Domain of the moment-generating function #
For X a real random variable and μ a finite measure, the set
{t | Integrable (fun ω ↦ exp (t * X ω)) μ} is an interval containing zero. This is the set of
points for which the moment-generating function mgf X μ t is well defined.
We denote that set by integrableExpSet X μ.
We prove the integrability of other functions for t in the interior of that interval.
Main definitions #
ProbabilityTheory.IntegrableExpSet: the interval of reals for whichexp (t * X)is integrable.
Main results #
ProbabilityTheory.integrable_exp_mul_of_le_of_le: ifexp (u * X)is integrable foru = aandu = bthen it is integrable on[a, b].ProbabilityTheory.convex_integrableExpSet:integrableExpSet X μis a convex set.ProbabilityTheory.integrable_exp_mul_of_nonpos_of_ge: ifexp (u * X)is integrable foru ≤ 0then it is integrable on[u, 0].ProbabilityTheory.integrable_rpow_abs_mul_exp_of_mem_interior: forvin the interior of the interval in whichexp (t * X)is integrable, for all nonnegativep : ℝ,|X| ^ p * exp (v * X)is integrable.ProbabilityTheory.memLp_of_mem_interior_integrableExpSet: if 0 belongs to the interior ofintegrableExpSet X μ, thenXis inℒpfor all finitep.
If ω ↦ exp (u * X ω) is integrable at u and -u, then it is integrable on [-u, u].
If ω ↦ exp (u * X ω) is integrable at u ≥ 0, then it is integrable on [0, u].
If ω ↦ exp (u * X ω) is integrable at u ≤ 0, then it is integrable on [u, 0].
The interval of reals t for which exp (t * X) is integrable.
Equations
- ProbabilityTheory.integrableExpSet X μ = {t : ℝ | MeasureTheory.Integrable (fun (ω : Ω) => Real.exp (t * X ω)) μ}
Instances For
integrableExpSet X μ is a convex subset of ℝ (it is an interval).
If exp ((v + t) * X) and exp ((v - t) * X) are integrable, then
ω ↦ exp (t * |X| + v * X) is integrable.
If ω ↦ exp (t * X ω) is integrable at t and -t, then ω ↦ exp (t * |X ω|) is
integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable, then
ω ↦ exp (|t| * |X| + v * X) is integrable.
If ω ↦ exp (t * X ω) is integrable at t and -t, then ω ↦ exp (|t| * |X ω|) is
integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable
then for nonnegative p : ℝ and any x ∈ [0, |t|),
|X| ^ p * exp (v * X + x * |X|) is integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable
then for any n : ℕ and any x ∈ [0, |t|),
|X| ^ n * exp (v * X + x * |X|) is integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable
then for nonnegative p : ℝ, |X| ^ p * exp (v * X) is integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable, then for all n : ℕ,
|X| ^ n * exp (v * X) is integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable, then for all nonnegative p : ℝ,
X ^ p * exp (v * X) is integrable.
If exp ((v + t) * X) and exp ((v - t) * X) are integrable, then for all n : ℕ,
X ^ n * exp (v * X) is integrable.
If ω ↦ exp (t * X ω) is integrable at t and -t for t ≠ 0, then ω ↦ |X ω| ^ p is
integrable for all nonnegative p : ℝ.
If ω ↦ exp (t * X ω) is integrable at t and -t for t ≠ 0, then ω ↦ |X ω| ^ n is
integrable for all n : ℕ. That is, all moments of X are finite.
If ω ↦ exp (t * X ω) is integrable at t and -t for t ≠ 0, then ω ↦ X ω ^ p is
integrable for all nonnegative p : ℝ.
If ω ↦ exp (t * X ω) is integrable at t and -t for t ≠ 0, then ω ↦ X ω ^ n is
integrable for all n : ℕ.
If the interior of the interval integrableExpSet X μ is nonempty,
then X is a.e. measurable.
If v belongs to the interior of the interval integrableExpSet X μ,
then |X| ^ p * exp (v * X) is integrable for all nonnegative p : ℝ.
If v belongs to the interior of the interval integrableExpSet X μ,
then |X| ^ n * exp (v * X) is integrable for all n : ℕ.
If v belongs to the interior of the interval integrableExpSet X μ,
then X ^ p * exp (v * X) is integrable for all nonnegative p : ℝ.
If v belongs to the interior of the interval integrableExpSet X μ,
then X ^ n * exp (v * X) is integrable for all n : ℕ.
If 0 belongs to the interior of the interval integrableExpSet X μ,
then |X| ^ n is integrable for all nonnegative p : ℝ.
If 0 belongs to the interior of the interval integrableExpSet X μ,
then |X| ^ n is integrable for all n : ℕ.
If 0 belongs to the interior of the interval integrableExpSet X μ,
then X ^ n is integrable for all nonnegative p : ℝ.
If 0 belongs to the interior of the interval integrableExpSet X μ,
then X ^ n is integrable for all n : ℕ.
If 0 belongs to the interior of integrableExpSet X μ, then X is in ℒp for all
finite p.