Problem 3. Page 240. Barry Simon. (Associated Lebesgue-Stieltjes measure )












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In $[0,1]$ let $M$ consists of all finite unions of sets of the form $[c,d)$ where $c,d$ are rational, or $[c,1]$ where $c$ is rational.
($M$ is a algebra).



Given a monotone function $bar{alpha}$, if $([c_j,d_j))_{j=1}^{l}$ is a disjoint finite family of half-open intervals.
Let $alpha(bigcup_{j=1}^{l} [c_j,d_j) )=sum_{j=1}^{l} (bar{alpha}(d_j)-bar{alpha}(c_j))$ finitely additive.



In $M$, let $bar{alpha}(x)=0$ if $x<1/2$ and $bar{alpha}(x)=1$ if $xgeq 1/2.$



Prove that the associated Lebesgue-Stieltjes measure $mu$ has $mu(A)=0$ if $1/2notin A$ and $mu(A)=1$ if $1/2in A$.
For any Baire set $A.$



I have this:
$mu(A)=int_{X} mathcal{X}_{A}d(bar{alpha})=lim_n sum_{j=1}^{n-1} mathcal{X}_{A}(x_j)(bar{alpha}(x_{j+1})-bar{alpha}(x_{j}))$



Why this sum is $0$ when $1/2not in A?$










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    0














    In $[0,1]$ let $M$ consists of all finite unions of sets of the form $[c,d)$ where $c,d$ are rational, or $[c,1]$ where $c$ is rational.
    ($M$ is a algebra).



    Given a monotone function $bar{alpha}$, if $([c_j,d_j))_{j=1}^{l}$ is a disjoint finite family of half-open intervals.
    Let $alpha(bigcup_{j=1}^{l} [c_j,d_j) )=sum_{j=1}^{l} (bar{alpha}(d_j)-bar{alpha}(c_j))$ finitely additive.



    In $M$, let $bar{alpha}(x)=0$ if $x<1/2$ and $bar{alpha}(x)=1$ if $xgeq 1/2.$



    Prove that the associated Lebesgue-Stieltjes measure $mu$ has $mu(A)=0$ if $1/2notin A$ and $mu(A)=1$ if $1/2in A$.
    For any Baire set $A.$



    I have this:
    $mu(A)=int_{X} mathcal{X}_{A}d(bar{alpha})=lim_n sum_{j=1}^{n-1} mathcal{X}_{A}(x_j)(bar{alpha}(x_{j+1})-bar{alpha}(x_{j}))$



    Why this sum is $0$ when $1/2not in A?$










    share|cite|improve this question

























      0












      0








      0







      In $[0,1]$ let $M$ consists of all finite unions of sets of the form $[c,d)$ where $c,d$ are rational, or $[c,1]$ where $c$ is rational.
      ($M$ is a algebra).



      Given a monotone function $bar{alpha}$, if $([c_j,d_j))_{j=1}^{l}$ is a disjoint finite family of half-open intervals.
      Let $alpha(bigcup_{j=1}^{l} [c_j,d_j) )=sum_{j=1}^{l} (bar{alpha}(d_j)-bar{alpha}(c_j))$ finitely additive.



      In $M$, let $bar{alpha}(x)=0$ if $x<1/2$ and $bar{alpha}(x)=1$ if $xgeq 1/2.$



      Prove that the associated Lebesgue-Stieltjes measure $mu$ has $mu(A)=0$ if $1/2notin A$ and $mu(A)=1$ if $1/2in A$.
      For any Baire set $A.$



      I have this:
      $mu(A)=int_{X} mathcal{X}_{A}d(bar{alpha})=lim_n sum_{j=1}^{n-1} mathcal{X}_{A}(x_j)(bar{alpha}(x_{j+1})-bar{alpha}(x_{j}))$



      Why this sum is $0$ when $1/2not in A?$










      share|cite|improve this question













      In $[0,1]$ let $M$ consists of all finite unions of sets of the form $[c,d)$ where $c,d$ are rational, or $[c,1]$ where $c$ is rational.
      ($M$ is a algebra).



      Given a monotone function $bar{alpha}$, if $([c_j,d_j))_{j=1}^{l}$ is a disjoint finite family of half-open intervals.
      Let $alpha(bigcup_{j=1}^{l} [c_j,d_j) )=sum_{j=1}^{l} (bar{alpha}(d_j)-bar{alpha}(c_j))$ finitely additive.



      In $M$, let $bar{alpha}(x)=0$ if $x<1/2$ and $bar{alpha}(x)=1$ if $xgeq 1/2.$



      Prove that the associated Lebesgue-Stieltjes measure $mu$ has $mu(A)=0$ if $1/2notin A$ and $mu(A)=1$ if $1/2in A$.
      For any Baire set $A.$



      I have this:
      $mu(A)=int_{X} mathcal{X}_{A}d(bar{alpha})=lim_n sum_{j=1}^{n-1} mathcal{X}_{A}(x_j)(bar{alpha}(x_{j+1})-bar{alpha}(x_{j}))$



      Why this sum is $0$ when $1/2not in A?$







      real-analysis measure-theory lebesgue-measure stieltjes-integral






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      share|cite|improve this question










      asked Nov 25 at 20:57









      eraldcoil

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