Big Bang in Dipole Cosmology
arXiv:2307.15791 · doi:10.1140/epjc/s10052-025-13799-6
Abstract
We continue the study of dipole cosmology framework put forward in \cite{Krishnan:2022qbv}, a beyond FLRW setting that has a preferred direction in the metric which may be associated with a cosmological tilt, a cosmic dipole. In this setup the shear and the tilt can be positive or negative given the dipole direction. We thoroughly analyze evolution of the universe in this setting, particularly focusing on the behaviour near the Big Bang (BB). We first analyze a single fluid model with a generic constant equation of state . While details of the behavior near the BB depends on and the other initial conditions, we find that when the shear is negative we have a shear dominated BB singularity, whereas for a positive shear we have a much milder singularity, the whimper singularity \cite{Ellis:1974ug}, at which the tilt blows up while curvature invariants remain finite. We then consider dipole CDM model which besides the shear has two tilt parameters, one for radiation and one for the pressureless matter. For positive (negative) shear we again find whimper (curvature) singularity near the BB. Moreover, when the tilt parameters have opposite signs, the shear can change sign from negative to positive in the course of evolution of the Universe. We show that the relative tilt of the radiation and the matter generically remains sizable at late times.
35 pages, 15 figures, 2 tables
References in corpus (18)
- A Test of the Cosmological Principle with Quasars
- Is the Observable Universe Consistent with the Cosmological Principle?
- Cosmicflows-4
- Analyzing the Large-Scale Bulk Flow using CosmicFlows4: Increasing Tension with the Standard Cosmological Model
- Hints of FLRW Breakdown from Supernovae
- Cosmic Bulk Flow and the Local Motion from Cosmicflows-2
- Directional Variations of Cosmological Parameters from the Planck CMB Data
- Evaluating bulk flow estimators for CosmicFlows-4 measurements
- On the proper kinetic quadrupole CMB removal and the quadrupole anomalies
- Dipole Cosmology: The Copernican Paradigm Beyond FLRW
- Fluid observers and tilting cosmology
- Peculiar motion of Solar system from the Hubble diagram of supernovae Ia and its implications for cosmology
- The deceleration parameter in `tilted' universes: generalising the Friedmann background
- Non-comoving Cosmology
- Evolution of Cyclic Mixmaster Universes with Non-comoving Radiation
- Kinematic and Weyl singularities
- FLRW-Cosmology in Generic Gravity Theories
- Non-comoving Cold Dark Matter in a CDM background