We study properties of the Maxwell electromagnetic invariant in the external
region of spinning and charged horizonless stars. We analytically find that the
minimum negative value of the Maxwell electromagnetic invariant is obtained on
the equator of the star surface. We are interested in scalar fields
non-minimally coupled to the Maxwell electromagnetic invariant. The negative
enough Maxwell electromagnetic invariant can lead to a negative effective mass
term, which forms a binding potential well for the scalar field. It means that
the scalar field coupled to the Maxwell electromagnetic invariant may mostly
exist around the surface of the star on the equator.

Future Roadmap: Challenges and Opportunities on the Horizon

Based on the findings of the study on the properties of the Maxwell electromagnetic invariant in the external region of spinning and charged horizonless stars, several potential challenges and opportunities can be identified for future exploration. These conclusions open up avenues for further research in understanding the behavior of scalar fields non-minimally coupled to the Maxwell electromagnetic invariant.

1. Further Investigation of the Equator of Star Surface

The analytical discovery that the minimum negative value of the Maxwell electromagnetic invariant is obtained on the equator of the star surface warrants further investigation. Researchers can delve deeper into understanding the physical processes and implications associated with this phenomenon. Detailed studies could focus on uncovering the reasons behind this behavior and exploring its implications in different astrophysical contexts.

2. Understanding the Binding Potential Well

The finding that a negative enough Maxwell electromagnetic invariant can lead to a negative effective mass term and create a binding potential well for the scalar field presents an interesting opportunity for exploration. Further investigation could elucidate the characteristics of this binding potential well and its impact on the behavior of scalar fields. Researchers could examine how this phenomenon differs from standard potential wells and its relevance in explaining certain astrophysical phenomena.

3. Expanding to Other Star Types

The study focused on horizonless stars, but similar investigations can be extended to different types of stars. Researchers could explore the behavior of the Maxwell electromagnetic invariant and its coupling with scalar fields in various star configurations, including spinning, charged, or even stars with horizons. This expansion could provide a broader understanding of how these factors influence the electromagnetic properties and potential well formations.

4. Applications in Astrophysics

The presence of scalar fields coupled to the Maxwell electromagnetic invariant mostly around the surface of the star on the equator suggests potential applications in astrophysics. Researchers could explore how these findings can be utilized to explain or predict specific astrophysical phenomena. The understanding of the electromagnetic properties in this context could have implications for gravitational wave generation, stellar dynamics, or even the formation and evolution of galaxies.

5. Exploring Non-Minimal Couplings

The study primarily focused on scalar fields non-minimally coupled to the Maxwell electromagnetic invariant. Future research could expand on this by studying other types of non-minimal couplings and their impact on the behavior of scalar fields. By investigating a range of coupling scenarios, researchers could gain insights into the range of possibilities and potential effects that non-minimal couplings have on the electromagnetic properties.

Conclusion

The analytical findings regarding the Maxwell electromagnetic invariant in the external region of spinning and charged horizonless stars open up several exciting avenues for future exploration. By further investigating the equator of star surfaces, understanding binding potential wells, expanding to different star configurations, identifying astrophysical applications, and exploring various non-minimal couplings, researchers can deepen their understanding of the electromagnetic properties in these contexts. These avenues hold promising potential for unraveling new insights into astrophysics and advancing our knowledge of fundamental physical phenomena.

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