Inhomogeneous Cosmological Models and Dynamics

Conventional cosmology rests on the assumption of large-scale homogeneity and isotropy as enshrined in the Friedmann–Lemaître–Robertson–Walker framework. Inhomogeneous cosmological models relax this idealisation by permitting spatial variations in matter density and curvature, thereby offering a richer description of the Universe’s structure and evolution. Such models are indispensable for probing the impact of voids, filaments and superclusters on observable quantities, from luminosity–distance relations to cosmic microwave background anisotropies. By employing exact solutions to Einstein’s equations, notably the Lemaître–Tolman–Bondi and Szekeres families, researchers can assess backreaction effects that arise when averaging localised inhomogeneities over cosmological scales. These effects have been invoked in discussions of apparent accelerated expansion and the Hubble tension, and they provide a platform for testing alternative scenarios to dark energy. Dynamics within inhomogeneous frameworks encompass the growth of structure under general relativistic gravity, the peculiar velocities of cold dark matter, and the interplay between anisotropy and quantum corrections in the early Universe. Recent advances have also explored the role of Weyl curvature in encoding gravitational entropy and examined whether quantum potential terms can induce pressure in otherwise silent spacetimes. Collectively, these developments deepen our understanding of how non-uniform distributions of matter and geometry shape the cosmic expansion history and inform the interpretation of precision observations.

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Inhomogeneous Cosmological Models and Dynamics publication trend

The graph below shows the total number of articles in inhomogeneous cosmological models and dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

Inhomogeneous cosmological model: A solution of Einstein’s equations allowing spatial variation in matter density and curvature rather than exact uniformity.

Lemaître–Tolman–Bondi model (LTB): An exact spherically symmetric dust solution used to describe radial inhomogeneities in an expanding Universe.

Szekeres model: A family of exact, generally anisotropic, inhomogeneous dust solutions without any symmetry requirement, capable of modelling structures such as voids and filaments.

Coarse-graining: The process of averaging small-scale inhomogeneities to derive an effective large-scale description of the geometry and matter distribution.

Quantum potential: A term arising in the de Broglie–Bohm formulation of quantum mechanics that can modify classical dynamical equations and introduce effective pressure or anisotropy.

References

1. Cosmic spherical void via coarse-graining and averaging non-spherical structures. Physics Letters B (2011).
2. An exploration of the black hole entropy via the Weyl tensor. European Physical Journal C (2016).
3. Non-comoving cold dark matter in a ΛCDM background. European Physical Journal C (2021).
4. Quantum Potentiality in Inhomogeneous Cosmology. Universe (2021).