Insights Oppenheimer-Snyder Model of Gravitational Collapse: Implications

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The Oppenheimer-Snyder model describes gravitational collapse using a specific metric that incorporates proper time and radial geodesics. The metric highlights the relationship between the proper time of comoving observers and their respective geodesics, with parameters defining their paths as they approach a singularity. Key elements include the cycloidal time parameter, which indicates the progression of geodesics from initial rest to singularity. The implications of this model extend to understanding the dynamics of collapsing matter and the nature of spacetime during such events. This analysis contributes to the broader understanding of gravitational collapse in astrophysics.
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In the last article in this series, we finished up with a metric for the Oppenheimer-Snyder collapse:
$$
ds^2 = – d\tau^2 + A^2 \left( \eta \right) \left( \frac{dR^2}{1 – 2M \frac{R_-^2}{R_b^2} \frac{1}{R_+}} + R^2 d\Omega^2 \right)
$$
Now we will look at some of the implications of this metric.
First, let’s review what we already know: ##\tau## is the proper time of our comoving observers, who follow radial timelike geodesics starting from mutual rest for all values of ##R## at ##\tau = 0##. ##R## labels each geodesic with its areal radius ##r## at ##\tau = 0##. ##\eta## is a cycloidal time parameter that ranges from ##0## to ##\pi##; ##\eta = 0## is the starting point of each geodesic at ##\tau = 0##, and ##\eta = \pi## is the point at which each geodesic hits the singularity at ##r = 0##. Inside the collapsing matter, ##\eta## is a function of ##\tau##...

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The Poynting vector is a definition, that is supposed to represent the energy flow at each point. Unfortunately, the only observable effect caused by the Poynting vector is through the energy variation in a volume subject to an energy flux through its surface, that is, the Poynting theorem. As a curl could be added to the Poynting vector without changing the Poynting theorem, it can not be decided by EM only that this should be the actual flow of energy at each point. Feynman, commenting...