arXiv subjects

Zongyuan Qin

Publications and source records attributed to Zongyuan Qin.

3 recordsLinked to original sources

arXiv2026

Radiative properties and optical appearance of a thin accretion disk around a charged-PFDM black hole

Accretion onto magnetically charged black holes in a perfect fluid dark matter (PFDM) background opens a new window for testing strong-field gravity. This paper investigates the radiative properties and optical appearance of a thin accretion disk surrounding a charged-PFDM black hole. We numerically compute the radiative energy flux, temperature distribution, and radiative efficiency, and employ a ray-tracing method to construct the direct images, secondary images, redshift distribution, and observed flux. By comparing with the Schwarzschild and pure PFDM cases, we find that the thin-disk efficiency of the charged-PFDM black hole lies between the two, with the magnetic charge partially counteracting the dark-matter-induced efficiency enhancement; for M87*, the efficiency is estimated to be 7\%--8\%. The optical appearance is predominantly governed by the PFDM parameter, while the magnetic charge plays only a marginal role. Larger inclination angles give rise to stronger Doppler asymmetry, producing the characteristic ``hat-like'' shape. These results provide falsifiable predictions for future high-resolution observations, such as those by ngEHT, to distinguish dark-matter environments from magnetic-charge effects.

astro-ph.HE↗

arXiv2026

Quasinormal Modes, Partial Transmission Probabilities, and Hod's Conjecture of Charged Black Holes in Perfect Fluid Dark Matter within Kalb-Ramond Gravity

Within the Kalb-Ramond field-induced Lorentz-violating gravity, we investigate the perturbation dynamics and quasinormal mode (QNM) spectra of a charged black hole immersed in perfect fluid dark matter. The background spacetime is characterized by the Lorentz-violating parameter tau, the electric charge Q/M, and the dark matter parameter lambda/M. Owing to the non-zero vacuum expectation value of the KR field, the metric function approaches 1/(1-tau) at infinity instead of 1, rendering the spacetime non-asymptotically flat. Under the test-field approximation, the equations of motion for three types of perturbations (scalar, electromagnetic, and axial gravitational) are reduced to Schrodinger-type radial equations with single-peak effective potentials. The QNM frequencies are cross-validated using the sixth-order WKB method and the time-domain Prony method, while the partial transmission probabilities are computed within the WKB scattering framework. Parameter scans show that tau exerts the strongest influence on the QNM spectrum, followed by lambda/M, with Q/M having the weakest effect; the same ordering holds for the partial transmission probabilities. Under the same parameters, the QNM frequencies of the three perturbations follow the order scalar > electromagnetic > gravitational, whereas the transmission probabilities exhibit the reverse order, reflecting the different impact of the effective potential height on the oscillation frequency and on the transmission probability. The Hod conjecture |Im(omega)| <= pi T_H holds throughout the parameter range examined.

gr-qc↗

arXiv2026

Detecting Black hole surrounded by perfect fluid dark matter in Kalb-Ramond fields using quasinormal modes

This paper investigates the characteristics of quasinormal modes (QNMs) of static, spherically symmetric black holes under the combined influence of spontaneous Lorentz symmetry breaking (LSB) induced by the Kalb-Ramond (KR) field and perfect fluid dark matter (PFDM). Using M87$^\ast$ shadow data from the Event Horizon Telescope (EHT), we constrain the LSB factor $τ$ and PFDM parameter $ζ$ at 1$σ$ confidence. By combining the sixth-order WKB approximation method with timedomain numerical integration, we systematically compute the complex frequency spectrum of QNMs for black holes in this spacetime background. The numerical results reveal an intriguing conclusion: as the LSB factor $τ$ or the PFDM parameter $ζ$ increases, both the real part and the absolute value of the imaginary part of the QNMs frequencies exhibit a monotonic increase, demonstrating a unique "stiffening" effect. This characteristic stands in stark contrast to the decreasing trend of QNMs frequencies observed in models that consider only traditional dark matter, revealing the critical influence of the coupling between the KR field and PFDM on the dynamic evolution of black holes. This study not only enriches and deepens the understanding of black hole perturbation theory within the framework of modified gravity but also, by identifying the distinctive spectral features of QNMs, offers the potential to distinguish whether the KR field and dark matter are coupled in future observations. Thus, it provides a theoretical foundation for testing mechanisms of spacetime symmetry breaking beyond the standard model and for exploring the nature of dark matter.

gr-qc↗