arXiv subjects

Yan-Gang Miao

Publications and source records attributed to Yan-Gang Miao.

At least 19 recordsLinked to original sources

arXiv2026

Darboux Isospectrality Constraints on Quasinormal Modes Deformed by Bumps

A localized Gaussian or Pöschl-Teller bump is widely used to probe the sensitivity of Schwarzschild quasinormal modes, where it is typically added to both the Regge-Wheeler and Zerilli potentials. We show that such an additive prescription is generically incompatible with the Darboux transformation connecting the two parity sectors. The reason is that such a transformation restricts a parity-blind bump to a fixed family of bumps with an unavoidable $r^{-2}$ tail, excluding any Gaussian or Pöschl-Teller profile with arbitrary amplitude, center, or width in the additive prescription. We give the complete classification of Darboux-admissible axial and polar pairs of bumps and propose two consistent scenarios: Darboux generator prescription in which a Gaussian or Pöschl-Teller profile is retained as a generator of the bump pair rather than as the bump itself, and Riccati completion prescription in which a Gaussian or Pöschl-Teller profile is regarded as one of the bump pair and its partner will be solved from the Riccati equation. Our frequency-domain calculations confirm that a finite and spurious axial-polar splitting of quasinormal modes will be produced if the Darboux-consistent scenarios are absent, while the centroid shift of the fundamental mode is nearly unchanged.

gr-qc↗

arXiv2026

No-Go Theorem for Singularity Resolution

We prove a No-Go theorem for singularity resolution in homogeneous, spatially flat gravitational collapse: within this sector, quantum corrections introduced solely as non-vanishing effective matter sources are insufficient to halt singularities in any vacuum-normalized analytic gravitational theory, including general relativity and other theories with analytic gravitational actions. This theorem rules out singularity resolution via effective energy density in a broad class of quantum gravity approaches, including asymptotic safety and noncommutative geometry theories, where the effective energy densities yield finite-time singularities or geodesic incompleteness. The singularity resolution strictly requires non-analytic modifications of the gravitational response at $\mathbb{Q}=0$, or a vanishing effective energy density at high densities (as realized in loop quantum gravity's Planck stars). The theorem is proved via an intrinsic $f(\mathbb{Q})$ gravity framework, extended universally to general relativity, $f(\mathbb{R})$, and $f(\mathbb{T})$ theories through the geometrical trinity at the level of the corresponding homogeneous collapse response structure--with regularity criteria and junction conditions grounded in non-metricity, free of standard GR tools.

gr-qc↗

arXiv2026

A pre-merger-informed spectral-level ringdown inference framework for black-hole spectroscopy

Black-hole spectroscopy aims to infer properties of the remnant spacetime from the quasinormal-mode (QNM) spectrum of the gravitational-wave ringdown signal. In most implementations, however, this inference is performed with waveform models that already incorporate Kerr or other theory-specific QNM spectral relations, thereby entangling spectral measurement with remnant or beyond-Kerr parameter inference. At the same time, conventional ringdown analyses commonly excise the pre-merger data, which in principle contain information about the excitation amplitudes and phases of the QNMs. We introduce \texttt{SPRING} (\textit{Spectral-level Pre-merger-informed RINGdown inference}), a framework designed to separate ringdown spectral inference from theory-side interpretation while propagating pre-merger information through amplitude-scale estimation. As a demonstration, we apply \texttt{SPRING} to GW250114 using an agnostic two-component damped-sinusoid (2DS) model for Kerr remnant inference. \texttt{SPRING} improves the Bayesian support for the agnostic 2DS signal model relative to analyses that do not use pre-merger information, with an increase of $Δ\ln B\sim 5$--$10$. The resulting remnant posterior remains closely consistent with the inspiral-merger-ringdown estimate, despite the extra freedom introduced by the second DS component. This work bridges pre-merger information and ringdown inference, establishing a fully spectral-level route for future black-hole spectroscopy.

