Accretion flow around Kerr metric in the infra-red limit of asymptotically safe gravity

TL;DR

This paper explores how quantum corrections in asymptotically safe gravity influence accretion disk dynamics and QPOs around Kerr black holes, revealing modifications in shock cone structure and oscillation modes.

Contribution

It introduces a detailed analysis of accretion flows in quantum-corrected Kerr metrics, highlighting the impact of quantum parameters on shock structures and oscillation modes.

Findings

Quantum corrections widen shock cones and weaken post-shock compression.

QPO frequencies are consistent across different radial locations.

Moderate quantum corrections produce harmonic ratios like 2:1 and 3:2.

Abstract

We investigate accretion disk dynamics and the formation of quasi-periodic oscillations (QPOs) in the infrared limit around Kerr-like black holes in asymptotically safe gravity. Relativistic hydrodynamic solutions of Bondi-Hoyle-Lyttleton (BHL) accretion reveal that quantum corrections significantly modify the structure of the shock cone formed around the black hole. The black hole spin controls the azimuthal asymmetry of the shock cone through frame-dragging effects, whereas the quantum correction parameter effectively reduces the strength of gravitational focusing by modifying the metric coefficients in the strong-field region, resulting in a wider shock opening angle, weaker post-shock compression, and reduced density concentration within the cone. Time-dependent mass accretion rates reveal oscillation modes trapped within the shock cone. The power spectral density (PSD) investigations suggest that these modes naturally generate low-frequency QPOs, whose amplitudes, coherence, and harmonic structure depend on both the spin and the quantum correction parameter. The PSD analyses performed at different radial locations reveal that identical QPO frequencies are obtained in all cases. The numerically detected frequencies result from the excitation of global oscillation modes trapped within the post-shock region. The resulting global modes are found to consist of fundamental frequencies, their associated harmonic overtones, and near-commensurate frequency ratios such as 2:1 and 3:2. Coherent oscillations are enhanced and near-commensurate frequency ratios are produced when moderate rotation and moderate quantum corrections are coupled. Large quantum correction parameters, on the other hand, wash out unique spectral peaks and suppress oscillation amplitudes.