Shadow signatures and near-horizon energy accumulation in coherent quantum sine-integral black holes

Quantum modifications of black hole spacetimes can lead to observable departures from the predictions of classical general relativity, particularly in the strong-gravity regime near the event horizon. In this context, the coherent quantum black hole model introduces a sine-integral correction to the gravitational potential, characterized by a coherence scale (R_s), which softens the central singularity and alters the near-horizon geometry. Motivated by the growing precision of black hole imaging and strong-field observations, we explore how these quantum-induced effects influence photon motion and the resulting shadow structure. Considering representative values within the interval (R_s \in [0.5M, 1.2M]), we show that the photon sphere shifts inward while the critical impact parameter decreases, reaching values such as (b_{\rm crit}\approx 4.764M) for (R_s=0.5M). Consequently, the shadow radius becomes systematically smaller and develops a more intricate structure than in the Schwarzschild case ((b_{\rm crit}=3\sqrt{3}M \approx 5.196M)). The analysis of the corresponding intensity distributions also reveals a pronounced enhancement of radiation near the shadow boundary, especially for intermediate coherence scales. This feature can be attributed to photons remaining longer within the modified near-horizon region before escaping toward distant observers. Such an increase in brightness may therefore provide a possible observational signature of quantum corrections at horizon scales. Furthermore, although the geometry allows radiation and energy to accumulate around an effective horizon surface, its response to perturbations differs from that expected for compact objects with stable light rings. Instead of contracting under backreaction effects, the accumulation surface shifts outward.

Source: arXiv:2610.08841v1 - http://arxiv.org/abs/2610.08841v1 PDF: https://arxiv.org/pdf/2610.08841v1 Original Link: http://arxiv.org/abs/2610.08841v1