Analysis of Kiselev black hole in f(τ, T) gravity through quasinormal modes, greybody factors and thermodynamic quantities

We present an exact static and spherically symmetric black hole configuration in the framework of symmetric teleparallel gravity, where non-metricity is coupled to an axion field. Starting from the modified field equations, we obtain analytical solutions characterized by the mass parameter M and an axion–geometry coupling constant α . The resulting metric exhibits a regular horizon structure with well-behaved curvature invariants. We analyze the thermodynamic quantities including the Hawking temperature, entropy, and heat capacity, and show that the system maintains thermodynamic consistency across the allowed parameter range. As for the analysis of the heat capacity we show that it remains negative for all admissible horizon radii, indicating that the black hole is thermodynamically unstable and does not undergo any phase transition. Furthermore, we study the motion of massive and massless test particles, identifying the conditions for circular orbits and the photon sphere. The axion–non-metricity coupling modifies both the effective potential and the shadow radius, producing observable deviations from the Schwarzschild limit. Using the photon-sphere/eikonal correspondence, the quasinormal mode (QNM) frequencies are computed, revealing that an increase in α enhances both the oscillation frequency and damping rate, ensuring linear stability. Overall, the axion-non-metricity interaction imprints coherent modifications on the black hole s thermodynamics, shadow, and ringdown spectrum, offering potential signatures for testing deviations from general relativity.

Dirac quasinormal modes of charged black holes in f(R, T) gravity with nonlinear electrodynamics

Hydroxylation effects on the DFT-modeled adsorption of benzene and cyclohexane on hematite.

Abstract In this article, we present a theoretical and phenomenological study of the gravastar in the presence of a global monopole in teleparallel gravity, specifically $$f(\mathbb {T})$$ f ( T ) gravity. We have constructed the interior based on both the global monopole and the dark energy, and on the shell, we have taken the stiff matter equation of state. We studied the thin shell surrounding the gravastar using the Israel junction conditions and derived a sufficient condition for its stability. We determined the deflection angle around the gravastar using both Gauss-Bonnet topological methods and analytical Hamilton–Jacobi methods. We checked the shadow around the gravastar at the equator using the ray-tracing method. We have presented the null-geodesic equation as an initial-value problem and applied numerical methods to trace the rays around the gravastar, also illustrating the photon sphere that surrounds it. We further present the complete 3D shadow, incorporating observer inclination and relativistic effects to provide a direct link to high-resolution interferometric imaging. In addition, we have determined the scalar field perturbation in the interior and computed its quasinormal modes using the third-order WKB approximation. The potential is plotted against the tortoise coordinate and shows a single peak with an asymptotic decay, as expected for a stable configuration. Our stability analysis, evidenced by imaginary negative quasinormal modes for various values of $$\eta $$ η , predicts detectable ring-down overtones for the LISA and the Einstein Telescope, thereby establishing a direct phenomenological link between our model and upcoming gravitational-wave observations.

In this Letter, we provide a novel test of general relativity based on ringdown analysis. The test is performed on agnostic models, where the postmerger signal is fitted with a superposition of damped sinusoids. If at least two modes are detected, one has to compute the ratio of the frequencies and of the damping times and compare them against the predictions of general relativity. By considering ratios, the dependency on the black hole's mass is scaled away. Most notably, we find that the ratios vary very little with the spin, the real part depends mostly on the angular momentum of the mode ℓ and the imaginary part depends mostly on the overtone number n: different combinations create specific mode islands. We provide a qualitative explanation of these islands through a semianalytical argument. We discuss the application of the method to future detectors. Finally, we show that ratios in alternative theories of gravity or between different field content drastically differ from those of general relativity.

A new exact static and spherically symmetric black hole solution embedded in a cored Plummer dark matter halo is constructed. The impact of the cored Plummer dark matter halo on photon dynamics and its stablity, black hole shadow, eikonal limit quasinormal modes and black hole thermodynamics-phase transition are investigated. Light rings, gravitational lensing and shadow formation are studied based on the null geodesics which is derived via the principle of least action. The stability of circular photon orbits is characterized by the Lyapunov exponent, which is shown to control the imaginary part of massless quasinormal mode frequencies. The thermodynamic properties of the black hole-dark matter system are examined through the mass function, the analog black hole’s enthalpy, entropy, temperature, heat capacity and Gibbs free energy, from which the black hole phase transition is investigated. We analytically and graphically show how the cored Plummer dark matter halo modifies the black hole’s optical and thermodynamic behavior, enhancing null geodesic and thermodynamic stability also allowing phase transitions absent in pure Schwarzschild solution.

We explore the weak-field phenomenology of a compact star spacetime modified by quantum gravitational corrections derived from the effective field theoretical (EFT) approach by Calmet et al. [1]. These corrections, encoded in non-local curvature-squared terms, distinguish matter-supported geometries from vacuum solutions by contributing nontrivial modifications at order O ( G 2 ). Using the corrected metric, we analytically derive expressions for the deflection of light and time-like particles via the Gauss-Bonnet theorem. We further compute the perihelion advance of Mercury, Shapiro time delay, and gravitational redshift within this framework. Each classical observable acquires quantum corrections that, though exceedingly small (on the order of 10 − 9 arcsecond per century for perihelion precession and 10 − 18 arcsecond for light deflection) represent potential imprints of quantum gravity. The Shapiro delay and redshift likewise exhibit finite, source-dependent deviations from their general relativistic predictions due to the modified temporal metric component. While current observational capabilities remain insufficient to detect these minute effects, the analysis demonstrates that quantum gravitational signatures are embedded even in weak-field observables. Last, we study massless scalar perturbations in static, spherically symmetric spacetimes by analyzing their quasinormal modes (QNMs) and greybody factors using the WKB method and Pade resummation. Our findings demonstrate that increasing the coupling parameter enhances spacetime stability and significantly influences emission spectra through frequency-dependent transparency. Moreover, the results underscore that quantum-corrected star metrics yield phenomenological distinctions from classical black holes, particularly near the Planck scale, where vacuum solutions lose validity.

Screened graphene channels support a single longitudinal collective mode whose response can be fixed by exact AdS/CFT correlators. Using the exact neutral BTZ Dirichlet correlator together with a calibrated mixed-boundary prescription for a dynamical boundary electromagnetic field, we derive the leading collective plasmon response in a screened single-mode channel. The AdS/CFT Dirichlet sector determines a universal thermal pole structure and a real light-cone fundamental mode, while the mixed-boundary completion generates a controlled complex shift of the physical excitation. This implies a plasmon linewidth that scales as the square root of temperature and wave vector and obeys a simple leading relation between reactive shift and damping. The result provides a controlled holographic baseline for confined graphene plasmons and a starting point for finite-density, disorder, phonon, and parity-odd extensions.

Quasi-normal modes of a multi-dimensional rotating Kerr black hole

We present a fully Bayesian, data-driven framework for identifying quasinormal modes in high-accuracy Cauchy characteristic evolution gravitational waveforms. Applying this to a public catalog, we identify quasinormal mode overtones, retrograde modes, and nonlinear modes up to cubic order in the ringdown. Multiple high-order overtones are found near the merger, confirming their physical significance for modeling the ringdown. The ringdown mode content is tabulated across a wide range of start times for all available simulations, providing a systematic reference for theoretical and observational studies. We also search for late-time power-law tails, which are, as expected, absent from the Cauchy characteristic evolution waveforms.

