Mimetic Gravity and Cosmological Phenomena

Mimetic gravity is a geometric extension of general relativity that isolates the conformal degree of freedom through a singular conformal transformation, introducing an effective dust-like component that naturally mimics dark matter at cosmological scales. Within this framework, a scalar “mimetic” field can drive early-universe inflation, support late-time acceleration and yield non-singular black hole interiors by smoothing curvature singularities. Multitude of single- and multi-field realisations allows for tailored expansion histories, controlled perturbation spectra and potential links to k-essence or Galileon models. By unifying dark matter and dark energy phenomena under a geometric programme, mimetic gravity offers testable predictions through cosmic microwave background anisotropies, large-scale structure formation and even black hole shadow measurements, highlighting its significance as an alternative avenue for understanding the dark sector and cosmic evolution.

Research from Nature Portfolio

Recent studies have exploited high-resolution imaging of supermassive black hole shadows to test the baseline mimetic gravity framework. Analyses comparing predicted shadow sizes with observations of M87* and Sgr A* reveal inconsistencies: the theory’s solutions yield either no shadow or an unrealistically compact silhouette. These findings effectively rule out the simplest form of mimetic gravity as a viable dark sector model across cosmological scales, underscoring the power of multimessenger astrophysical constraints in assessing modified gravity theories.

Mimetic Gravity and Cosmological Phenomena publication trend

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

Technical terms

Mimetic gravity: A modification of general relativity isolating the conformal degree of freedom to introduce an extra scalar mode that mimics dark matter.

Conformal transformation: A metric rescaling by a scalar function that preserves angles but alters lengths, used to relate auxiliary and physical metrics.

Inflaton: A hypothetical scalar field driving the exponential expansion during cosmic inflation.

Curvaton: An auxiliary scalar field whose isocurvature perturbations convert into adiabatic density fluctuations after inflation.

Black hole shadow: The dark silhouette cast by photon capture around a black hole, whose size and shape are sensitive to the underlying spacetime geometry.

References

1. Mimetic inflation and self-reproduction. Journal of Cosmology and Astroparticle Physics (2023).
2. Extensions of two-field mimetic gravity. Journal of High Energy Physics (2023).
3. Mimetic curvaton. Physical Review D (2023).
4. Event Horizon Telescope observations exclude compact objects in baseline mimetic gravity. Scientific Reports (2024).
5. Mimetic Gravity: A Review of Recent Developments and Applications to Cosmology and Astrophysics. Advances in High Energy Physics (2017).
6. Nonsingular black hole. European Physical Journal C (2017).
7. Mimetic dark matter. Journal of High Energy Physics (2013).