Modified Gravity Models in Cosmological Evolution

Modified gravity models seek to extend or alter Einstein’s theory of general relativity in order to explain key cosmological phenomena—most notably the accelerated expansion of the universe—without invoking an unknown dark energy component. Among the most extensively studied frameworks are f(R) theories, in which the Ricci scalar R in the gravitational action is replaced by a function f(R), and scalar-tensor models that introduce one or more dynamical scalar fields coupled to curvature. Such constructions can yield both an inflationary epoch at early times and a late-time de Sitter attractor, offering a unified geometrical description of cosmic history. Central to these approaches are screening mechanisms—such as the chameleon effect—that ensure consistency with solar-system tests while allowing deviations from the standard model on large scales. Observational constraints derive from distances to type Ia supernovae, measurements of baryon acoustic oscillations (BAO), cosmic microwave background anisotropies and Hubble parameter determinations via cosmic chronometers. The study of deviation parameters, transition redshift and the effective equation of state provides a means to compare modified gravity scenarios against the concordance ΛCDM model. By confronting models with precision data, researchers probe whether modifications of gravity can alleviate tensions such as the discrepancy in local and global determinations of the Hubble constant, and whether they can reproduce the growth of structure in agreement with large-scale surveys. The global significance of this programme lies in its potential to reveal new gravitational physics, deepen our understanding of fundamental interactions and shape the next generation of cosmological tests.

Research from Nature Portfolio

No recent Nature Portfolio content available.

Modified Gravity Models in Cosmological Evolution publication trend

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

Technical terms

f(R) gravity: A class of theories in which the Ricci scalar R in the Einstein–Hilbert action is replaced by a general function f(R), introducing additional scalar degrees of freedom.

ΛCDM model: The standard cosmological paradigm comprising a cosmological constant (Λ) and cold dark matter (CDM), against which alternative theories are tested.

Baryon Acoustic Oscillations: Regular, periodic fluctuations in the density of visible baryonic matter that serve as a standard ruler for cosmological distance measurements.

Cosmic chronometers: A technique for estimating the Hubble parameter H(z) through differential age measurements of passively evolving galaxies.

Equation of state parameter: The ratio of pressure to energy density (w = p/ρ) of a cosmic component, used to characterise its dynamical behaviour.

Hubble tension: The discrepancy between the value of the Hubble constant H₀ measured locally (e.g. by supernovae) and that inferred from the cosmic microwave background.

Early dark energy: A hypothetical component that contributes non-negligibly to the total energy budget at early times, potentially affecting CMB and H₀ estimates.

References

1. f(R) gravity modifications: from the action to the data. European Physical Journal C (2018).
2. Investigating the accelerated expansion of the Universe through updated constraints on viable f(R) models within the metric formalism. Monthly Notices of the Royal Astronomical Society (2023).
3. Viability tests of f(R)-gravity models with Supernovae Type 1A data. European Physical Journal C (2020).
4. Analyzing the H 0 tension in F(R) gravity models. Nuclear Physics B (2021).