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248 Boolean Analysis — Profile

248.1 Overview

The Gaussian quantile and isoperimetric profile satisfy inverse-function derivative identities, reflection laws, and convexity estimates. The profile extended by zero is continuous, including at the endpoint probabilities.

248.2 Declarations

Lemma 248.1 Strictly increasing Gaussian quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). The function \(Q\) is strictly increasing on \((0,1)\).

Lemma 248.2 Continuity of the Gaussian quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), \(Q\) is continuous at \(a\).

Lemma 248.3 Derivative of the Gaussian quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), \(Q'(a)=1/I(a)\).

Lemma 248.4 Derivative of the Gaussian profile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), \(I'(a)=-Q(a)\).

Lemma 248.5 Derivative of the negative quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), the derivative of \(p\mapsto -Q(p)\) at \(a\) is \(-1/I(a)\).

Lemma 248.6 Evenness of the Gaussian density
✓

The standard Gaussian density satisfies \(\varphi (-x)=\varphi (x)\) for every \(x\in \mathbb R\).

Lemma 248.7 Derivative of the reflected distribution sum
✓

For the standard Gaussian distribution function \(\Phi \), the function \(t\mapsto \Phi (-t)+\Phi (t)\) has derivative zero at every \(x\in \mathbb R\).

Lemma 248.8 Reflection of the Gaussian distribution
✓

The standard Gaussian distribution function satisfies \(\Phi (-x)=1-\Phi (x)\) for every real \(x\).

Lemma 248.9 Complementary Gaussian quantiles
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), \(Q(1-a)=-Q(a)\).

Lemma 248.10 Symmetry of the Gaussian profile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For every \(a\in (0,1)\), \(I(1-a)=I(a)\).

Lemma 248.11 Squared quantile towards the midpoint
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). If \(a,b\in (0,1)\), \(a\le b\), and \(a+b\le 1\), then \(Q(b)^2\le Q(a)^2\).

Lemma 248.12 Profile growth towards the midpoint
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). If \(a,b\in (0,1)\), \(a\le b\), and \(a+b\le 1\), then \(I(a)\le I(b)\).

Lemma 248.13 Convexity of the squared Gaussian quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). The function \(p\mapsto Q(p)^2\) is convex on \((0,1)\).

Lemma 248.14 Derivative of profile times quantile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For \(a\in (0,1)\), the derivative of \(p\mapsto I(p)Q(p)\) at \(a\) is \(1-Q(a)^2\).

Lemma 248.15 Derivative of the squared profile
✓

Let \(\Phi \) and \(\varphi \) be the standard Gaussian distribution function and density, and put \(Q=\Phi ^{-1}\) and \(I(p)=\varphi (Q(p))\) for \(0\lt p\lt 1\). For \(a\in (0,1)\), the derivative of \(p\mapsto I(p)^2\) at \(a\) is \(-2I(a)Q(a)\).

Lemma 248.16 Interior formula for the closed profile
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. If \(a\in (0,1)\), then \(\overline I(a)=\varphi (\Phi ^{-1}(a))\).

Lemma 248.17 Profile at zero
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. Then \(\overline I(0)=0\).

Lemma 248.18 Profile at one
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. Then \(\overline I(1)=0\).

Lemma 248.19 Nonnegativity of the closed profile
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. For every real \(a\), \(\overline I(a)\ge 0\).

Lemma 248.20 Reflection of the closed profile
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. For every real \(a\), \(\overline I(1-a)=\overline I(a)\).

Lemma 248.21 Vanishing profile at the left endpoint
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. Then \(\lim _{p\to 0^+}\overline I(p)=0\).

Lemma 248.22 Continuity at probability zero
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. The function \(\overline I\) is continuous at zero.

Lemma 248.23 Continuity at probability one
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. The function \(\overline I\) is continuous at one.

Lemma 248.24 Interior derivative of the closed profile
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. For \(a\in (0,1)\), \(\overline I'(a)=-\Phi ^{-1}(a)\).

Lemma 248.25 Continuity on the probability interval
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. The function \(\overline I\) is continuous on \([0,1]\).

Lemma 248.26 Continuity of the zero extension
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. The function \(\overline I\) is continuous on \(\mathbb R\).

Lemma 248.27 Integrability of profile compositions
✓

Let \(\Phi ,\varphi \) be the standard Gaussian distribution function and density, and let \(\overline I(p)=\varphi (\Phi ^{-1}(p))\) for \(0\lt p\lt 1\), with \(\overline I(p)=0\) elsewhere. If \(\mu \) is a finite measure on a measurable space \(\Omega \) and \(f:\Omega \to \mathbb R\) is measurable with \(f(x)\in [0,1]\) for every \(x\), then \(\overline I\circ f\) is \(\mu \)-integrable.