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_mul
says that both left and right multiplication are measurable;has_measurable_mul₂
says thatλ p : α × α, p.1 * p.2
is 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.