arXiv subjects

De-Cheng Zou

Publications and source records attributed to De-Cheng Zou.

At least 19 recordsLinked to original sources

arXiv2026

Absorption and scattering of massless scalar waves by black holes with scalar hair

We use partial waves to study massless scalar absorption and scattering by the normal ($ξ=5$) and phantom ($ξ=-2$) Bakopoulos--Nakas black holes, described by mass $M$ and scalar charge $q$. At fixed mass $M=1$, increasing $q/M$ decreases the horizon area and geometric capture cross section in the normal branch, but it increases both in the phantom branch. The low-frequency absorption tends to the horizon area, while photon-sphere scaling brings the absorption spectra close together. In scattering picture, charge and branch change the interference pattern, and higher frequencies make the fringes narrow. However, matching the capture or glory scale of the normal branch with Reissner--Nordström black holes indicates finite-frequency differences.

gr-qc↗

arXiv2026

Quasinormal modes of Type I perturbations of dilaton-Euler-Heisenberg black holes

We study the type I quasinormal modes (QNMs) of magnetically charged dilaton--Euler--Heisenberg (dEH) black holes, where axial gravitational and polar electromagnetic perturbations are coupled. Direct integration and Chebyshev pseudospectral methods give consistent QNM frequencies for the fundamental branches continued from Schwarzschild at $\ell=1,2,3$. Varying $α$ at fixed $ζ=α-β$ changes the spectrum on the same background. The damping response depends on charge and multipole and can have opposite signs for the two coupled branches. For $ζ<0$, dipole damping decreases with charge toward horizon merger. For $ζ>0$, the Type I charge range extends beyond the complementary polarization's local angular-gradient bound. All tracked modes remain damped in the nonextremal ranges, supporting the stability of these branches.

gr-qc↗

arXiv2026

Axial gravitational quasinormal modes of magnetically charged black holes

In this paper, we consider axial perturbations on the magnetically charged string-inspired Euler-Heisenberg black hole. Since axial metric perturbation decouples from axial electromagnetic perturbation, here we mainly focus on axial gravitational perturbation. By using WKB approximation and AIM methods, we make a detailed analysis of the gravitational quasinormal frequencies by varying the characteristic parameters of gravitational perturbation and black holes. It is found these results obtained through the AIM method are in good agreement with those of obtained by WKB method, including these results extracted from the time-domain profiles. The greybody factor is calculated by WKB method. The effects of these parameters $Q_m$, $ε$ and multipole number $l$ on the greybody factor are also studied.

gr-qc↗

arXiv2026

Phase transitions and quasinormal modes of Euler-Heisenberg-dilaton AdS black holes

In this paper, we study phase transitions and scalar quasinormal modes(QNMs) of magnetically charged Euler--Heisenberg-dilaton AdS black holes in the extended phase space. We classify the horizon structures for all three signs of the EH coupling and derive the extended first law when the pressure and coupling are varied. For negative coupling, the physical branch exhibits a Van der Waals-like small/large black-hole transition. Using the improved asymptotic iteration method, we find two separated QNM trajectories below the critical pressure, whereas they merge into one continuous curve at the critical point. The GHS limit and the positive couplings considered here do not produce a finite-radius critical point.

hep-th↗

arXiv2026

Time-domain analysis of scalar perturbations of Kerr--Newman black holes with Chern--Simons and Maxwell couplings

To study the onset of scalarization, we investigate linear scalar perturbations around Kerr--Newman black holes in the Einstein-Chern-Simons-Maxwell-scalar theory with quadratic Chern--Simons (CS) coupling $γ$ ($\hatγ=γ/M^2$) and Maxwell coupling $η$. For this purpose, we employ hyperboloidal Rácz--Tóth evolution and a stationary axisymmetric zero-mode computation. The resulting thresholds are compared with the time-domain response at representative points. For $\hatγ=0$, we find two asymmetric threshold branches in $η$, while for $\hatγ=η$, the two branches have opposite signs and unequal magnitudes. For unequal CS and Maxwell couplings, the two real threshold branches merge as the spin or CS coupling increases.

gr-qc↗

arXiv2026

Nonlinear scalarization and thermodynamics in Einstein-Phantom scalar-Gauss-Bonnet theory

