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arXiv · 2107.11497

Mori-Zwanzig formalism for general relativity: a new approach to the averaging problem

Michael te Vrugt·Sabine Hossenfelder·Raphael Wittkowski
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Abstract

Cosmology relies on a coarse-grained description of the universe, assumed to be valid on large length scales. However, the nonlinearity of general relativity makes coarse-graining extremely difficult. We here address this problem by extending the Mori-Zwanzig projection operator formalism, a highly successful coarse-graining method from statistical mechanics, towards general relativity. Using the Buchert equations, we derive a new dynamic equation for the Hubble parameter which captures the effects of averaging through a memory function. This gives an empirical prediction for the cosmic jerk.

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Michael te Vrugt, Sabine Hossenfelder, Raphael Wittkowski. 2021-07-24. Mori-Zwanzig formalism for general relativity: a new approach to the averaging problem. https://doi.org/10.1103/physrevlett.127.231101

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