Uniqueness of Finite Additive Measure

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I know that for two measures defined on the Borel set of real line $mu_1$ and $mu_2$, if $mu_1((a,b))=mu_2((a,b))$ for all real numbers a and b, then $mu_1=mu_2$.



Curious on whether similar conditions hold for finite-additive, but not countably additive measures. If $v_1(A)$, $v_2(A)$ are two finitely-additive measures and $v_1(A)$ and $v_2(A)$ are equal for all $A in beta$, in which $beta$ is a collection of Borel sets. What is the 'smallest' $beta$ to ensure that these two measures are equal? You can assume $mu(Omega)=1$ as non-standard probability theory if that's necessary.



If it takes a long story to answer, a book/paper name and author is also welcomed. Many thanks for that.







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    I doubt there exists any interesting such set $beta$.
    – Eric Wofsey
    Jul 18 at 20:35














up vote
3
down vote

favorite
1












I know that for two measures defined on the Borel set of real line $mu_1$ and $mu_2$, if $mu_1((a,b))=mu_2((a,b))$ for all real numbers a and b, then $mu_1=mu_2$.



Curious on whether similar conditions hold for finite-additive, but not countably additive measures. If $v_1(A)$, $v_2(A)$ are two finitely-additive measures and $v_1(A)$ and $v_2(A)$ are equal for all $A in beta$, in which $beta$ is a collection of Borel sets. What is the 'smallest' $beta$ to ensure that these two measures are equal? You can assume $mu(Omega)=1$ as non-standard probability theory if that's necessary.



If it takes a long story to answer, a book/paper name and author is also welcomed. Many thanks for that.







share|cite|improve this question















  • 1




    I doubt there exists any interesting such set $beta$.
    – Eric Wofsey
    Jul 18 at 20:35












up vote
3
down vote

favorite
1









up vote
3
down vote

favorite
1






1





I know that for two measures defined on the Borel set of real line $mu_1$ and $mu_2$, if $mu_1((a,b))=mu_2((a,b))$ for all real numbers a and b, then $mu_1=mu_2$.



Curious on whether similar conditions hold for finite-additive, but not countably additive measures. If $v_1(A)$, $v_2(A)$ are two finitely-additive measures and $v_1(A)$ and $v_2(A)$ are equal for all $A in beta$, in which $beta$ is a collection of Borel sets. What is the 'smallest' $beta$ to ensure that these two measures are equal? You can assume $mu(Omega)=1$ as non-standard probability theory if that's necessary.



If it takes a long story to answer, a book/paper name and author is also welcomed. Many thanks for that.







share|cite|improve this question











I know that for two measures defined on the Borel set of real line $mu_1$ and $mu_2$, if $mu_1((a,b))=mu_2((a,b))$ for all real numbers a and b, then $mu_1=mu_2$.



Curious on whether similar conditions hold for finite-additive, but not countably additive measures. If $v_1(A)$, $v_2(A)$ are two finitely-additive measures and $v_1(A)$ and $v_2(A)$ are equal for all $A in beta$, in which $beta$ is a collection of Borel sets. What is the 'smallest' $beta$ to ensure that these two measures are equal? You can assume $mu(Omega)=1$ as non-standard probability theory if that's necessary.



If it takes a long story to answer, a book/paper name and author is also welcomed. Many thanks for that.









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asked Jul 18 at 20:31









failedstatistician

165




165







  • 1




    I doubt there exists any interesting such set $beta$.
    – Eric Wofsey
    Jul 18 at 20:35












  • 1




    I doubt there exists any interesting such set $beta$.
    – Eric Wofsey
    Jul 18 at 20:35







1




1




I doubt there exists any interesting such set $beta$.
– Eric Wofsey
Jul 18 at 20:35




I doubt there exists any interesting such set $beta$.
– Eric Wofsey
Jul 18 at 20:35










1 Answer
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Finitely additive measures are in isometric correspondence with positive functionals over $L^infty(Omega)$. Since $L^infty(Omega) = C(X)$, where $X$ is the compact Hausdorff topological space given by the Gel'fand spectrum of $L^infty(Omega)$, we have that the finitely additive measures are the positive cone of $C(X)^* = M(X)$, where $M(X)$ are the Borel measures over $X$. The set $beta$ must generate the whole $sigma$-algebra of $X$, for example this happens when $beta$ is a base for the topology of $X$.



