Conditional expectation in L2 #
This file contains one step of the construction of the conditional expectation, which is completed
in MeasureTheory.Function.ConditionalExpectation.Basic. See that file for a description of the
full process.
We build the conditional expectation of an L² function, as an element of L². This is the
orthogonal projection on the subspace of almost everywhere m-measurable functions.
Main definitions #
condexpL2: Conditional expectation of a function in L2 with respect to a sigma-algebra: it is the orthogonal projection on the subspacelpMeas.
Implementation notes #
Most of the results in this file are valid for a complete real normed space F.
However, some lemmas also use 𝕜 : RCLike:
condexpL2is defined only for anInnerProductSpacefor now, and we use𝕜for its field.- results about scalar multiplication are stated not only for
ℝbut also for𝕜if we happen to haveNormedSpace 𝕜 F.
Conditional expectation of a function in L2 with respect to a sigma-algebra
Equations
- MeasureTheory.condexpL2 E 𝕜 hm = orthogonalProjection (MeasureTheory.lpMeas E 𝕜 m 2 μ)
Instances For
condexpL2 commutes with taking inner products with constants. See the lemma
condexpL2_comp_continuousLinearMap for a more general result about commuting with continuous
linear maps.
condexpL2 verifies the equality of integrals defining the conditional expectation.
Alias of MeasureTheory.setLIntegral_nnnorm_condexpL2_indicator_le.
If the measure μ.trim hm is sigma-finite, then the conditional expectation of a measurable set
with finite measure is integrable.
Conditional expectation of the indicator of a measurable set with finite measure, in L2.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Alias of MeasureTheory.setLIntegral_nnnorm_condexpIndSMul_le.
If the measure μ.trim hm is sigma-finite, then the conditional expectation of a measurable set
with finite measure is integrable.
Alias of MeasureTheory.setIntegral_condexpIndSMul.