Difference between revisions of "Integral of a simple function (measure theory)/Definition"

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(Created page with "<noinclude> {{Stub page|Quickly written. Needs to go something like "using every simple function has a standard representation" and then showing that the integral is the same...")
 
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{{Stub page|Quickly written. Needs to go something like "using every simple function has a standard representation" and then showing that the integral is the same for each standard representation is what needs to be done}}
 
{{Stub page|Quickly written. Needs to go something like "using every simple function has a standard representation" and then showing that the integral is the same for each standard representation is what needs to be done}}
 
==Definition==
 
==Definition==
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</noinclude>For a [[simple function (measure theory)|simple function]] in its [[standard representation (measure theory)|standard representation]], say {{M|1=f:=\sum^n_{i=0}x_i\mathbf{1}_{A_i} }} then the {{M|\mu}}-integral, {{M|I_\mu:\mathcal{E}^+\rightarrow\mathbb{R} }} is{{rMIAMRLS}}:
For a [[simple function (measure theory)|simple function]] in its [[standard representation (measure theory)|standard representation]], say {{M|1=f:=\sum^n_{i=0}x_i\mathbf{1}_{A_i} }} then the {{M|\mu}}-integral, {{M|I_\mu:\mathcal{E}^+\rightarrow\mathbb{R} }} is{{rMIAMRLS}}:
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* {{MM|1=I_\mu(f):=\sum^n_{i=1}x_i\mu(A_i)\in[0,\infty]}}
 
* {{MM|1=I_\mu(f):=\sum^n_{i=1}x_i\mu(A_i)\in[0,\infty]}}
 
Note that this is independent of the particular ''standard representation'' of {{M|f}}.
 
Note that this is independent of the particular ''standard representation'' of {{M|f}}.

Latest revision as of 17:05, 17 March 2016


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Quickly written. Needs to go something like "using every simple function has a standard representation" and then showing that the integral is the same for each standard representation is what needs to be done

Definition

For a simple function in its standard representation, say [ilmath]f:=\sum^n_{i=0}x_i\mathbf{1}_{A_i}[/ilmath] then the [ilmath]\mu[/ilmath]-integral, [ilmath]I_\mu:\mathcal{E}^+\rightarrow\mathbb{R} [/ilmath] is[1]:

  • [math]I_\mu(f):=\sum^n_{i=1}x_i\mu(A_i)\in[0,\infty][/math]

Note that this is independent of the particular standard representation of [ilmath]f[/ilmath].

References

  1. Measures, Integrals and Martingales - René L. Schilling