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On Shear-Free perturbations of FLRW Universes
On Shear-Free perturbations of FLRW Universes
2011/10/14
A surprising exact result for the Einstein Field Equations is that if pressure-free matter is moving in a shear-free way, then it must be either expansion-free or rotation-free. It has been suggested ...
Light propagation and the average expansion rate in near-FRW universes
Light propagation average expansion rate universes
2011/9/29
We consider universes which are close to Friedmann-Robertson-Walker in the sense that metric perturbations, their time derivatives and first spatial derivatives are small, but second spatial derivativ...
A Note on the Inverse Problem with LTB Universes
Cosmology and Extragalactic Astrophysics (astro-ph.CO) General Relativity and Quantum Cosmology (gr-qc)
2010/12/23
The inverse problem with Lema\^itre-Tolman-Bondi (LTB) universe models is discussed. The LTB solution for the Einstein equations describes the spherically symmetric dust-filled spacetime. The LTB solu...
Redshift Drift in LTB Void Universes
Cosmology and Extragalactic Astrophysics (astro-ph.CO)
2010/12/23
We study the redshift drift, i.e., the time derivative of the cosmological redshift in the Lema\^itre-Tolman-Bondi (LTB) solution in which the observer is assumed to be located at the symmetry center.
HOW MANY UNIVERSES ARE NECESSARY FOR AN ICE CREAM TO MELT?
cosmology theory-gravitation-history and philosophy of astronomy
2009/3/13
We investigate a quantitative consequence of the Acausal-Anthropic
approach to solving the long-standing puzzle of the thermodynamical arrow
of time. Notably, the size of the required multiverse is ...
The dynamics of closed LFRW universes with a massive inflaton field is examined where Friedmann equations are corrected by the introduction of a potential term arising from quantum gravity corrections...