gr-qc↗

arXiv2026

The impact of plunging matter on black-hole waveform

In this work, we introduce a novel framework to investigate ringdown gravitational waveforms in the presence of dynamical matter fields outside the horizon of a black hole. We systematically analyze two distinct scenarios of dynamical matter fields: motion along geodesics and uniform motion with constant velocity. Our results reveal rich phenomenology in the ringdown gravitational wave signals, including the suppression or enhancement of echoes, frequency shifts in the decay oscillations, and intricate modulations of the power-law tails. Notably, we demonstrate that subluminal moving potentials can produce irregular echo patterns and shift the dominant frequencies, offering potential new observational signatures beyond the already-known ringdown analyses. This study provides a new perspective for probing dynamic environments around black holes and offers a theoretical foundation for interpreting possible deviations in future gravitational wave detections.

gr-qc↗

arXiv2025

Quasinormal modes of regular black holes surrounded by skewed dark matter distributions

Regular black holes, nonsingular solutions to gravitational collapse with quantum corrections, offer a compelling alternative to classical black holes with curvature singularities. In this work, we investigate how the presence of skewed dark matter distributions outside the innermost stable circular orbit of regular black holes modifies the gravitational wave signals emitted by such objects. Rather than introducing corrections directly into an effective potential, we model the influence of dark matter through metric corrections, allowing a full control over the spatial distribution and abundance of dark matter. We demonstrate that a skewed normal profile generically introduces shallow potential wells or secondary barriers in the effective potential of perturbation equations, depending sensitively on the type of perturbations: scalar, spinor, or tensor. These modifications lead to distinctive quasinormal mode features, including long-lived modes, echo effects, and in some cases, altered stability behaviors. Notably, the axial and polar sectors of tensor field perturbations respond asymmetrically to identical dark matter profiles, revealing a deeper structural distinction in their perturbation dynamics. These results provide a theoretical framework for probing regular black holes in the dark matter environment through gravitational wave observations.

gr-qc↗

arXiv2025

Perturbations of Einstein--Maxwell--phantom spacetime: Instabilities of charged Ellis--Bronnikov wormholes and quasinormal modes of black holes

Phantom scalar fields, as a viable candidate for dark energy, have been instrumental in eliminating spacetime singularities and constructing wormholes and regular black holes. We investigate the Einstein-Maxwell-phantom (EMP) framework, in which the Ellis-Bronnikov wormholes can be charged and regular black holes can be admitted. While the previous study has shown the stability of EMP wormholes under massless scalar field perturbations, we further perform a comprehensive linear analysis of the EMP spacetime through gravito-electromagnetic field perturbations in the axial sector and phantom scalar field perturbations under an approximate treatment in the polar sector. Our analyses of effective potentials and finite difference time profiles reveal the linear instability of EMP wormholes. In the black hole scenario, the quasinormal spectra of Type I black holes, where the matrix-valued direct integration method and the Prony method are used, recover those of general relativity (GR) when the scalar charge goes to zero. Finally, by introducing the concepts of generalized specific charge and mixing angle, we quantify how the relative contributions between the phantom scalar and the electromagnetic fields modify the quasinormal spectra, and we assess the prospects for detecting spectral deviations between the EMP theory and GR in gravitational wave observation.

gr-qc↗

arXiv2025

A theory-agnostic hierarchical Bayesian framework for black-hole spectroscopy: a case study on GW250114 in Einstein-dilaton-Gauss-Bonnet gravity

Black-hole spectroscopy has emerged as a powerful probe of strong-field gravity in the era of gravitational-wave astronomy. In this context, many current tests of modified or extended gravity are implemented by searching for predicted signatures modeled as perturbative corrections to general-relativistic waveforms; however, this approach may introduce model-dependent systematics and limit applicability to broader classes of theories. To complement such methods, we develop a theory-agnostic hierarchical Bayesian framework that connects ringdown observations -- modeled as damped sinusoids -- directly with theoretical quasinormal mode spectra, performing the comparison at the spectral level rather than through theory-specific waveform matching. The framework incorporates a soft-truncation module to account for the finite domain of validity in the theory's parameter space and is equipped with quantitative diagnostics that identify stable analysis time windows. As an illustrative application, we implement the framework within Einstein-dilaton-Gauss-Bonnet gravity and apply it to the gravitational-wave event GW250114, finding that the resulting posterior for the dimensionless coupling $ζ$ is robust against prior assumptions yet remains only weakly informative over the range considered in this work. We further perform controlled ringdown injection studies across different values of $ζ$, confirming that nonzero couplings can be recovered while also indicating a potential systematic effect: Kerr-based priors in the $ζ$ inference may partially absorb spectral deviations arising in alternative theories of gravity. This work establishes a transparent and extensible foundation for future strong-field gravity tests, naturally compatible with the growing precision and modal resolution of next-generation gravitational-wave detectors.

