2025/07/28 by Wang, Mingzhi, Zhang, Cheng-Yong, Chen, Songbai +1 · 3 citations
#FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2507.20569
We investigate the dynamic shadows of a black hole with a self-interacting massive complex scalar hair. The complex scalar field ψevolves with time t, and its magnitude on the apparent horizon |ψh| starts from zero, undergoes a sharp rise followed by rapid oscillations, and eventually converges to a constant value. The variation in the photon sphere radius rps is similar to that of the magnitude |ψh|. Owing to the emergence of the complex scalar hair ψ, the apparent horizon radius rh starts increasing sharply and then smoothly approaches a stable value eventually. The shadow radius Rsh of the black hole with an accretion disk increases with time to at the observer's position. In the absence of an accretion disk, the shadow radius Rsh is larger and also increases as to increases. Furthermore, we slice the dynamical spacetime into spacelike hypersurfaces for all time points t. For the case with an accretion disk, the variation in Rsh is similar to that in the apparent horizon rh, because the inner edge of the accretion disk extends to the apparent horizon. In the absence of an accretion disk, the variation in Rsh is similar to that in the photon sphere radius rps, because the black hole shadow boundary is determined by the photon sphere. As the variation in rps is induced by ψ, it can be stated that the variation in the size of the shadow is similarly caused by the change in ψ. Regardless of the presence or absence of the accretion disk, the emergence of the complex scalar hair ψcauses the radius Rsh of the shadow to start changing. Moreover, we investigate the time delay Δt of lights propagating from light sources to the observer. These findings not only enrich the theoretical models of dynamic black hole shadows but also provide a foundation for testing black hole spacetime dynamics.