Improve prop2 proof

This commit is contained in:
2025-06-25 14:37:42 +02:00
parent b18f551a84
commit 1c58c4bf89
2 changed files with 10 additions and 10 deletions

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@@ -1422,25 +1422,25 @@ $$\widehat{\mathcal{R}}_{t,\min} = 2\overline{\widehat{\mathcal{R}}}^{\text{QL}}
First, rewrite $QL_p$ using the check function:
\begin{align}
\rho_p(z) = z(1(0 < z) - p) \label{eq:check}
\rho_p(z) = z(\mathbb{1}(0 < z) - p) \label{eq:check}
\end{align}
\begin{align}
QL_p(x, y) &= (\mathbf1(y < x) - p)(x - y) \\
QL_p(x, y) &= (\mathbb{1}(y < x) - p)(x - y) \\
&= \rho_p(x-y)
\end{align}
Now we can express the quantile risk as:
\begin{align}
\mathcal{Q}_p(x) = E[\rho_p(x-y)] = ∫ \rho_p(x-y)f(y)dy
\mathcal{Q}_p(x) = \mathbb{E}[\rho_p(x-y)] = ∫ \rho_p(x-y)f(y)dy
\end{align}
This integral form is where the convolution becomes apparent. A convolution of functions is defined as:
\begin{align}
(g * h)(x) &= ∫ g(z)h(x - z)dz \\
&= ∫ h(x - z)g(z)dz
&= ∫ g(x - z)h(z)dz
\end{align}
They are commutative.
@@ -1477,7 +1477,7 @@ To find $\mathcal{Q}''_p(x)$ we rewrite \eqref{eq:check}:
The function $\rho'_p(z)$ jumps from $-p$ to $1-p$ at $0$. So:
\begin{align}
\rho''_p(x) = \delta_0(z) \quad \text{Dirac Delta}
\rho''_p(x) = \delta_0(z) \quad \text{(Dirac Delta)}
\end{align}
Now the magical part <i class="fa fa-fw fa-wand-magic-sparkles" style="color:var(--col_amber_6);"></i>: