Fractal temporal dynamics in black hole accretion and quasi-periodic oscillation scaling

Yildiz L., Kayki D., Güdekli E.

EUROPEAN PHYSICAL JOURNAL C, cilt.85, sa.12, 2025 (SCI-Expanded, Scopus)

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 85 Sayı: 12
  • Basım Tarihi: 2025
  • Doi Numarası: 10.1140/epjc/s10052-025-15228-0
  • Dergi Adı: EUROPEAN PHYSICAL JOURNAL C
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC, zbMATH, Directory of Open Access Journals, Nature Index
  • İstanbul Üniversitesi Adresli: Evet

Özet

Accretion processes around black holes play central role in high-energy astrophysics by governing compact object growth and driving luminous emissions across the electromagnetic spectrum. In this work, we propose a theoretical framework in which the local flow of time near the event horizon acquires a fractal structure, potentially arising from quantum gravitational fluctuations at Planckian length scales. This fractal temporal behavior, characterized by a scaling relation tf = talpha with 0 < alpha < 1, modifies the time evolution of surface density in viscous accretion disks. We derive a generalized diffusion equation incorporating the fractaltime exponent alpha and perform numerical simulations across a wide range of black-hole masses (5 M(R) to 109 M(R)) and accretion rates (0.01-1.0 Mcenter dotEdd). Our results reveal enhanced modulation in the accretion luminosity and the emergence of quasi-periodic oscillations (QPOs) in the X-ray light curves. The predicted QPO frequencies, which range from 4-8 Hz for stellar-mass black holes, scale with the fractal exponent and follow nu QPO oc M-alpha BH (classical limit alpha = 1), remaining within the detection capabilities of current instruments such as NICER, XMM-Newton, and NuSTAR. These findings indicate that microscopic spacetime fluctuations may leave macroscopic imprints on accretion dynamics, thereby providing an observational probe of fractal-time behavior near black holes. This work offers a testable connection between quantum gravitational microphysics and observable X-ray variability.