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Knot Universes in Bianchi Type I Cosmology
Knot Universes Bianchi Type I Cosmology General Physics
2012/4/19
We investigate the trefoil and figure-eight knot universes from Bianchi-type I cosmology. In particular, we construct several concrete models describing the knot universes related to the cyclic univer...
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.
Expanding universes in the conformal frame of $f(R) $ gravity
Expanding universes conformal frame $f(R) $ gravity
2010/3/17
The late time evolution of Friedmann-Robertson-Walker (FRW) models with a perfect fluid matter source is studied in the conformal frame of $f(R) $ gravity. We assume that the corresponding scalar fiel...
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 ...
In this letter we construct a new time-periodic solution of the vacuum Einstein's ˉeld equations whose Riemann curvature norm takes the inˉnity at some points. We show that this solution is intrinsica...
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...