(A∪O)=μ(A).$$



Question:



(a) Show: $μ′(A_1∪O_1)=μ′(A_2∪O_2),$ if $A_1∪O_1=A_2∪O_2.$



My solution:



I am given some hints. I need to show that $A=A_1∪O_1=A_2∪O_2$ in two ways, with $A_1,A_2∈ mathcal S$ and $O_1,O_2∈ mathcal O$, then $μ(A_1)=μ(A_2)$. Then according to $μ′(A∪O)=μ(A)$ the final fact will follow.










share|cite|improve this question











$endgroup$
















    0












    $begingroup$


    A measure space $(mathbb S,mathcal S,μ)$ is not complete. The system of all its null sets is $mathcal O$.



    Let
    $$ S′=A∪O:A∈ mathcal S,O∈ mathcal O.$$
    The formula of the function $μ′:mathcal S′→[0,∞]$ is
    $$μ′(A∪O)=μ(A).$$



    Question:



    (a) Show: $μ′(A_1∪O_1)=μ′(A_2∪O_2),$ if $A_1∪O_1=A_2∪O_2.$



    My solution:



    I am given some hints. I need to show that $A=A_1∪O_1=A_2∪O_2$ in two ways, with $A_1,A_2∈ mathcal S$ and $O_1,O_2∈ mathcal O$, then $μ(A_1)=μ(A_2)$. Then according to $μ′(A∪O)=μ(A)$ the final fact will follow.










    share|cite|improve this question











    $endgroup$














      0












      0








      0





      $begingroup$


      A measure space $(mathbb S,mathcal S,μ)$ is not complete. The system of all its null sets is $mathcal O$.



      Let
      $$ S′=A∪O:A∈ mathcal S,O∈ mathcal O.$$
      The formula of the function $μ′:mathcal S′→[0,∞]$ is
      $$μ′(A∪O)=μ(A).$$



      Question:



      (a) Show: $μ′(A_1∪O_1)=μ′(A_2∪O_2),$ if $A_1∪O_1=A_2∪O_2.$



      My solution:



      I am given some hints. I need to show that $A=A_1∪O_1=A_2∪O_2$ in two ways, with $A_1,A_2∈ mathcal S$ and $O_1,O_2∈ mathcal O$, then $μ(A_1)=μ(A_2)$. Then according to $μ′(A∪O)=μ(A)$ the final fact will follow.










      share|cite|improve this question











      $endgroup$




      A measure space $(mathbb S,mathcal S,μ)$ is not complete. The system of all its null sets is $mathcal O$.



      Let
      $$ S′=A∪O:A∈ mathcal S,O∈ mathcal O.$$
      The formula of the function $μ′:mathcal S′→[0,∞]$ is
      $$μ′(A∪O)=μ(A).$$



      Question:



      (a) Show: $μ′(A_1∪O_1)=μ′(A_2∪O_2),$ if $A_1∪O_1=A_2∪O_2.$



      My solution:



      I am given some hints. I need to show that $A=A_1∪O_1=A_2∪O_2$ in two ways, with $A_1,A_2∈ mathcal S$ and $O_1,O_2∈ mathcal O$, then $μ(A_1)=μ(A_2)$. Then according to $μ′(A∪O)=μ(A)$ the final fact will follow.







      measure-theory functions






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      share|cite|improve this question













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      edited Mar 25 at 11:11









      Asaf Karagila

      308k33441775




      308k33441775










      asked Mar 25 at 8:20









      PhilipPhilip

      917




      917




















          1 Answer
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          $begingroup$

          $A_2 setminus A_1 subset O_1 $ so $mu (A_2 setminus A_1)=0$. Similarly, $mu (A_1 setminus A_2)=0$. Now $mu (A_1)leq mu (A_1 setminus A_2)+mu (A_2)=mu(A_2)$ and the reverse inequality is similar.






          share|cite|improve this answer









          $endgroup$













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            $begingroup$

            $A_2 setminus A_1 subset O_1 $ so $mu (A_2 setminus A_1)=0$. Similarly, $mu (A_1 setminus A_2)=0$. Now $mu (A_1)leq mu (A_1 setminus A_2)+mu (A_2)=mu(A_2)$ and the reverse inequality is similar.






            share|cite|improve this answer









            $endgroup$

















              3












              $begingroup$

              $A_2 setminus A_1 subset O_1 $ so $mu (A_2 setminus A_1)=0$. Similarly, $mu (A_1 setminus A_2)=0$. Now $mu (A_1)leq mu (A_1 setminus A_2)+mu (A_2)=mu(A_2)$ and the reverse inequality is similar.






              share|cite|improve this answer









              $endgroup$















                3












                3








                3





                $begingroup$

                $A_2 setminus A_1 subset O_1 $ so $mu (A_2 setminus A_1)=0$. Similarly, $mu (A_1 setminus A_2)=0$. Now $mu (A_1)leq mu (A_1 setminus A_2)+mu (A_2)=mu(A_2)$ and the reverse inequality is similar.






                share|cite|improve this answer









                $endgroup$



                $A_2 setminus A_1 subset O_1 $ so $mu (A_2 setminus A_1)=0$. Similarly, $mu (A_1 setminus A_2)=0$. Now $mu (A_1)leq mu (A_1 setminus A_2)+mu (A_2)=mu(A_2)$ and the reverse inequality is similar.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Mar 25 at 8:29









                Kavi Rama MurthyKavi Rama Murthy

                74.6k53270




                74.6k53270



























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