Example：10.1021/acsami.1c06204 or Chem. Rev., 2007, 107, 2411-2502
Mori-Zwanzig Formalism for General Relativity: A New Approach to the Averaging Problem Physical Review Letters (IF9.161), Pub Date : 2021-12-01, DOI: 10.1103/physrevlett.127.231101 Michael te Vrugt, Sabine Hossenfelder, Raphael Wittkowski
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.