Heidelberg 2022 – wissenschaftliches Programm

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 3: Black Holes I

AGPhil 3.2: Vortrag

Dienstag, 22. März 2022, 12:00–12:30, AGPhil-H14

Stellar gravitational collapse, singularity formation and theory breakdown — •Kiril Maltsev — Heidelberg Institute for Theoretical Studies / University of Heidelberg

A critical examination of the main physical arguments against the prediction of gravitational singularity formation in stellar core collapse is given, restricted in scope to a historically oriented survey of the decades spanning in between the Schwarzschild 1916 solution and the Penrose 1965 theorem. We first review the 3 definitions (missing point(s), infinite curvature, and geodesic incompleteness) of what a singularity is, and argue that its prediction is problematic for GR, indicating breakdown of Lorentzian geometry, only insofar as infinite curvature is concerned. In contrast, geodesic incompleteness is its innovating hallmark, which is not meaningfully available in Newtonian gravity formulations (infinite density, and infinite gravitational force) of what a gravitational singularity is. The Oppenheimer-Snyder 1939 solution derives the formation of locally infinite curvature and of incomplete geodesics, while Penrose's 1965 theorem concerns the formation of incomplete (null) geodesics only. We assess as the most robust curvature pathology formation counter-argument Markov's derivation of an upper bound on the quadratic curvature invariant from a ratio of natural constants, in connection with Wheeler's conjecture that the Planck scale is ultimate. Finally, we recall Landau's objection to fermionic infinite density point mass formation, which still provides strong reasons to believe that by the least an intermediate state towards the final fate of gravitational collapse must be a bosonic configuration.