Typeclasses for measurability of operations #
In this file we define classes MeasurableMul etc and prove dot-style lemmas
(Measurable.mul, AEMeasurable.mul etc). For binary operations we define two typeclasses:
MeasurableMulsays that both left and right multiplication are measurable;MeasurableMul₂says thatfun p : α × α => p.1 * p.2is measurable,
and similarly for other binary operations. The reason for introducing these classes is that in case
of topological space α equipped with the Borel σ-algebra, instances for MeasurableMul₂
etc require α to have a second countable topology.
We define separate classes for MeasurableDiv/MeasurableSub
because on some types (e.g., ℕ, ℝ≥0∞) division and/or subtraction are not defined as a * b⁻¹ /
a + (-b).
For instances relating, e.g., ContinuousMul to MeasurableMul see file
MeasureTheory.BorelSpace.
Implementation notes #
For the heuristics of @[to_additive] it is important that the type with a multiplication
(or another multiplicative operations) is the first (implicit) argument of all declarations.
Tags #
measurable function, arithmetic operator
Todo #
- Uniformize the treatment of
powandsmul. - Use
@[to_additive]to sendMeasurablePowtoMeasurableSMul₂. - This might require changing the definition (swapping the arguments in the function that is
in the conclusion of
MeasurableSMul.)
Binary operations: (· + ·), (· * ·), (· - ·), (· / ·) #
- measurable_const_add : ∀ (c : M), Measurable fun x => c + x
- measurable_add_const : ∀ (c : M), Measurable fun x => x + c
We say that a type has MeasurableAdd if (· + c) and (· + c) are measurable functions.
For a typeclass assuming measurability of uncurry (· + ·) see MeasurableAdd₂.
Instances
- measurable_add : Measurable fun p => p.fst + p.snd
We say that a type has MeasurableAdd₂ if uncurry (· + ·) is a measurable functions.
For a typeclass assuming measurability of (c + ·) and (· + c) see MeasurableAdd.
Instances
- measurable_const_mul : ∀ (c : M), Measurable fun x => c * x
- measurable_mul_const : ∀ (c : M), Measurable fun x => x * c
We say that a type has MeasurableMul if (c * ·) and (· * c) are measurable functions.
For a typeclass assuming measurability of uncurry (*) see MeasurableMul₂.
Instances
- measurable_mul : Measurable fun p => p.fst * p.snd
We say that a type has MeasurableMul₂ if uncurry (· * ·) is a measurable functions.
For a typeclass assuming measurability of (c * ·) and (· * c) see MeasurableMul.
Instances
Equations
Equations
A version of measurable_sub_const that assumes MeasurableAdd instead of
MeasurableSub. This can be nice to avoid unnecessary type-class assumptions.
A version of measurable_div_const that assumes MeasurableMul instead of
MeasurableDiv. This can be nice to avoid unnecessary type-class assumptions.
- measurable_pow : Measurable fun p => p.fst ^ p.snd
This class assumes that the map β × γ → β given by (x, y) ↦ x ^ y is measurable.
Instances
Monoid.Pow is measurable.
- measurable_const_sub : ∀ (c : G), Measurable fun x => c - x
- measurable_sub_const : ∀ (c : G), Measurable fun x => x - c
We say that a type has MeasurableSub if (c - ·) and (· - c) are measurable
functions. For a typeclass assuming measurability of uncurry (-) see MeasurableSub₂.
Instances
- measurable_sub : Measurable fun p => p.fst - p.snd
We say that a type has MeasurableSub₂ if uncurry (· - ·) is a measurable functions.
For a typeclass assuming measurability of (c - ·) and (· - c) see MeasurableSub.
Instances
- measurable_const_div : ∀ (c : G₀), Measurable fun x => c / x
- measurable_div_const : ∀ (c : G₀), Measurable fun x => x / c
We say that a type has MeasurableDiv if (c / ·) and (· / c) are measurable functions.
For a typeclass assuming measurability of uncurry (· / ·) see MeasurableDiv₂.
Instances
- measurable_div : Measurable fun p => p.fst / p.snd
We say that a type has MeasurableDiv₂ if uncurry (· / ·) is a measurable functions.
For a typeclass assuming measurability of (c / ·) and (· / c) see MeasurableDiv.
Instances
Equations
Equations
- measurable_neg : Measurable Neg.neg
We say that a type has MeasurableNeg if x ↦ -x is a measurable function.
Instances
- measurable_inv : Measurable Inv.inv
We say that a type has MeasurableInv if x ↦ x⁻¹ is a measurable function.
Instances
Equations
Equations
DivInvMonoid.Pow is measurable.
- measurable_const_vadd : ∀ (c : M), Measurable ((fun x x_1 => x +ᵥ x_1) c)
- measurable_vadd_const : ∀ (x : α), Measurable fun c => c +ᵥ x
We say that the action of M on α has MeasurableVAdd if for each c the map x ↦ c +ᵥ x
is a measurable function and for each x the map c ↦ c +ᵥ x is a measurable function.
Instances
- measurable_const_smul : ∀ (c : M), Measurable ((fun x x_1 => x • x_1) c)
- measurable_smul_const : ∀ (x : α), Measurable fun c => c • x
We say that the action of M on α has MeasurableSMul if for each c the map x ↦ c • x
is a measurable function and for each x the map c ↦ c • x is a measurable function.
Instances
- measurable_vadd : Measurable (Function.uncurry fun x x_1 => x +ᵥ x_1)
We say that the action of M on α has MeasurableVAdd₂ if the map
(c, x) ↦ c +ᵥ x is a measurable function.
Instances
- measurable_smul : Measurable (Function.uncurry fun x x_1 => x • x_1)
We say that the action of M on α has Measurable_SMul₂ if the map
(c, x) ↦ c • x is a measurable function.
Instances
AddMonoid.SMul is measurable.
SubNegMonoid.SMulInt is measurable.
Equations
- AddUnits.instMeasurableSpace = MeasurableSpace.comap AddUnits.val inst
Equations
- Units.instMeasurableSpace = MeasurableSpace.comap Units.val inst
Equations
- IsAddUnit.measurable_const_vadd_iff.match_1 motive hc h_1 = Exists.casesOn hc fun w h => h_1 w h
Instances For
Opposite monoid #
Equations
- AddOpposite.instMeasurableSpace = MeasurableSpace.map AddOpposite.op h
Equations
- MulOpposite.instMeasurableSpace = MeasurableSpace.map MulOpposite.op h
If a scalar is central, then its right action is measurable when its left action is.
If a scalar is central, then its right action is measurable when its left action is.
Big operators: ∏ and ∑ #
Equations
- Finset.aemeasurable_sum'.match_1 s _g motive x h_1 = Exists.casesOn x fun w h => And.casesOn h fun left right => h_1 w left right