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Non-geodesic timelike observers and the ultralocal limit.
Reza Saadati1, Luca Valsan2, Valerio Faraoni1
1Department of Physics and Astronomy, Bishop's University, 2600 College Street, Sherbrooke, QC J1M 1Z7 Canada.
The European Physical Journal. C, Particles and Fields
|February 17, 2025
Summary
The ultralocal limit simplifies spacetime geometry for geodesic observers but not for non-geodesic ones. This simplification fails for particles with variable mass or in specific gravity theories.
Area of Science:
- Cosmology
- General Relativity
- Theoretical Physics
Background:
- The ultralocal limit is a theoretical framework simplifying spacetime geometry.
- This limit is known to reduce complex geometries to Bianchi I in specific conditions.
Purpose of the Study:
- To investigate the applicability of the ultralocal limit to non-geodesic timelike observers.
- To identify conditions and specific physical systems where the ultralocal limit does not hold.
Main Methods:
- Analysis of the ultralocal limit's behavior for non-geodesic timelike observers.
- Examination of specific physical scenarios including variable mass particles and scalar-tensor gravity.
Main Results:
- The ultralocal limit does not generally extend to non-geodesic timelike observers.
- Exceptions were identified, including particles with variable mass and test particles in Einstein frame scalar-tensor gravity.
Conclusions:
- The ultralocal limit's applicability is constrained to geodesic observers.
- Further research is needed to fully understand the behavior of non-geodesic observers in various gravitational contexts.
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