In a recent work [Opt. Express32(5), 7171 (2024)10.1364/OE.515087], an efficient method based on the coupling theory of quasinormal mode (QNM) was proposed for the electromagnetic modeling of large-scale arrays of optical nanoresonators. In this method, the problem of QNM far-field divergence in the QNM-coupling theory is solved by introducing regularized QNM (RQNM). However, this method requires that each scatterer of resonator in the array is located in a homogeneous background medium, so that the RQNM far field over a large spatial range can be computed efficiently through the plane-wave expansion calculated by the stationary-phase principle (PESP). In this paper, we extend the method to the case where each resonator in the array is located on a metallic substrate. We propose to use radially propagating surface plasmon (RSP) to achieve an efficient calculation of the RQNM far field over a large spatial range near the metallic substrate surface for every single resonator. Thus, based on the QNM-coupling theory, an efficient computation of the electromagnetic response of a large-scale array of optical nanoresonators on a metallic substrate can be achieved. The numerical example of a large-scale periodic array of nanoantennas on a gold substrate with a dielectric spacer shows that compared to traditional full-wave numerical methods, this method can reduce the computation time by 1∼2 orders of magnitude while maintaining a moderate computational accuracy, and enable the calculation of the electromagnetic response of arrays with an overall size exceeding 50 × 50 wavelengths. Benefiting from the high computational efficiency and physical intuitiveness of this method, we elucidate the impact of array size, period, and field coupling range (far beyond the tight-binding approximation) on the optical response. This method provides an efficient and intuitive tool for the analysis and design of devices based on optical nanoresonator arrays on a metallic substrate.

We investigate the quasinormal modes (QNMs) of a massive scalar field in the background of a regular black hole arising from the proper-time flow in asymptotically safe gravity. This quantum-corrected geometry, characterized by a deformation parameter q , smoothly interpolates between a near-extremal regular black hole and the Schwarzschild solution. Employing both the WKB approximation with Padé resummation and time-domain integration, we compute the complex frequencies for various values of the scalar field mass μ, multipole number ℓ, and deformation parameter q. We observe that the real parts of the QNMs increase with the field mass, while the imaginary parts exhibit behavior indicative of long-lived modes. Although quasi-resonances are not detected in the time-domain profiles due to the dominance of late-time tails, we find that the asymptotic decay follows an oscillatory slowly decaying behavior with the power-law envelope.

Thermodynamics, shadow, and quasinormal modes of AdS Ayón–Beato–García massive black hole

Shadow ringing of black holes from photon sphere quasinormal modes

This Letter deals with the gravitational angular momentum carried by axial (odd-parity) perturbations of the Bardeen regular black hole within the teleparallel equivalent of general relativity (TEGR). Using the Hamiltonian definition of conserved quantities in TEGR, we derive a closed expression for the perturbative angular momentum δ J in terms of the axial perturbation function . The result exhibits a sharp multipolar selection rule: δ J vanishes for odd values of the multipole index ℓ, while even-ℓ modes yield a nonzero contribution. The radial and temporal behavior of δ J is illustrated using the known axial quasinormal modes of the Bardeen spacetime.

We study quasinormal modes of scalar, electromagnetic, and Dirac perturbations of four-dimensional regular black holes arising in non-polynomial quasi-topological gravity. Starting from a more general class of metric functions constructed within the same framework, from which two representative cases are selected for detailed analysis, we examine their spectral properties. While the fundamental mode changes smoothly with the regularization parameter, higher overtones display a markedly enhanced sensitivity to near-horizon modifications, leading to the characteristic outburst of overtones. Remarkably, pushing the WKB approximation to sufficiently high orders with Padé resummation already allows one to detect the onset of this effect. Time-domain analysis and the Leaver method confirm that the relative error of the higher-order WKB approach is much smaller than the observed effect. Our results indicate that overtone dynamics provides a sensitive probe of geometrically regular black holes and that high-order WKB methods remain capable of capturing nontrivial spectral features beyond the fundamental mode.

Abstract In this work, we study how the spin of particle modes influences particle creation, greybody factors, absorption, and evaporation of a black hole within the framework of modified electrodynamics in f ( R , T ) gravity, recently proposed in Róis et al. (Phys Rev D 111(12):124044, 2025). All spin sectors-scalar, vector, tensor, and spinorial-are analyzed to obtain the corresponding features. For particle creation, we consider massless bosonic and fermionic perturbations to determine the respective particle densities. Analytical expressions for the greybody factors are derived, with suitable approximations for the tensor and spinorial cases. The absorption cross section is computed numerically, and using the Stefan–Boltzmann law, we estimate the black hole evaporation lifetime. The associated energy and particle emission rates are also discussed, along with the correspondence between quasinormal modes and greybody factors.

Finite curvature construction of regular black holes and quasinormal mode analysis

Continued fraction method for high overtone quasinormal modes in effective potentials with a discontinuity