First model-light constraints on Ω_R + 3Ω_Q from Pantheon+ and BAO reconstructions are consistent with flat FLRW yet too broad to exclude percent-level backreaction.
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On average properties of inhomogeneous fluids in general relativity I: dust cosmologies
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abstract
For general relativistic spacetimes filled with irrotational `dust' a generalized form of Friedmann's equations for an `effective' expansion factor $a_D (t)$ of inhomogeneous cosmologies is derived. Contrary to the standard Friedmann equations, which hold for homogeneous-isotropic cosmologies, the new equations include the `backreaction effect' of inhomogeneities on the average expansion of the model. A universal relation between `backreaction' and average scalar curvature is also given. For cosmologies whose averaged spatial scalar curvature is proportional to $a_D^{-2}$, the expansion law governing a generic domain can be found. However, as the general equations show, `backreaction' acts as to produce average curvature in the course of structure formation, even when starting with space sections that are spatially flat on average.
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A shear-free locally FLRW lattice framework for single-field inflation captures spatially varying expansion, curvature corrections, and nonlinear δN observables at a fraction of the cost of full numerical relativity.
Full-GR simulations find that inhomogeneous curvature produces only sub-dominant systematic offsets in growth-rate measurements from magnitude fluctuations at z ≲ 0.2 relative to current statistical errors.
The fraction of AbacusSummit cosmologies excluded at 3σ by small-scale clustering multipoles drops from 81% to 25% when moving from fixed HOD parameters to broad marginalization over the five-parameter HOD model.
Gaia quasar proper motions show a significant quadrupole signal matching an axisymmetric Bianchi I anisotropy model, but the amplitude does not increase with redshift as the model requires and the inferred local shear exceeds expectations.
Embedding a static Schwarzschild interior into a GCT-FLRW exterior via Israel junction conditions produces a geometric consistency condition that coincides with the GCT background equations.
A sparse population of primordial charged compact objects is hypothesized with specific parameters and shown to face severe plasma-screening and neutralization constraints while failing to produce late-time acceleration in the homogeneous FLRW approximation.
Constraints on primordial charged naked singularities (astrons) show charge saturation and plasma screening limit their viability, with homogeneous energy density scaling as a^{-4} providing no late-time acceleration.
A review summarizing the Hubble constant tension and proposed solutions from new physics that restore agreement between Planck CMB data and local H0 measurements within 1-2 sigma.
citing papers explorer
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A First Observational Assessment of Cosmic Backreaction Over an Extended Redshift Range
First model-light constraints on Ω_R + 3Ω_Q from Pantheon+ and BAO reconstructions are consistent with flat FLRW yet too broad to exclude percent-level backreaction.
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Nonlinear Lattice Framework for Inflation: Bridging stochastic inflation and the $\delta{N}$ formalism
A shear-free locally FLRW lattice framework for single-field inflation captures spatially varying expansion, curvature corrections, and nonlinear δN observables at a fraction of the cost of full numerical relativity.
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Impact of inhomogeneous curvature on growth rate measurements from magnitude fluctuations
Full-GR simulations find that inhomogeneous curvature produces only sub-dominant systematic offsets in growth-rate measurements from magnitude fluctuations at z ≲ 0.2 relative to current statistical errors.
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Bounding the Effect of HOD Assumptions on Small-Scale Clustering Constraints
The fraction of AbacusSummit cosmologies excluded at 3σ by small-scale clustering multipoles drops from 81% to 25% when moving from fixed HOD parameters to broad marginalization over the five-parameter HOD model.
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Mapping the Universe as a Bianchi I cosmology with Gaia data
Gaia quasar proper motions show a significant quadrupole signal matching an axisymmetric Bianchi I anisotropy model, but the amplitude does not increase with redshift as the model requires and the inferred local shear exceeds expectations.
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Geometric Matching of Local Static Regions in Cosmological Spacetimes with an Evolving Lapse
Embedding a static Schwarzschild interior into a GCT-FLRW exterior via Israel junction conditions produces a geometric consistency condition that coincides with the GCT background equations.
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The Case for Astrons
A sparse population of primordial charged compact objects is hypothesized with specific parameters and shown to face severe plasma-screening and neutralization constraints while failing to produce late-time acceleration in the homogeneous FLRW approximation.
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Astrons: Reissner-Nordstr\"om Primordial Naked Singularities
Constraints on primordial charged naked singularities (astrons) show charge saturation and plasma screening limit their viability, with homogeneous energy density scaling as a^{-4} providing no late-time acceleration.
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In the Realm of the Hubble tension $-$ a Review of Solutions
A review summarizing the Hubble constant tension and proposed solutions from new physics that restore agreement between Planck CMB data and local H0 measurements within 1-2 sigma.