How isotropic is the Universe?

Abstract

A fundamental assumption in the standard model of cosmology is that the Universe is isotropic on large scales. Breaking this assumption leads to a set of solutions to Einstein's field equations, known as Bianchi cosmologies, only a subset of which have ever been tested against data. For the first time, we consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck. For the vector mode (associated with vorticity), we obtain a limit on the anisotropic expansion of $({\sigma }_V/H{)}_0<4.7\times 10^{-11}$ (95% CI), which is an order of magnitude tighter than previous Planck results that used CMB temperature only. We also place upper limits on other modes of anisotropic expansion, with the weakest limit arising from the regular tensor mode, $({\sigma }_{T,\mathrm{reg}}/H{)}_0<1.0\times 10^{-6}$ (95% CI). Including all degrees of freedom simultaneously for the first time, anisotropic expansion of the Universe is strongly disfavoured, with odds of 121,000:1 against.

6 pages, 1 figure, v2: replaced with version accepted by PRL

References in corpus (18)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Efficient Computation of CMB anisotropies in closed FRW models
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• Multimodal nested sampling: an efficient and robust alternative to MCMC methods for astronomical data analysis
• PolyChord: nested sampling for cosmology
• PolyChord: next-generation nested sampling
• Evidence of vorticity and shear at large angular scales in the WMAP data: a violation of cosmological isotropy?
• Planck 2013 results. XXVI. Background geometry and topology of the Universe
• How Anisotropic is our Universe?
• Bianchi Model CMB Polarization and its Implications for CMB Anomalies
• Limits to Global Rotation and Shear From the COBE DMR 4-Year Sky Maps
• Markov chain Monte Carlo analysis of Bianchi VII_h models
• The cut-sky cosmic microwave background is not anomalous
• Rogues' gallery: the full freedom of the Bianchi CMB anomalies
• Linearization of homogeneous, nearly-isotropic cosmological models
• Bayesian analysis of anisotropic cosmologies: Bianchi VII_h and WMAP
• A framework for testing isotropy with the cosmic microwave background

Cited by in corpus (92)

