Typeclasses for measurability of operations #
In this file we define classes has_measurable_mul etc and prove dot-style lemmas
(measurable.mul, ae_measurable.mul etc). For binary operations we define two typeclasses:
has_measurable_mulsays that both left and right multiplication are measurable;has_measurable_mul₂says thatλ 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 has_measurable_mul₂
etc require α to have a second countable topology.
We define separate classes for has_measurable_div/has_measurable_sub
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., has_continuous_mul to has_measurable_mul see file
measure_theory.borel_space.
Tags #
measurable function, arithmetic operator
Binary operations: (+), (*), (-), (/) #
- measurable_const_add : ∀ (c : M), measurable (has_add.add c)
- measurable_add_const : ∀ (c : M), measurable (λ (_x : M), _x + c)
We say that a type has_measurable_add if ((+) c) and (+ c) are measurable functions.
For a typeclass assuming measurability of uncurry (+) see has_measurable_add₂.
- measurable_add : measurable (λ (p : M × M), p.fst + p.snd)
We say that a type has_measurable_add if uncurry (+) is a measurable functions.
For a typeclass assuming measurability of ((+) c) and (+ c) see has_measurable_add.
Instances
- measurable_const_mul : ∀ (c : M), measurable (has_mul.mul c)
- measurable_mul_const : ∀ (c : M), measurable (λ (_x : M), _x * c)
We say that a type has_measurable_mul if ((*) c) and (* c) are measurable functions.
For a typeclass assuming measurability of uncurry (*) see has_measurable_mul₂.
- measurable_mul : measurable (λ (p : M × M), (p.fst) * p.snd)
We say that a type has_measurable_mul if uncurry (*) is a measurable functions.
For a typeclass assuming measurability of ((*) c) and (* c) see has_measurable_mul.
- measurable_pow : measurable (λ (p : β × γ), p.fst ^ p.snd)
This class assumes that the map β × γ → β given by (x, y) ↦ x ^ y is measurable.
Equations
- measurable_const_sub : ∀ (c : G), measurable (λ (x : G), c - x)
- measurable_sub_const : ∀ (c : G), measurable (λ (x : G), x - c)
We say that a type has_measurable_sub if (λ x, c - x) and (λ x, x - c) are measurable
functions. For a typeclass assuming measurability of uncurry (-) see has_measurable_sub₂.
- measurable_sub : measurable (λ (p : G × G), p.fst - p.snd)
We say that a type has_measurable_sub if uncurry (-) is a measurable functions.
For a typeclass assuming measurability of ((-) c) and (- c) see has_measurable_sub.
- measurable_const_div : ∀ (c : G₀), measurable (has_div.div c)
- measurable_div_const : ∀ (c : G₀), measurable (λ (_x : G₀), _x / c)
We say that a type has_measurable_div if ((/) c) and (/ c) are measurable functions.
For a typeclass assuming measurability of uncurry (/) see has_measurable_div₂.
- measurable_div : measurable (λ (p : G₀ × G₀), p.fst / p.snd)
We say that a type has_measurable_div if uncurry (/) is a measurable functions.
For a typeclass assuming measurability of ((/) c) and (/ c) see has_measurable_div.
Instances
- measurable_neg : measurable has_neg.neg
We say that a type has_measurable_neg if x ↦ -x is a measurable function.
Instances
- measurable_inv : measurable has_inv.inv
We say that a type has_measurable_inv if x ↦ x⁻¹ is a measurable function.
Equations
- has_measurable_gpow G = let _inst : measurable_singleton_class ℤ := has_measurable_gpow._proof_1 in {measurable_pow := _}
- measurable_const_smul : ∀ (c : M), measurable (has_scalar.smul c)
- measurable_smul_const : ∀ (x : α), measurable (λ (c : M), c • x)
We say that the action of M on α has_measurable_smul 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.
- measurable_smul : measurable (function.uncurry has_scalar.smul)
We say that the action of M on α has_measurable_smul if the map
(c, x) ↦ c • x is a measurable function.