Example: When $Omega = mathbbN$, you have that $X = beta mathbbN$, the Stone-Cech compactification of $mathbbN$ and you can take $beta$ (confusing notation) to be $ mathbbN cap V : V in mathcalV subset mathcalP(beta mathbb N) $, where $mathcal V$ is a base for the topology of $beta mathbb N$.






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  • I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
    – failedstatistician
    Jul 22 at 7:09










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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
2
down vote













Finitely additive measures are in isometric correspondence with positive functionals over $L^infty(Omega)$. Since $L^infty(Omega) = C(X)$, where $X$ is the compact Hausdorff topological space given by the Gel'fand spectrum of $L^infty(Omega)$, we have that the finitely additive measures are the positive cone of $C(X)^* = M(X)$, where $M(X)$ are the Borel measures over $X$. The set $beta$ must generate the whole $sigma$-algebra of $X$, for example this happens when $beta$ is a base for the topology of $X$.



Example: When $Omega = mathbbN$, you have that $X = beta mathbbN$, the Stone-Cech compactification of $mathbbN$ and you can take $beta$ (confusing notation) to be $ mathbbN cap V : V in mathcalV subset mathcalP(beta mathbb N) $, where $mathcal V$ is a base for the topology of $beta mathbb N$.






share|cite|improve this answer























  • I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
    – failedstatistician
    Jul 22 at 7:09














up vote
2
down vote













Finitely additive measures are in isometric correspondence with positive functionals over $L^infty(Omega)$. Since $L^infty(Omega) = C(X)$, where $X$ is the compact Hausdorff topological space given by the Gel'fand spectrum of $L^infty(Omega)$, we have that the finitely additive measures are the positive cone of $C(X)^* = M(X)$, where $M(X)$ are the Borel measures over $X$. The set $beta$ must generate the whole $sigma$-algebra of $X$, for example this happens when $beta$ is a base for the topology of $X$.



Example: When $Omega = mathbbN$, you have that $X = beta mathbbN$, the Stone-Cech compactification of $mathbbN$ and you can take $beta$ (confusing notation) to be $ mathbbN cap V : V in mathcalV subset mathcalP(beta mathbb N) $, where $mathcal V$ is a base for the topology of $beta mathbb N$.






share|cite|improve this answer























  • I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
    – failedstatistician
    Jul 22 at 7:09












up vote
2
down vote










up vote
2
down vote









Finitely additive measures are in isometric correspondence with positive functionals over $L^infty(Omega)$. Since $L^infty(Omega) = C(X)$, where $X$ is the compact Hausdorff topological space given by the Gel'fand spectrum of $L^infty(Omega)$, we have that the finitely additive measures are the positive cone of $C(X)^* = M(X)$, where $M(X)$ are the Borel measures over $X$. The set $beta$ must generate the whole $sigma$-algebra of $X$, for example this happens when $beta$ is a base for the topology of $X$.



Example: When $Omega = mathbbN$, you have that $X = beta mathbbN$, the Stone-Cech compactification of $mathbbN$ and you can take $beta$ (confusing notation) to be $ mathbbN cap V : V in mathcalV subset mathcalP(beta mathbb N) $, where $mathcal V$ is a base for the topology of $beta mathbb N$.






share|cite|improve this answer















Finitely additive measures are in isometric correspondence with positive functionals over $L^infty(Omega)$. Since $L^infty(Omega) = C(X)$, where $X$ is the compact Hausdorff topological space given by the Gel'fand spectrum of $L^infty(Omega)$, we have that the finitely additive measures are the positive cone of $C(X)^* = M(X)$, where $M(X)$ are the Borel measures over $X$. The set $beta$ must generate the whole $sigma$-algebra of $X$, for example this happens when $beta$ is a base for the topology of $X$.



Example: When $Omega = mathbbN$, you have that $X = beta mathbbN$, the Stone-Cech compactification of $mathbbN$ and you can take $beta$ (confusing notation) to be $ mathbbN cap V : V in mathcalV subset mathcalP(beta mathbb N) $, where $mathcal V$ is a base for the topology of $beta mathbb N$.







share|cite|improve this answer















share|cite|improve this answer



share|cite|improve this answer








edited Jul 22 at 17:09


























answered Jul 19 at 15:05









Adrián González-Pérez

54138




54138











  • I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
    – failedstatistician
    Jul 22 at 7:09
















  • I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
    – failedstatistician
    Jul 22 at 7:09















I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
– failedstatistician
Jul 22 at 7:09




I have virtually no knowledge on topology beyond metric space and I am totally lost...thanks anyway though.
– failedstatistician
Jul 22 at 7:09












 

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