We study nonlinear scalarization of Schwarzschild black-holes for a phantom scalar coupled to the Gauss--Bonnet invariant. Three polynomial couplings satisfying $ζ''(0)=0$ are introduced to investigate its nonlinear coupling dependence. Since the phantom factor $ε$ disappears in the probe scalar equation, its nonlinear evolution is the same as in the canonical scalar theory. We construct nodeless probe solutions and fully backreacted two branches of lower and primary. At equal mass and equal temperature, respectively, the lower branches have higher Wald entropy and lower Helmholtz free energy than primary branch, but their heat capacities are negative. This implies that lower branch favors than primary branch. Finally, we show that there is no nonlinerly stable scalar phase for a phantom kinetic theory.

gr-qc↗

arXiv2026

Quasinormal modes of type II-perturbation for dilaton-Euler-Heisenberg black holes

We study the quasinormal modes (QNMs) of Type II perturbations for dilaton-Euler-Heisenberg (dEH) black holes. These perturbations consist of coupled even-parity gravitational and dilaton perturbations together with odd-parity electromagnetic perturbations. The background is described by mass $M$, magnetic charge $Q_m$, and dilaton coupling difference $ζ=α-β$ to the Euler-Heisenberg term. To find the QNM frequencies, we need to find the parameter space of $(ζ, Q_m/M)$ that is free from vector ghosts. For the $\ell=1$ mode, the radiative block couples the dilaton and axial electromagnetic amplitudes, whereas the $\ell=2$ mode also contains metric amplitudes, so the frequencies are obtained from matrix-valued boundary-value problems. We calculate QNM frequencies for the fundamental ($n=0$) branch with direct integration and the Chebyshev pseudospectral method, and compare the two computations wherever their charge intervals overlap. We find that the $\ell=1,2$ modes in the $n=0$ branch remain damped over the ghost-free parameter domain, supporting the stability of dEH black holes against Type II perturbations. The Type I sector will be presented elsewhere; no claim is made here about that sector, higher multipoles, or overtones.

gr-qc↗

arXiv2026

Charge-dependent scalarization of Einstein- Euler-Heisenberg black holes

Charge-dependent scalarization of the Einstein-Euler-Heisenberg (EEH) black hole is carried out in the EEH-scalar theory by introducing an exponential scalar coupling with coupling constant $α$ to the Maxwell and nonlinear electrodynamic terms. The bald black hole (EEHBH) is described by mass $M$ and arbitrary magnetic charge $q$ and has a single horizon when choosing the action parameter $μ=0.3$. Here, we find the critical onset charge $q_c=r_+^2/\sqrt{2μ}$ with $r_+(M,q_c)$ the outer horizon radius from the resonance condition. The spontaneous scalarization ($α^+$) of this black hole is available for charge $0 q_c$ and negative $α$. The former case of $q=0.5$ implies infinite branches of scalarized EEHBHs but its fundamental branch ($n=0$) is stable against the $l=0$ modes considered here, while for $q=2$ and $q=20$, one stable scalarized branch is found for each charge within the explored parameter ranges.

gr-qc↗

arXiv2026

Critical Scalarization for a Self-Gravitating Bosonic Condensate

We establish a minimal nonrelativistic realization of scalarization in a self-gravitating bosonic condensate coupled to a scalar response field. A local effective-mass shift and nonlinear saturation generate a multibranch structure with two distinct transition routes. In the linearly stable regime, a finite perturbation drives a first-order transition with type-I logarithmic scaling near threshold. Beyond the linear onset, small perturbations grow tachyonically, and the response time controls both the growth and the subsequent breathing dynamics. These results identify a common mechanism for scalarization across relativistic compact objects and nonrelativistic condensates, and point toward laboratory analogues in coherent media.

gr-qc↗

arXiv2026

Spontaneous scalarization of regular Hayward black holes in Einstein-nonlinear electromagnetic-scalar gravity

Regular Hayward black holes provide a useful setting for investigating scalarization in theories with nonminimally coupled matter sectors. Within the framework of Einstein-nonlinear electromagnetic-scalar gravity, we identify the tachyonic threshold that signals the bifurcation from the bald Hayward background and then obtain scalarized charged black holes for both quadratic $(1-αϕ^2)$ and exponential $(e^{-αϕ^2})$ couplings. These configurations form a discrete set of branches classified by the number of nodes in the scalar field. The branch with $n=0$ is the fundamental branch, whereas solutions with $n\geq 1$ are excited branches. By studying radial perturbations, we find that the fundamental branch is stable for both coupling choices, which makes it the most relevant branch for future phenomenological and observational studies.

