Black holes surrounded by PFDM in Kalb-Ramond gravity: from thermodynamics to QPO tests
Аннотация
Abstract Studying black holes in alternative gravitational frameworks is crucial for understanding the interplay between dark matter and modified gravity. This work examines black holes immersed in perfect fluid dark matter (PFDM) within the Kalb–Ramond (KR) gravity framework. The KR field, a rank-2 antisymmetric tensor, introduces additional degrees of freedom that alter spacetime geometry and affect particle dynamics. We derive the metric for a black hole embedded in PFDM and analyze the circular motion of test particles. By investigating the effective potential, energy, and angular momentum, we determine conditions for stable circular orbits and explore the impact of KR field parameters and PFDM properties. Beyond kinematics, we study quasi-periodic oscillations (QPOs) commonly observed in the X-ray spectra of black hole accretion disks. We link QPO frequencies to orbital properties in our model, proposing an observational test to distinguish KR gravity with PFDM from general relativity. Additionally, we explore the thermodynamic aspects of these black holes, calculating temperature, entropy, and heat capacity to assess the impact of the KR field and PFDM on stability and phase transitions. Radiation properties are also investigated, including modifications to radiation due to the influence of the PFDM and the KR field on the event horizon. Our results reveal that KR gravity and PFDM generate distinctive signatures in particle dynamics, QPO patterns, thermodynamics, and radiation, offering potential observational tests to differentiate these models from standard general relativity (GR).