Shadows of rotating wormholes (1803.11422v2)

Abstract: We study shadows cast by a certain class of rotating wormholes and point out the crucial role of a rotating wormhole throat in the formation of a shadow. Overlooking this crucial role of a wormhole throat has resulted incomplete results in the previous studies on shadows of the same class of rotating wormholes. We explore the dependence of the shadows on the spin of the wormholes. We compare our results with that of the Kerr black hole. With increasing values of the spin, the shapes of the wormhole shadows start deviating considerably from that of the black hole. Such considerable deviation, if detected in future observations, may possibly indicate the presence of a wormhole. In other words, the results obtained here indicate that, through the observations of their shadows, the wormholes which are considered in this work and have reasonable spin, can be distinguished from a black hole.

• The paper establishes that the wormhole throat plays a critical role in shaping shadows through circular photon orbits.
• It demonstrates through analytical and numerical methods that increasing spin in wormholes leads to pronounced deviations from Kerr black hole shadows.
• The study highlights the significance of critical impact parameters in defining shadow boundaries, offering potential for observational diagnostics.

Overview of "Shadows of Rotating Wormholes"

The paper "Shadows of Rotating Wormholes" explores the study of shadows cast by a specific class of rotating wormholes—those belonging to the Teo class—and emphasizes the crucial role played by the rotating wormhole throat in shadow formation. The author identifies that previous studies have overlooked this aspect, leading to incomplete conclusions regarding the shadows of rotating wormholes. By reevaluating the problem and employing a more comprehensive approach, the paper strives to accurately depict shadow shapes, demonstrating how these can be differentiated from those of the Kerr black hole.

Key Findings and Numerical Results

• Wormhole Throat's Role: The paper successfully establishes that the wormhole throat, due to its geometrical properties, significantly contributes to the formation of shadows in rotating wormholes. The involvement of the throat results in the appearance of circular photon orbits, which prior studies on such wormholes failed to acknowledge.
• Deviations from Kerr Black Hole Shadows: Through analytical and numerical techniques, it's observed in the study that the shadows of rotating wormholes diverge notably from the well-studied Kerr black hole shadows, especially as the wormhole's spin increases. While both shadows appear nearly circular at a low spin, the deviation becomes pronounced with higher spins, presenting potential opportunities for distinguishing wormholes from black holes in observations.
• Impact Parameters and Photon Orbits: The paper discusses the way critical impact parameters define the boundaries of shadows and illustrates how certain unstable circular photon orbits are responsible for the shadow formation.

Implications and Future Directions

This research holds significant theoretical implications as it challenges earlier assumptions and encourages more nuanced investigations into wormhole shadows. It also opens up opportunities for advancing observational techniques that can probe for distinctions between rotating wormholes and rotating black holes. Practically, it suggests that variations in shadow contours may serve as a diagnostic tool in identifying possible wormhole candidates among astronomical observations.

In terms of future research directions, one viable pathway is the exploration of broader classes of rotating wormholes beyond the Teo class to validate whether the conclusions from this study apply universally across different wormhole models. Moreover, integrating modified gravity theories might offer further insights into wormhole geometries and shadow formations.

In conclusion, the paper provides critical insights into wormhole physics by elucidating the role of wormhole throats in shadow formation and enhancing the understanding of phenomenological differences between wormholes and black holes. The findings challenge previous conclusions and lay the groundwork for future exploration both theoretically and observationally within the field of gravitational astrophysics.