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Landau PDF

Landau PDF

:::: {.columns} ::: {.column width=50% align=center}

$$
  L(x) = \frac{1}{\pi} \int \limits_{0}^{+ \infty}
         dt \, e^{-t \ln(t) -xt} \sin (\pi t)

:::

::: {.column width=50%} ::: ::::

. . .

No closed form for \textcolor{cyclamen}{ANYTHING}

Landau median

The median of a PDF is defined as:


  m = Q \left( \frac{1}{2} \right)

. . .

  • CDF computed by numerical integration
  • QDF computed by numerical root-finding (Brent)

\setbeamercovered{}

\begin{center} \begin{tikzpicture}[remember picture] \node at (0,0) (here) {$m_L\ex = 1.3557804...$}; \pause \node [opacity=0.5, xscale=0.35, yscale=0.25 ] at (here) {\includegraphics{images/high.png}}; \end{tikzpicture} \end{center}

\setbeamercovered{transparent}

Landau mode

  • Maximum \hence \partial_x L(\mu) = 0

. . .

  • Computed by numerical minimization (Brent)

\setbeamercovered{}

\begin{center} \begin{tikzpicture}[remember picture] \node at (0,0) (here) {$\mu_L\ex = 0.22278...$}; \pause \node [opacity=0.5, xscale=0.32, yscale=0.25 ] at (here) {\includegraphics{images/high.png}}; \end{tikzpicture} \end{center}

\setbeamercovered{transparent}

Landau FWHM

We need to compute the maximum:


  L_{\text{max}} = L(\mu_L)

  \text{FWHM} = w = x_+ - x_- \with L(x_{\pm}) = \frac{L_{\text{max}}}{2}

. . .

  • Computed by numerical root finding (Brent)

\setbeamercovered{}

\begin{center} \begin{tikzpicture}[remember picture] \node at (0,0) (here) {$w_L\ex = 4.018645...$}; \pause \node [opacity=0.5, xscale=0.32, yscale=0.25 ] at (here) {\includegraphics{images/high.png}}; \end{tikzpicture} \end{center}

\setbeamercovered{transparent}