# Accreting Schwarzschild-like compact object: Plasma-photon interaction and stability

**Authors:** Avijit Chowdhury, Shauvik Biswas, Sumanta Chakraborty  
**arXiv:** [2405.04006](https://arxiv.org/abs/2405.04006)  
**Date:** 2024-05-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2405.04006v1/

## Key points

- Study focuses on analyzing linear dynamics of electromagnetic fields in plasma around horizon-less exotic compact objects (ECOs)
- Equations reveal presence of quasi-bound states with characteristic oscillations around black hole values for axial and polar modes
- Amplitude and oscillation length of states influenced by non-zero reflectivity and compactness of ECO's surface
- Quasi-bound states exhibit slower decay over time within certain parameter spaces compared to black holes, making ECOs more susceptible to instabilities
- Research provides insights into plasma-photon interactions, stability in exotic compact object environments, superradiance, ergoregion instability quenching, strong-field gravity tests involving plasma, nonlinear photon-plasma interactions near black holes, and fundamental interactions in curved spacetime

## Summary

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The study of accretion around astrophysical compact objects, such as black holes or exotic compact objects (ECOs), is crucial for understanding the dynamics of electromagnetic fields. This paper focuses on analyzing the linear dynamics of these fields in plasma surrounding a static and spherically symmetric horizon-less ECO. The general equations governing electromagnetic wave propagation in this unique background reveal the presence of quasi-bound states with characteristic oscillations around black hole values for both axial and polar modes. Homogeneous and inhomogeneous plasma distributions are considered, highlighting how the amplitude and oscillation length of these states are influenced by the non-zero reflectivity and compactness of the ECO's surface. Interestingly, it is found that these quasi-bound states exhibit slower decay over time within certain parameter spaces compared to black holes, making ECOs more susceptible to instabilities. This emphasizes the importance of understanding plasma-photon interactions and stability in exotic compact object environments. This research also provides valuable insights into related works on superradiance, ergoregion instability quenching, strong-field gravity tests involving plasma, nonlinear photon-plasma interactions near black holes, and fundamental interactions in curved spacetime. These references provide a broader context for exploring new physics and testing theories of gravity in extreme astrophysical scenarios. Overall, this study sheds light on potential instabilities and phenomena unique to accreting plasma around exotic compact objects, contributing to our understanding of their intricate interplay with electromagnetic fields.