Cosmological Models and Theories of Gravity

The modern description of the Universe is founded upon general relativity and the Friedmann–Lemaître–Robertson–Walker (FRW) class of solutions, in which a cosmological constant or dark‐energy component drives accelerated expansion. The concordance ΛCDM model has proved remarkably successful in accounting for cosmic microwave background anisotropies, large‐scale structure and type Ia supernova observations, yet outstanding tensions in the Hubble parameter and the nature of dark components have motivated alternative frameworks. These include extensions of Einstein’s equations in which the gravitational Lagrangian is a general function of curvature invariants—such as in f(R) or f(R,T) theories—or of torsion, as in f(T) gravity. Scalar–tensor constructions introduce supplementary fields to mediate gravitational interactions, while anisotropic Bianchi models explore departures from strict homogeneity in the early Universe. Higher‐dimensional scenarios and approaches inspired by quantum gravity attempt to reconcile microscopic physics with cosmic evolution. Together, these models offer new tests of fundamental physics through observations of cosmic expansion, gravitational waves and structure formation, illuminating both the earliest epochs and the ultimate fate of the cosmos.

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Cosmological Models and Theories of Gravity publication trend

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

Technical terms

f(R,T) theory of gravity: A modification of general relativity in which the gravitational action depends on the Ricci scalar R and the trace of the stress–energy tensor T, allowing for nonminimal matter–geometry coupling.

f(T) gravity: An alternative gravity theory formulated in the teleparallel framework, where T is the torsion scalar and the action is a general function of T, leading to second‐order field equations.

Torsion scalar (T): In teleparallel gravity, a scalar quantity built from the torsion tensor that characterises gravitational interactions via spacetime torsion rather than curvature.

Friedmann–Lemaître–Robertson–Walker (FRW) model: A class of cosmological solutions assuming spatial homogeneity and isotropy, described by a scale factor that governs expansion.

Bianchi type I model: The simplest anisotropic cosmology, generalising the FRW metric by allowing different scale factors along orthogonal spatial axes.

Deceleration parameter (q): A dimensionless measure of cosmic acceleration defined by q = –(ä/a)/(ḋa/a)², where a is the scale factor; negative values indicate acceleration.

References

1. Perfect Fluid with Heat Flow in f(T) Theory of Gravity. East European Journal of Physics (2024).
2. A Transition Model in f(R,T) Theory via Observational Constraints. Symmetry (2023).