Symbol phi

The passage around this formula

…own location, so a network’s fitted node potential can be compared against a measurement made over any convenient physical route without first specifying which route was used. Define the dimensionless node potential $\phi(\mathbf x)$ := $\ln$ U($\mathbf x$) and the edge observable actually recorded between linked clocks i and j , $y_{ij} := \ln(\nu_j/\nu_i) = \phi(\mathbf x_i) - \phi(\mathbf x_j)$. At weak field this reduces to the familiar $y_{ij}$ $\approx$ ($\Phi_i$ - $\Phi_j$)/$c^2$ for Newtonian potential $\Phi$ , exactly the quantity real fibre-linked clock comparisons…

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