Disformal transformations of Friedmann-Lema^itre-Robertson-Walker and
Bianchi geometries are analyzed in the context of scalar-tensor gravity. Novel
aspects discussed are the $3+1$ splitting, the effective fluid equivalent of
the gravitational scalar, Bianchi models, stealth solutions and de Sitter
solutions with non-constant scalar field (which are signatures of scalar-tensor
gravity). Both pure disformal transformations and more general ones are
discussed.

Conclusions

In this article, we have examined the implications of disformal transformations in the context of scalar-tensor gravity. We have analyzed their effects on Friedmann-Lema^itre-Robertson-Walker and Bianchi geometries. The novel aspects discussed include the +1$ splitting, the effective fluid equivalent of the gravitational scalar, and the existence of stealth solutions and de Sitter solutions with non-constant scalar field, which are unique to scalar-tensor gravity.

We have also explored both pure disformal transformations and more general ones, highlighting their significance in understanding the dynamics of the universe. These transformations provide a new perspective on the connection between geometry and gravity, shedding light on potential modifications to the standard models of cosmology.

Future Roadmap

Potential Challenges:

  1. Experimental Validation: One of the key challenges in further studying disformal transformations in scalar-tensor gravity is experimental validation. It is crucial to design experiments or observations that can test and confirm the predictions made by these theoretical analyses.
  2. Theoretical Refinements: Exploring more complex and realistic scenarios, such as incorporating matter fields and other interactions, will require further theoretical refinements. Developing appropriate mathematical frameworks to account for these complexities is a challenge that researchers will need to tackle.
  3. Data Analysis: As more observational data becomes available, it will be important to develop sophisticated data analysis techniques to extract meaningful insights from the observed signatures of scalar-tensor gravity and disformal transformations.

Potential Opportunities:

  • Cosmological Consequences: Further investigation of disformal transformations in scalar-tensor gravity may uncover new cosmological consequences and provide a deeper understanding of the evolution and structure of the universe.
  • Modified Gravity Theories: The insights gained from studying disformal transformations may contribute to the development of modified gravity theories, which can offer alternative explanations for observed phenomena and potentially resolve long-standing problems in cosmology.
  • Interdisciplinary Collaborations: Exploring the implications of disformal transformations requires expertise from multiple disciplines, including theoretical physics, cosmology, and mathematics. This presents an opportunity for interdisciplinary collaborations and the exchange of ideas between researchers with different backgrounds.

References

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