Cosmographic Analysis of Dark Energy Models

Cosmographic analysis provides a model-independent framework for characterising the expansion history of the Universe by expressing observable quantities—such as distances and the Hubble rate—as series expansions in redshift. By focusing on kinematic parameters (for example, the deceleration and jerk parameters) rather than on specific dynamical dark energy or modified gravity scenarios, this approach minimises theoretical bias and enables direct tests of cosmic acceleration. Cosmography has been applied to a broad spectrum of data sets, including type Ia supernovae, baryon acoustic oscillations, cosmic microwave background measurements and, more recently, fast radio bursts. Advances in mathematical techniques—such as Padé approximants, Gaussian processes and genetic algorithms—have extended the convergence radius of series expansions and improved reconstruction of higher-order parameters at moderate redshifts. These developments have shed new light on persistent tensions in the Hubble constant, the possible evolution of the dark energy equation of state and the viability of extensions to the standard ΛCDM paradigm. Ongoing work aims to integrate cosmographic constraints with large-scale structure and gravitational-wave standard sirens, offering a coherent, data-driven map of cosmic history without reliance on a predetermined dark energy model.

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Cosmographic Analysis of Dark Energy Models publication trend

The graph below shows the total number of articles in cosmographic analysis of dark energy models across all publications each year (not limited to Nature Index journals).

Technical terms

Cosmography: A model-independent approach that uses series expansions of cosmological observables to describe the Universe’s expansion history without assuming a specific dark energy or gravity model.

Redshift: The fractional increase in the wavelength of light from distant sources due to cosmic expansion, used as a proxy for look-back time.

Deceleration parameter: A dimensionless measure of the second derivative of the scale factor, indicating whether cosmic expansion is accelerating or decelerating at present.

Jerk parameter: A dimensionless descriptor of the third derivative of the scale factor, probing the rate of change of cosmic acceleration.

Luminosity distance: The inferred distance to an object based on the relation between its observed flux and intrinsic luminosity, often expanded in cosmographic series.

Dispersion measure: The integrated column density of free electrons along the line of sight to a fast radio burst, scaling with redshift and serving as a complementary cosmological probe.

Automatic differentiation: A computational method for calculating exact derivatives of complex functions implemented in software, enhancing precision in parameter estimation workflows.

References

1. Analytic auto-differentiable ΛCDM cosmography. Journal of Cosmology and Astroparticle Physics (2023).
2. New generalizations of cosmography inspired by the Padé approximant. European Physical Journal C (2016).
3. Cosmographic Parameters in Model-independent Approaches. The Astrophysical Journal (2021).
4. A measurement of Hubble constant using cosmographic approach combining fast radio bursts and supernovae. Monthly Notices of the Royal Astronomical Society (2023).