gr-qc↗

arXiv2025

Comparison of Quasinormal Modes of Black Holes in $f(\mathbb{T})$ and $f(\mathbb{Q})$ Gravity

We investigate the quasinormal modes of static and spherically symmetric black holes in vacuum within the framework of $f(\mathbb{Q}) = \mathbb{Q} + α\mathbb{Q}^2$ gravity, and compare them with those in $f(\mathbb{T}) = \mathbb{T} + α\mathbb{T}^2$ gravity. Based on the Symmetric Teleparallel Equivalent of General Relativity, we notice that the gravitational effects arise from non-metricity (the covariant derivative of metrics) in $f(\mathbb{Q})$ gravity rather than curvature in $f(R)$ or torsion in $f(\mathbb{T})$. Using the finite difference method and the sixth-order WKB method, we compute the quasinormal modes of massless scalar field and electromagnetic field perturbations. Tables of quasinormal frequencies for various parameter configurations are provided based on the sixth-order WKB method. Our findings reveal the differences in the quasinormal modes of black holes in $f(\mathbb{Q})$ gravity compared to those in $f(R)$ and $f(\mathbb{T})$ gravity. This variation demonstrates the impact of different parameter values, offering insights into the characteristics of $f(\mathbb{Q})$ gravity. These results provide the theoretical groundwork for assessing alternative gravities' viability through gravitational wave data, and aid probably in picking out the alternative gravity theory that best aligns with the empirical reality.

gr-qc↗

arXiv2025

Axisymmetric generalization of zero-scalar-curvature solutions from the Schwarzschild metric via the Newman-Janis algorithm

We address a specific issue of the Newman-Janis algorithm: How to determine the general form of the complex transformation for the Schwarzschild metric and ensure that the resulting axisymmetric metric satisfies the zero-scalar-curvature condition, $R=0$. In this context, the zero-scalar-curvature condition acts as a constraint. Owing to this condition, we refer to the class of black holes as the ``Newman-Janis class of Schwarzschild black holes" in order to emphasize Newman-Janis algorithm's potential as a classification tool for axisymmetric black holes. The general complex transformation we derive not only generates the Kerr, Taub-NUT, and Kerr-Taub-NUT black holes under specific choices of parameters but also suggests the existence of additional axisymmetric black holes. Our findings open an alternative avenue using the Newman-Janis algorithm for the construction of new axisymmetric black holes.

gr-qc↗

arXiv2025

Comment on "Black holes in $f(\mathbb{Q})$ gravity"

In the work [Phys.Rev.D 105 (2022) 2, 024042], D'Ambrosio et al. investigated spherically symmetric black hole solutions in $f(\mathbb{Q})$ gravity, where several solutions satisfy the condition: $g_{tt}g_{rr} = \mathrm{const}$. This condition is characteristic of many black holes, including the Schwarzschild spacetime. In this Comment, we argue that no nontrivial vacuum black hole solutions satisfy this condition in $f(\mathbb{Q})$ gravity. We demonstrate our claim by reexamining the field equations under the "Set 2" connection called by D'Ambrosio et al., which is necessary for obtaining solutions distinct from those of general relativity (GR). For the case where the free parameters $c$ and $k$ are zero, i.e., Option 2 in their work, we show that any attempt to find a solution beyond GR forces the non-metricity scalar to vanish ($\mathbb{Q}=0$), which trivializes the field equations and does not describe a valid black hole solution. Our findings indicate that the condition, $g_{tt}g_{rr} = \mathrm{const.}$, is overly restrictive for finding new, static and spherically symmetric vacuum black holes in $f(\mathbb{Q})$ gravity. This conclusion does not depend on the specific form of $f(\mathbb{Q})$. We also briefly discuss Option 1 that was not addressed in D'Ambrosio et al.'s work, and give new constraints for the selection of parameters $c$ and $k$.

