Applications of the Hawking Energy in Inhomogeneous Cosmology. (arXiv:2010.07896v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Stock_D/0/1/0/all/0/1">Dennis Stock</a>

The past lightcone of an observer in a cosmological spacetime is the unique
geometric structure directly linked to observations. After general properties
of the Hawking energy along slices of the past lightcone were studied in
arXiv:2003.13583, the present work continues along this path by providing
explicit cosmological applications of the Hawking energy associated with a
lightcone. Firstly, it is shown that amongst all two-dimensional non-trapped
spheres with equal area and average matter density, a shear-free matter
maximizes the Hawking energy for sufficiently high densities. Secondly, a
Robertson-Walker reference slice is constructed for every lightcone slice based
on area and energy. Thirdly, the implications of the monotonicity of the energy
down the lightcone are explored, arriving at two new bounds on the cosmic
fluid’s density and equation-of-state parameter.

The past lightcone of an observer in a cosmological spacetime is the unique
geometric structure directly linked to observations. After general properties
of the Hawking energy along slices of the past lightcone were studied in
arXiv:2003.13583, the present work continues along this path by providing
explicit cosmological applications of the Hawking energy associated with a
lightcone. Firstly, it is shown that amongst all two-dimensional non-trapped
spheres with equal area and average matter density, a shear-free matter
maximizes the Hawking energy for sufficiently high densities. Secondly, a
Robertson-Walker reference slice is constructed for every lightcone slice based
on area and energy. Thirdly, the implications of the monotonicity of the energy
down the lightcone are explored, arriving at two new bounds on the cosmic
fluid’s density and equation-of-state parameter.

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