Brian Jackson edited Ultimately_we_are_interested_in__.tex  over 8 years ago

Commit id: c6b2da7cbef400928c78861fa4a45577a9184784

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Ultimately, we are interested in converting the density of observed parameters to the density of actual parameters, and Equation \ref{eqn:convert_from_actual_to_observed_density} provides a way to do that. Figure \ref{fig:integration_path} illustrates the integration track involved in Equation \ref{fig:integration_path}, and we define the end points of the integration track as $\Gamma_0 \equiv \Gamma_{\rm obs} \left( P_{\rm obs}/P_{\rm min} th}  \right)^{1/2}$ and $\Gamma_1 \equiv \Gamma_{\rm obs} \left( P_{\rm obs}/P_{\rm max} \right)^{1/2}$. The equation involves an integral over $b$, which, given $\Gamma_{\rm obs}$ and $P_{\rm obs}$, represents a fixed curve in $\Gamma_{\rm act}-P_{\rm act}$. In other words, $\Gamma_{\rm obs}$ and $P_{\rm obs}$ define a locus of points for $\Gamma_{\rm act}$ and $P_{\rm act}$, and the integral over $b$ involves traveling along the locus from the point $(\Gamma_{\rm act}, P_{\rm act}) = (\Gamma_{\rm obs}, P_{\rm obs})$ up to $(\Gamma_1, P_{\rm max})$. In fact, any points $(\Gamma_{\rm obs}^\prime, P_{\rm obs}^\prime)$ satisfying Equation \ref{eqn:P_obs_Gamma_obs}, $P_{\rm obs}^\prime\ \Gamma_{\rm obs}^{\prime 2} = P_{\rm obs}\ \Gamma_{\rm obs}^2$, lie on this locus. Consequently, the only difference between $\rho(\Gamma_{\rm obs}^\prime, P_{\rm obs}^\prime)$ and $\rho(\Gamma_{\rm obs}, P_{\rm obs})$ is where on the track the integral starts -- the integrals for both end at the same point.