The one-variable p-biased inequality from a pointwise bound
DefinitionMean of a p-biased two-valued function#✓fully proved
The mean (1-p) + p z of the p-biased two-valued function with values 1 and z.
def pih_m (p z : ℝ) : ℝ := (1 - p) + p * z
DefinitionVariance term in the p-biased inequality#✓fully proved
The variance term 4(q-1) p²(1-p)²(z - 1)².
def pih_V (p q z : ℝ) : ℝ := 4 * (q - 1) * p ^ 2 * (1 - p) ^ 2 * (z - 1) ^ 2
DefinitionPointwise bound behind the p-biased inequality#✓fully proved
The pointwise bound (q/2) m^(q-2) V ≤ (1-p) + p z^q - m^q for all z ≥ 0, with
m = pih_m p z, V = pih_V p q z.
def pih_KEY (p q : ℝ) : Prop :=
∀ z : ℝ, 0 ≤ z →
(q / 2) * (pih_m p z) ^ (q - 2) * pih_V p q z ≤ (1 - p) + p * z ^ q - (pih_m p z) ^ q
def pih_m (p z : ℝ) : ℝ := (1 - p) + p * z
MathlibExt/Probability/Hypercontractivity/PBiasedIntegralHC.lean:45
def pih_V (p q z : ℝ) : ℝ := 4 * (q - 1) * p ^ 2 * (1 - p) ^ 2 * (z - 1) ^ 2
MathlibExt/Probability/Hypercontractivity/PBiasedIntegralHC.lean:48
TheoremPointwise bound implies the one-variable p-biased inequality#✓fully proved
The pointwise bound pih_KEY p q implies the one-variable inequality pbt_OneVarCore p q.
theorem pih_core_of_KEY {p q : ℝ} (hp0 : 0 < p) (hp1 : p < 1) (hq1 : 1 ≤ q) (hq2 : q ≤ 2)
(HKEY : pih_KEY p q) : pbt_OneVarCore p q
def pih_KEY (p q : ℝ) : Prop :=
∀ z : ℝ, 0 ≤ z →
(q / 2) * (pih_m p z) ^ (q - 2) * pih_V p q z ≤ (1 - p) + p * z ^ q - (pih_m p z) ^ q
MathlibExt/Probability/Hypercontractivity/PBiasedIntegralHC.lean:55
def pbt_OneVarCore (p q : ℝ) : Prop :=
∀ z : ℝ, 0 ≤ z → pbt_g p q z ≤ ((1 - p) + p * z ^ q) ^ (2 / q)
MathlibExt/Probability/Hypercontractivity/PBiasedTwoPoint.lean:55
Theoremp-biased two-point inequality from the pointwise bound#✓fully proved
The p-biased two-point inequality from pih_KEY p q and pih_KEY (1 - p) q.
theorem pih_two_point_value_of_KEY {p q : ℝ} (hp0 : 0 < p) (hp1 : p < 1)
(hq1 : 1 ≤ q) (hq2 : q ≤ 2)
(HKEY : pih_KEY p q) (HKEY' : pih_KEY (1 - p) q) (u v : ℝ) :
((1 - p) * u + p * v) ^ 2 + (q - 1) * 4 * p ^ 2 * (1 - p) ^ 2 * (u - v) ^ 2
≤ ((1 - p) * |u| ^ q + p * |v| ^ q) ^ (2 / q)
def pih_KEY (p q : ℝ) : Prop :=
∀ z : ℝ, 0 ≤ z →
(q / 2) * (pih_m p z) ^ (q - 2) * pih_V p q z ≤ (1 - p) + p * z ^ q - (pih_m p z) ^ q
MathlibExt/Probability/Hypercontractivity/PBiasedIntegralHC.lean:55
Uses 4 · Used by 1
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