gr-qc↗

arXiv2026

Quasinormal frequencies and greybody factors for axial perturbations of dilaton-Euler-Heisenberg de Sitter black holes

We investigate the quasinormal modes (QNMs) and greybody factors of dilaton-Euler-Heisenberg (dEH) de Sitter (dS) black holes in string-inspired Euler-Heisenberg gravity. Since the axial gravitational and electromagnetic perturbations decouple, we treat them independently. By applying the asymptotic iteration method (AIM) alongside a sixth-order WKB approximation, we compute the quasinormal frequencies and find excellent agreement between the two approaches. We also find that the QNM spectra depend sensitively on the magnetic charge $Q_{\text{m}}$, cosmological constant $Λ$, and nonlinear coupling $ε$, with a notable topological anomaly appearing in the electromagnetic frequency trajectories. Additionally, larger values of $Q_{\text{m}}$ or the multipole number $l$ generally suppress wave transmission, while the electromagnetic sector with $ε=1$ exhibits an anomalous response.

hep-th↗

arXiv2026

Curvature-induced scalarization of charged AdS black holes

We investigate how a negative cosmological constant affects the Gauss-Bonnet (GB) scalarization in the Einstein-Maxwell-scalar-Gauss-Bonnet theory with a scalar coupling constant $η$ to GB term. We focus on the instability of Reissner-Nordström-AdS (RN-AdS) black holes under a scalar perturbation governed by an effective mass $μ^2_{\text{eff}}$ sourced by the GB term. Unlike the asymptotically flat spacetime case, the onset of scalarization is not merely determined by $μ^2_{\text{eff}} < 0$, but it is constrained by the Breitenlohner-Freedman (BF) bound. In case that the BF bound is violated ($η>2.25$ with $Λ=-0.5$), one may find AdS-tachyonic instability. We find that for $0<η<2.25$, the GB$^+$ scalarization may be performed through spontaneous scalarization, while for $η<0$ the GB$^-$ scalarization is found to give the single branch of scalarized AdS black holes. For the GB$^+$ scalarization in $η_{th}\leη<2.25$ with $η_{th}$ threshold instability, we obtain the single branch ($n=0$ fundamental branch) of scalarized AdS black holes, in contrast to the infinite branches in asymptotically flat spacetime. A bulk fixed-charge thermodynamic analysis is performed thoroughly for GB$^\pm$ scalarizations.

gr-qc↗

arXiv2026

Polar perturbations of dilaton-Euler-Heisenberg black holes

We investigate the quasinormal modes of polar metric-dilaton perturbations around the dilaton-Euler-Heisenberg (dEH) black holes with dilaton hair. The dEH black holes are obtained from the Einstein-Maxwell-dilaton theory with two dilaton coupling parameters ($α,β$) to the nonlinear Euler-Heisenberg term. We compute the quasinormal mode spectra by making use of two numerical techniques: direct integration and matrix values continued fraction methods. An excellent agreement is found between two approaches, confirming the robustness of our computation. We present the fundamental quasinormal frequencies for both gravitational and dilaton modes and analyze their dependence on the magnetic charge ($Q_m$), angular momentum quantum number ($l$), and coupling parameter ($ε=α-β$). All negative imaginary quasinormal frequencies for polar metric-dilaton perturbations imply that the dEH black hole with dilaton hair is stable against dilaton with $l=0,1,2,3$ and gravitational modes with $l=2,3$. Also, our results reveal distinct qualitative behaviors between $ε=1$ and $ε=-1$, particularly in the damping rates near the extremality.

gr-qc↗

arXiv2026

Quasinormal modes of massless scalar and electromagnetic perturbations for Euler-Heisenberg black holes surrounded by perfect fluid dark matter

