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Quasi-Isotropic Cycles and Nonsingular Bounces in a Mixmaster Cosmology
Chandrima Ganguly1, Marco Bruni2,3
1Department of Physics and Astronomy, Wilder Laboratories, Dartmouth College, Hanover, New Hampshire 03755, USA.
Physical Review Letters
|December 7, 2019
Summary
This study introduces novel mechanisms for a bouncing, quasi-isotropic mixmaster universe. Negative anisotropic stress smooths chaotic behavior, suggesting an eternal, cyclical universe.
Area of Science:
- Cosmology
- General Relativity
- Theoretical Physics
Background:
- Bianchi type-IX spacetime represents the spatially homogeneous universe.
- The standard model faces challenges with early universe dynamics and homogeneity.
Purpose of the Study:
- To introduce novel mechanisms for nonsingular, quasi-isotropic bounces in a mixmaster universe.
- To explore the role of matter and anisotropic stress in cosmic evolution.
- To investigate the possibility of an eternal, cyclical universe.
Main Methods:
- Utilizing a nonlinear equation of state for matter.
- Introducing negative anisotropic stress to the spacetime.
- Analyzing Einstein's field equations for a Bianchi type-IX metric.
Main Results:
- Nonsingular, quasi-isotropic bounces were achieved through novel mechanisms.
- Negative anisotropic stress effectively isotropized the universe.
- The chaotic mixmaster behavior was significantly mitigated.
- The universe can exist as an eternal series of bouncing cycles.
Conclusions:
- A cyclical universe model is viable, featuring infinite quasi-isotropic bounces.
- Nonlinear matter and negative anisotropic stress are key to a stable, bouncing cosmology.
- This framework offers a potential alternative to standard cosmological models.
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