gr-qc↗

arXiv2025

Echoes and quasi-normal modes of perturbations around Schwarzchild traversable wormholes

We investigate the waveforms and quasi-normal modes around Schwarzschild traversable wormholes under different field perturbations, including the scalar field, the electromagnetic (vector) field, and the axial gravitational (tensor) field perturbations. Our results indicate that under the influence of the matter at the throat of the wormhole, a Dirac $δ$-function distribution of matter appears in the effective potentials of the scalar and axial gravitational perturbations and it affects the propagation of these two types of perturbations in spacetime. However, the matter at the throat has no influence on the propagation of electromagnetic perturbations. Furthermore, we quantify the impact of throat matter on both the perturbation waveforms and quasi-normal modes for all three field types. Through comparative studies between Schwarzschild traversable wormholes and Schwarzschild black holes, we identify two distinct features. Firstly, the perturbation waveforms exhibit echoes and damping oscillations around wormholes, whereas they solely display damping oscillations around black holes. Secondly, the difference between the adjacent peaks varies with the mass parameter and the throat radial coordinate in the waveform around Schwarzschild traversable wormholes, while a constant peak spacing occurs, which is determined solely by mass, in the waveform around Schwarzschild black holes. Based on these findings, we propose a framework to estimate the mass parameter and throat radial coordinate of Schwarzschild traversable wormholes through waveforms and quasi-normal modes. Our analyses provide a more profound comprehension of the inherent characteristics of Schwarzschild traversable wormholes.

gr-qc↗

arXiv2024

Phase diagrams of quasinormal frequencies for Schwarzschild, Kerr, and Taub-NUT black holes

The Newman-Janis algorithm, which involves complex-coordinate transformations, establishes connections between static and spherically symmetric black holes and rotating and/or axially symmetric ones, such as between Schwarzschild black holes and Kerr black holes, and between Schwarzschild black holes and Taub-NUT black holes. However, the transformations in the two samples are based on different physical mechanisms. The former connection arises from the exponentiation of spin operators, while the latter from a duality operation. In this paper, we mainly investigate how the connections manifest in the dynamics of black holes. Specifically, we focus on studying the correlations of quasinormal frequencies among Schwarzschild, Kerr, and Taub-NUT black holes. This analysis allows us to explore the physics of complex-coordinate transformations in the spectrum of quasinormal frequencies.

gr-qc↗

arXiv2024

Scalar fields around a rotating loop quantum gravity black hole: Waveform, quasi-normal modes and superradiance

The rotating loop quantum gravity black hole is a newly proposed non-singular black hole, which eliminates spacetime singularities when a regularization parameter is introduced through loop quantum corrections. This parameter is expected to give rise to observable effects. In this paper, the dynamical behavior of a scalar field near a rotating loop quantum gravity black hole is investigated. Given a small initial perturbation, we obtain the waveform of massless scalar fields evolving over time. By analyzing the waveform, we find that the regularization parameter only affects the damping oscillation of waveform, but not the initial outburst and late-time tail stages. This behavior is characterized by quasi-normal modes. Under scalar field perturbations, the loop quantum black holes remain stable. Moreover, we calculate the quasi-normal modes of massive scalar fields by three numerical methods, which are the Prony, WKB, and shooting methods, respectively. Our results indicate that the real part of quasi-normal modes depends only on the regularization parameter, while the imaginary part does not only on the regularization parameter but also on the angular momentum. Finally, we study the amplification effect of rotating black holes, i.e., the superradiance. Our analyses indicate the existence of stronger superradiance around loop quantum gravity black holes compared to Kerr ones.

gr-qc↗

arXiv2024

Signal of phase transition hidden in quasinormal modes of regular AdS black holes

