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Kinetic Jeans instability in FOG framework
Mritunjoy Das1, Ahmed Atteya2, Pralay Kumar Karmakar3
1Department of Physics, Tezpur University, Napam, Sonitpur, Tezpur, 784028, Assam, India.
Scientific Reports
|March 19, 2026
Summary
The Jeans instability, crucial for cosmic structure formation, is newly modeled using fourth-order gravity. This approach reveals a scale-dependent parameter influencing Jeans mass, potentially explaining structure formation without dark matter or energy.
Area of Science:
- Astrophysics
- Cosmology
- Theoretical Physics
Background:
- Astrophysical structure formation is driven by gravitational (Jeans) instability.
- Recent observations highlight the growth of large-scale structures in the Universe.
Purpose of the Study:
- To propose a kinetic theory-based Jeans instability formalism within the fourth-order gravity (FOG) framework.
- To investigate the impact of a scale-dependent free length parameter (L) from FOG on gravitational instability and structure formation.
Main Methods:
- Utilized the canonical Boltzmann transport equation coupled with the FOG-modified Poisson equation.
- Employed a local normal mode analysis to derive the FOG-modified generalized linear dispersion relation.
- Calculated the critical Jeans mass for various astrophysical clouds.
Main Results:
- Derived a FOG-modified dispersion relation, revealing a non-monotonic density-dependency of Jeans mass at larger L-values.
- Observed that the FOG-modified Jeans mass restricts small-scale collapse while promoting massive fragmentation.
- Demonstrated a smoother formation of large-scale structures without invoking dark energy and dark matter.
Conclusions:
- The FOG-modified Jeans instability offers a novel mechanism for large-scale structure formation.
- This formalism has implications for stellar mass distributions and is supported by astronomical observations.
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