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gr-qc2026
Gravitating sources with zero energy density in cosmology
Özgür Akarsu, Cihad Kıbrıs, Burcu Öztürk +1
A cosmological source can have identically zero comoving energy density and still gravitate through its pressure. This differs from an energy density passing through zero at an iso…
gr-qc2026
Defocusing dark energy: Raychaudhuri diagnostics beyond and the phantom divide
Özgür Akarsu, Antonio De Felice, N. Merve Uzun
In general relativity, cosmic acceleration is timelike defocusing of the comoving congruence and requires a negative total active gravitational mass density, $\mathcal{M}_{\rm tot}…