We discuss the intrinsic relations between thermodynamic phase transitions and quasinormal modes in regular AdS black holes, specifically in the Bardeen and Hayward AdS classes. To this end, we calculate the quasinormal modes of massless scalar field perturbations around small and large black holes via the Horowitz-Hubeny method. By investigating the isobaric and isothermal phase transitions for Bardeen and Hayward AdS black holes in detail, we observe that a dramatic change of quasinormal modes appears near the phase transition point of small and large black holes, and that it corresponds to the swallow tail structure in the plane of Gibbs free energy with respect to pressure. Moreover, by analyzing the evolution of black holes along the coexistence curve of small and large black hole phases, we also observe the dramatic change in quasinormal modes. Such a phenomenon confirms the signal of the phase transition in the quasinormal mode spectrum, which can be understood as a thermodynamic signal hidden in the dynamical spectrum.

gr-qc↗

arXiv2024

Preliminary analyses on dynamics and thermodynamics of rotating regular black holes

We investigate the dynamic and thermodynamic laws governing rotating regular black holes. By analyzing dynamic properties, i.e., the interaction between scalar particles and rotating regular black holes, we establish the criteria that determine whether such black holes satisfy the laws of thermodynamics or not. In addition, we provide the general form of conserved quantities related to rotating regular black holes, including the relevant flows associated with neutral scalar particles. Meanwhile, we reexamine the relationship between the third law of thermodynamics and weak cosmic censorship conjecture for rotating regular black holes. In accordance with the criteria mentioned above, we discuss the laws of thermodynamics for three models of rotating regular black holes: Rotating Hayward black holes, Kerr black-bounce solutions, and loop quantum gravity black holes. Our findings indicate that none of the three models satisfies the first law of thermodynamics. In particular, the first and third models fail to comply with the three laws of thermodynamics, while the second model satisfies only the second and third laws of thermodynamics. Finally, we attempt to rescue the laws of thermodynamics by modifying entropy or extending phase space. However, the two scenarios are not able to ensure the three laws of thermodynamics in the three models, which reveals an unusual property of rotating regular black holes.

gr-qc↗

arXiv2024

Recovery of consistency in thermodynamics of regular black holes in Einstein's gravity coupled with nonlinear electrodynamics

As one of candidate theories in the construction of regular black holes, Einstein's gravity coupled with nonlinear electrodynamics has been a topic of great concerns. Owing to the coupling between Einstein's gravity and nonlinear electromagnetic fields, we need to reconsider the first law of thermodynamics, which will lead to a new thermodynamic phase space. In such a phase space, the equation of state accurately describes the complete phase transition process of regular black holes. The Maxwell equal area law strictly holds when the phase transition occurs, and the entropy obeys the Bekenstein-Hawking area formula, which is compatible with the situation in Einstein's gravity.

gr-qc↗

arXiv2023

A regular black hole as the final state of evolution of a singular black hole

We propose a novel black hole model in which singular and regular black holes are combined as a whole and more precisely singular and regular black holes are regarded as different states of parameter evolution. We refer to them as singular and regular states, respectively. Furthermore, the regular state is depicted by the final state of parameter evolution in the model. We also present the sources that can generate such a black hole spacetime in the framework of $F(R)$ gravity. This theory of modified gravity is adopted because it offers a possible resolution to a tough issue in the thermodynamics of regular black holes, namely the discrepancy between the thermal entropy and Wald entropy. The dynamics and thermodynamics of the novel black hole model are also discussed when a singular state evolves into a regular state during the change of charge or horizon radius from its initial value to its extreme value.

gr-qc↗

arXiv2023

Regular black holes: A short topic review

The essential singularity in Einstein's gravity can be avoidable if the preconditions of Penrose's theorem can be bypassed, i.e., if the strong energy condition is broken in the vicinity of a black hole center. The singularity mentioned here includes two aspects: (i) the divergence of curvature invariants, and (ii) the incompleteness of geodesics. Both aspects are now taken into account in order to determine whether a black hole contains essential singularities. In this sense, black holes without essential singularities are dubbed regular (non-singular) black holes. The regular black holes have some intriguing phenomena that are different from those of singular black holes, and such phenomena have inspired numerous studies. In this review, we summarize the current topics that are associated with regular black holes.

gr-qc↗