Functions integrable on a set and at a filter #
We define IntegrableOn f s μ := Integrable f (μ.restrict s)
and prove theorems like
integrableOn_union : IntegrableOn f (s ∪ t) μ ↔ IntegrableOn f s μ ∧ IntegrableOn f t μ
.
Next we define a predicate IntegrableAtFilter (f : α → E) (l : Filter α) (μ : Measure α)
saying that f
is integrable at some set s ∈ l
and prove that a measurable function is integrable
at l
with respect to μ
provided that f
is bounded above at l ⊓ ae μ
and μ
is finite
at l
.
A function f
is strongly measurable at a filter l
w.r.t. a measure μ
if it is
ae strongly measurable w.r.t. μ.restrict s
for some s ∈ l
.
Equations
- StronglyMeasurableAtFilter f l μ = ∃ s ∈ l, MeasureTheory.AEStronglyMeasurable f (MeasureTheory.Measure.restrict μ s)
Instances For
A function is IntegrableOn
a set s
if it is almost everywhere strongly measurable on s
and if the integral of its pointwise norm over s
is less than infinity.
Equations
- MeasureTheory.IntegrableOn f s μ = MeasureTheory.Integrable f (μ.restrict s)
Instances For
If a function is integrable on a set s
and nonzero there, then the measurable hull of s
is
well behaved: the restriction of the measure to toMeasurable μ s
coincides with its restriction
to s
.
If a function is integrable on a set s
, and vanishes on t \ s
, then it is integrable on t
if t
is null-measurable.
If a function is integrable on a set s
, and vanishes on t \ s
, then it is integrable on t
if t
is measurable.
If a function is integrable on a set s
and vanishes almost everywhere on its complement,
then it is integrable.
If a function is integrable on a set s
and vanishes everywhere on its complement,
then it is integrable.
We say that a function f
is integrable at filter l
if it is integrable on some
set s ∈ l
. Equivalently, it is eventually integrable on s
in l.smallSets
.
Equations
- MeasureTheory.IntegrableAtFilter f l μ = ∃ s ∈ l, MeasureTheory.IntegrableOn f s μ
Instances For
Alias of the forward direction of MeasureTheory.IntegrableAtFilter.inf_ae_iff
.
If μ
is a measure finite at filter l
and f
is a function such that its norm is bounded
above at l
, then f
is integrable at l
.
Alias of MeasureTheory.Measure.FiniteAtFilter.integrableAtFilter_of_tendsto_ae
.
Alias of MeasureTheory.Measure.FiniteAtFilter.integrableAtFilter_of_tendsto
.
If a function converges along a filter to a limit a
, is integrable along this filter, and
all elements of the filter have infinite measure, then the limit has to vanish.
A function which is continuous on a set s
is almost everywhere measurable with respect to
μ.restrict s
.
A function which is continuous on a separable set s
is almost everywhere strongly measurable
with respect to μ.restrict s
.
A function which is continuous on a set s
is almost everywhere strongly measurable with
respect to μ.restrict s
when either the source space or the target space is second-countable.
A function which is continuous on a compact set s
is almost everywhere strongly measurable
with respect to μ.restrict s
.
If a function is continuous on an open set s
, then it is strongly measurable at the filter
𝓝 x
for all x ∈ s
if either the source space or the target space is second-countable.
If a function is continuous on a measurable set s
, then it is measurable at the filter
𝓝[s] x
for all x
.
Lemmas about adding and removing interval boundaries #
The primed lemmas take explicit arguments about the measure being finite at the endpoint, while
the unprimed ones use [NoAtoms μ]
.