We investigate the quasinormal modes of massless scalar and electromagnetic perturbations in charged Euler--Heisenberg black holes surrounded by perfect fluid dark matter. The quasinormal frequencies are calculated using the asymptotic iteration method and the sixth-order WKB approximation, and the relative deviation between the two methods is quantitatively analyzed to verify the reliability of results. The greybody factors for both perturbations are also evaluated within the sixth-order WKB framework. We systematically examine the effects of the black hole charge $Q$, nonlinear electrodynamic parameter $a$, dark matter parameter $λ$, and angular quantum number $l$ on the quasinormal frequencies and greybody factors. We find that these parameters significantly modify the structure of the effective potential barriers, and thus affect the oscillation frequencies, damping rates, and wave transmission and reflection properties of the perturbed fields.

gr-qc↗

arXiv2026

Spin-Induced Nonlinear Scalarization of Kerr Black Holes in Einstein-scalar-Gauss-Bonnet Gravity

We investigate spin-induced scalarization of Kerr black holes in an Einstein-scalar-Gauss-Bonnet (EsGB) model that does not admit a linear tachyonic instability of the scalar-free solution. The scalarization mechanism is therefore genuinely nonlinear. We first analyze the decoupled scalar dynamics on fixed Kerr backgrounds and show that sufficiently rapid rotation modifies the Gauss-Bonnet invariant such that a negative near-horizon region develops near the poles. This region provides a geometric trapping mechanism for nonlinear scalar growth, which becomes effective above a threshold spin $χ=0.5$. We then construct stationary scalarized black hole solutions with full backreaction and determine their domain of existence. We find that the solutions occupy a finite low-mass high-spin wedge in the spin-mass plane. This is in contrast to spin-induced spontaneous scalarization, where the scalarized solutions form a narrow band. In this wedge, toward the high-spin end, the scalar hair becomes stronger, and the solutions approach a near-extremal regime, while toward the low-spin boundary, the scalar field is strongly suppressed and approaches a weak-hair limit as $χ\to 0.5$.

gr-qc↗

arXiv2026

Thermodynamics and phase transitions of nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory

We investigate the thermodynamic properties of static nonlinearly scalarized black holes in Einstein-scalar-Gauss-Bonnet theory with polynomial coupling functions. Based on the scalarized solutions constructed previously, we compute thermodynamical quantities of these scalarized black holes. Moreover, we examine the first law of black hole thermodynamics and consider the phase transitions between Schwarzschild and scalarized black holes. It shows that a phase transition from Schwarzschild black hole to scalarized black hole is a first-order with non-zero latent heat.

gr-qc↗

arXiv2026

Spin-charge induced scalarization of Kerr-Newman black holes in the Einstein-Maxwell-scalar theory with scalar potential

We investigate the spin-charge-induced scalarization of Kerr--Newman (KN) black holes in the Einstein--Maxwell-scalar (EMS) theory with a scalar potential and positive coupling parameter. In the linearized theory, there exists a bound of $0<a<a_0$ with onset spin $a_c$ for the negative region signaling instability by analyzing the effective scalar mass term in the $θ$-direction. Solving the $(2+1)$-dimensional evolution equation numerically, we find the region where the KN black hole becomes unstable, giving rise to scalarized KN black holes. The threshold curve for representing the boundary between stable and unstable KN black holes depends on charge $Q$, scalar mass $m_ϕ$, coupling parameter $α$, and spin parameter $a$ with upper bound $a^2\le M^2-Q^2$.

gr-qc↗

arXiv2026

Phase Structure of Scalarized Black Holes in Einstein-Scalar-Gauss-Bonnet Gravity

We revisit scalarized black holes in Einstein-scalar-Gauss-Bonnet gravity and analyze the thermodynamic phase transition between the Schwarzschild solution of general relativity and scalarized black holes. Restricting to spherically symmetric configurations, we investigate several classes of scalar-Gauss-Bonnet coupling functions. For the simplest quadratic coupling that triggers spontaneous scalarization, the scalarized solutions are thermodynamically disfavored and no phase transition occurs. For an exponential coupling, the phase structure depends strongly on the coupling parameter, allowing for the absence of a transition, a continuous second-order transition, or a discontinuous first-order transition. For couplings leading to purely nonlinear scalarization, we find either a first-order transition or no transition. These results reveal a rich phase structure of scalarized black holes controlled by the scalar-Gauss-Bonnet coupling.

gr-qc↗