Conformally Friedmann-Lemaitre-Robertson-Walker cosmologies

Abstract

In a universe where, according to the standard cosmological models, some 97% of the total mass-energy is still "missing in action" it behooves us to spend at least a little effort critically assessing and exploring radical alternatives. Among possible, (dare we say plausible), nonstandard but superficially viable models, those spacetimes conformal to the standard Friedmann-Lemaitre-Robertson-Walker class of cosmological models play a very special role --- these models have the unique and important property of permitting large non-perturbative geometric deviations from Friedmann-Lemaitre-Robertson-Walker cosmology without unacceptably distorting the cosmic microwave background. Performing a "cosmographic" analysis, (that is, temporarily setting aside the Einstein equations, since the question of whether or not the Einstein equations are valid on galactic and cosmological scales is essentially the same question as whether or not dark matter/dark energy actually exist), and using both supernova data and information about galactic structure, one can nevertheless place some quite significant observational constraints on any possible conformal mode --- however there is still an extremely rich range of phenomenological possibilities for both cosmologists and astrophysicists to explore.

V1: 17 pages; V2: 20 pages. 5 references added. Additional comments on local conformal flatness. New section and extra comments comparing/contrasting with LTB, Swiss-cheese, and timescape cosmologies. No physics changes. V3: Now 21 pages. 3 references added. Some additional discussion regarding dynamics. No physics changes. This version accepted for publication in Classical and Quantum Gravity

References in corpus (27)

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Cited by in corpus (29)

• Model-independent reconstruction of $f(Q)$ non-metric gravity
• On the theory and applications of modern cosmography
• High-redshift cosmography: auxiliary variables versus Padé polynomials
• Cosmographic analysis with Chebyshev polynomials
• Rational approximations of $f(R)$ cosmography through Padé polynomials
• Model-independent reconstruction of $f(T)$ teleparallel cosmology
• Model-independent limits and constraints on extended theories of gravity from cosmic reconstruction techniques
• High-redshift cosmography: Application and comparison with different methods
• Revisiting the Hubble constant, spatial curvature and cosmography with time-delay and cosmic chronometer observations
• Constraining extended teleparallel gravity via cosmography: A model-independent approach
• Transit String Dark Energy Models in $f(Q)$ Gravity
• Easing cosmic tensions with an open and hotter universe
• Dark Energy: The Shadowy Reflection of Dark Matter?
• Testing cosmic anisotropy with Pade approximation and Pantheon+ sample
• Redshift remapping and cosmic acceleration in dark-matter-dominated cosmological models
• Gravitational orbits in the expanding universe revisited
• Cosmology in Minkowski space
• Chebyshev cosmography in the framework of extended symmetric teleparallel theory
• Cosmology in Painleve-Gullstrand coordinates
• Joint Constraints on the Hubble Constant, Spatial Curvature, and Sound Horizon from the Late-time Universe with Cosmography
• On the convergence of cosmographic expansions in Lemaitre-Tolman-Bondi models
• Non-perturbative results for the luminosity and area distances
• Bias of reconstructing the dark energy equation of state from the Pad$\acute{e}$ cosmography
• Perturbative treatment of the luminosity distance
• Evolution of Size, Mass, and Density of Galaxies Since Cosmic Dawn
• A semi-cosmographic approach to study cosmological evolution in phase space
• Quintessence dark energy model in non-linear $f(Q)$ theory with bulk-viscosity
• Missing Components in ΛCDM from DESI Y1 BAO Measurements: Insights from Redshift Remapping
• The dynamics of background evolution and structure formation in phase space: a semi-cosmographic reconstruction