• Teleparallel Gravity: From Theory to Cosmology
• Is the Observable Universe Consistent with the Cosmological Principle?
• Constraints on a Bianchi type I spacetime extension of the standard $\Lambda$CDM model
• Hints of a Local Matter Underdensity or Modified Gravity in the Low $z$ Pantheon data
• Cosmological parameter inference with Bayesian statistics
• Testing spatial curvature and anisotropic expansion on top of the $\Lambda$CDM model
• Cosmological models with a hybrid scale factor in an extended gravity theory
• Cosmological inference from Bayesian forward modelling of deep galaxy redshift surveys
• Bianchi-V String Cosmological model with Dark Energy Anisotropy
• Stability of the Kasner Universe in f(T) Gravity
• Anisotropic cosmological reconstruction in $f(R,T)$ gravity
• Geodesic-light-cone coordinates and the Bianchi I spacetime
• Screening anisotropy via energy-momentum squared gravity: $\Lambda$CDM model with hidden anisotropy
• Anisotropic stars in modified gravity: An extended gravitational decoupling approach
• Bumblebee field as a source of cosmological anisotropies
• Physical validity of anisotropic models derived from isotropic fluid dynamics in $f(R,T)$ theory: An implication of gravitational decoupling
• Polypolar spherical harmonic decomposition of galaxy correlators in redshift space: Toward testing cosmic rotational symmetry
• Numerical simulations of stochastic inflation using importance sampling
• Decoupled Anisotropic Buchdahl's Relativistic Models in $f(\mathbb{R},\mathbb{T})$ Theory
• Dynamical systems analysis of $f(Q)$ gravity
• Anisotropic Einstein Yang-Mills Higgs Dark Energy
• Anisotropic massive Brans-Dicke gravity extension of the standard $\Lambda$CDM model
• Dynamical features of an anisotropic cosmological model
• The quadrupole in the local Hubble parameter: first constraints using Type Ia supernova data and forecasts for future surveys
• Accelerating models with a hybrid scale factor in extended gravity
• Cosmological dynamical systems in modified gravity
• Are stellar--mass binary black hole mergers isotropically distributed?
• Stealth magnetic field in de Sitter spacetime
• Non-comoving Cosmology
• Two fluid anisotropic dark energy models in a scale invariant theory
• \bf $\delta M$ Formalism: A New Approach to Cosmological Perturbation Theory in Anisotropic Inflation
• Space-time second-quantization effects and the quantum origin of cosmological constant in covariant quantum gravity
• Anisotropic power-law inflation for a conformal-violating Maxwell model
• Anisotropic constant-roll inflation for the Dirac-Born-Infeld model
• A nonsingular, anisotropic universe in a black hole with torsion and particle production
• Correlated orientations of the axes of large quasar groups on Gpc scales
• Quasi-isotropic cycles and non-singular bounces in a Mixmaster cosmology
• Anisotropic power-law inflation for a model of two scalar and two vector fields
• Bianchi I metric solutions with nonminimally coupled Einstein-Maxwell gravity theory
• Bianchi cosmologies with $p$-form gauge fields
• Anisotropic Scalar Field Dark Energy with a Disformally Coupled Yang-Mills Field
• Investigating the physical and geometrical parameters of the cosmological models with anisotropic background
• Structure formation in an anisotropic universe: Eulerian perturbation theory
• Stable small spatial hairs in a power-law k-inflation model
• Bianchi spacetimes as super-curvature modes around isotropic cosmologies
• CMB imprints of non-canonical anisotropic inflation
• A Novel CMB Component Separation Method: Hierarchical Generalized Morphological Component Analysis
• Two-point Correlation Functions in Inhomogeneous and Anisotropic Cosmologies
• Dark Energy From Dynamical Projective Connections
• Bianchi-I cosmology from causal thermodynamics
• Stability, dark energy parameterization and swampland aspect of Bianchi Type-$V{I}_h$ cosmological models with f(R, T)-gravity
• Stability analysis of two-fluid dark energy models
• Probing the Cosmological Principle with weak lensing shear
• Cosmological fluids with boundary term couplings
• Modelling the emergence of cosmic anisotropy from non-linear structures
• Anisotropic hyperbolic inflation for a model of two scalar and two vector fields
• Observational constraints on anisotropies for bouncing alternatives to inflation
• New Anisotropic Exact Solution in Multifield Cosmology
• Late-Time Anisotropy Sourced by a 2-Form Field Non-Minimally Coupled to Cold Dark Matter
• Spatially Homogeneous Universes with Late-Time Anisotropy
• Scrutinizing coupled vector dark energy in light of data
• Dynamical analysis of a first order theory of bulk viscosity
• $\Lambda$CDM cosmology with a quiescent anisotropy in a higher dimensional steady state universe
• Testing time-delayed cosmology
• Raychaudhuri-based reconstruction of anisotropic Einstein-Maxwell equation in 1+3 covariant formalism of $f(R)$-gravity
• Spinning Toroidal Brane Cosmology; A Classical and Quantum Survey
• Magnetic Bianchi-I cosmology in the Horndeski theory
• Quantum Mechanics from General Relativity and the Quantum Friedmann Equation
• The rotation problem
• Domain Wall Bianchi Type $V{I}_0$ Universe in $f(R,T)$ Gravity
• The Cosmic Causal Mass
• Multifield curved solid: Early dark energy and perturbation instabilities
• Cosmic no-hair theorems for viscous contracting Universes
• Galaxy infall models for arbitrary velocity directions
• Exact cosmological solutions with magnetic field in the theory of gravity with non-minimal kinetic coupling
• Gravitation and cosmology with York time
• Ricci cosmology in light of astronomical data
• Bianchi cosmologies in a Thurston-based theory of gravity
• The Cosmological Dipole in Tilted Anisotropic Universes
• An approximate application of quantum gravity to the rotation problem
• Probing the Cosmological Principle with CMB lensing and cosmic shear
• CMB line-of-sight integrators for nearly-isotropic cosmological models
• Stability Analysis of Four $f(Q)$ Gravity Models : A Cosmological Review in the Background of Bianchi-I Anisotropy
• Space-Time Entropy, Space of Singularities and Gravity Origin: A Case Study
• States of Low Energy on Bianchi I spacetimes
• The oscillatory anisotropy in the spatially flat cosmological models
• Primordial Magnetogenesis from Killing Vector Fields
• Origin & evolution of the Universe
• Lorentzian Vacuum Transitions for Anisotropic Universes
• An effective fluid description of scalar-vector-tensor theories under the sub-horizon and quasi-static approximations
• Cosmological models with Big rip and Pseudo rip Scenarios in extended theory of gravity
• Anisotropic constant-roll k-inflation model