arXiv subjects

Xian-Hui Ge

Publications and source records attributed to Xian-Hui Ge.

At least 19 recordsLinked to original sources

arXiv2026

Quasinormal Modes Criticality across Black Hole Extremality

We investigate the extremal solution branch to nonextremal branch transition in Einstein-Euler-Heisenberg anti-de Sitter black holes, where the nonlinear electromagnetic parameter $λ$ governs the existence of the extremal branch solution. At fixed pressure and charge, extremal black hole only exist for $λ\leqλ_c$. For $λ>λ_c$, the lowest Hawking temperature keeps nonzero. Near this threshold, the lowest temperature follows a linear critical scaling, $T_{\min}\propto(λ-λ_c)^{α_T}$. We investigate the corresponding dynamical behavior by computing the quasinormal modes of a massless scalar perturbation along the lowest-temperature black hole branch. As the critical threshold is approached, two complex-frequency quasinormal modes branches collide on the imaginary axis and reorganize into distinct purely imaginary branches. Then the imaginary parts of these modes, together with higher overtones, reach zero at the critical threshold, described by $Γ_n\propto(λ-λ_c)^{α_n}$, with $α_n\simeqα_T$. The resulting zero-damped modes become increasingly localized near the event horizon, and their relative damping rates closely follow the overtone spacing predicted by the near-horizon AdS$_2$ spectrum. Our results show that the thermodynamic and dynamical critical behavior remain closely connected even when extremal black hole solutions cease to exist, providing further evidence for the relevance of near-extremal spectral behavior in this distinct critical regime.

hep-th↗

arXiv2026

Non-singular cosmologies matching regular black holes

We construct a new non-singular cosmological model matched to a Minkowski-core regular black hole by means of a modified Oppenheimer--Snyder framework. Its dynamics in both dust-only and scalar-field scenarios is studied and compared with that of two other non-singular models as well as the classical standard cosmology. The results show that, although all three non-singular cosmologies share identical late-time behavior and allow for a natural embedding of inflation in the scalar-field setting, they exhibit qualitatively distinct non-singular features at very early times. For the new cosmology specifically, we also investigate the scenarios of other cosmological fluids and, more generally, of multiple coexisting fluids. This cosmological model is found to manifest an intriguing symmetry between its asymptotic past and future: without a cosmological constant both limits are asymptotically Minkowski, whereas with a positive one both are asymptotically de Sitter. Furthermore, a dynamical stability analysis reveals that the asymptotic-past state of this model is a robust attractor, thereby requiring no extreme fine-tuning of the initial conditions.

gr-qc↗

arXiv2026

A $q$-Inspired Radial Quantum Kinematics

We study how the one-dimensional deformation suggested by nonadditive $q$-calculus can be extended to a rotationally covariant quantum model and what observable consequences follow from this extension. We choose a radial extension about a distinguished center in which only the radial derivative is deformed, while tangential derivatives retain their ordinary form. Within this model, we construct self-adjoint frame-momentum operators and derive a rotationally invariant uncertainty bound with a correction proportional to the mean distance from the center. We then adopt a non-negative kinetic Hamiltonian built from these momenta and derive the leading harmonic-oscillator energy shifts for weak deformation. The energy corrections split the levels with different orbital angular momenta that are degenerate in the undeformed oscillator, while preserving the degeneracy associated with rotational symmetry.

quant-ph↗

arXiv2026

Gravitational-wave signatures of spinning particles around rotating hairy black holes

We study how the spin of a compact secondary and a gravitational-decoupling deformation of the Kerr geometry are imprinted on gravitational waves from strong-field eccentric motion around a rotating black hole. The orbit is evolved with the Mathisson--Papapetrou--Dixon equations under the Tulczyjew spin supplementary condition, and the radiation is computed with the numerical-kludge method. The deformation describes a black hole only below a critical curve in the plane of the two hair parameters. The spin of the secondary pulls the pericenter inward and, above a critical value, carries the particle into the black hole. The hair raises this capture threshold, from $S\simeq0.66$ in Kerr to $0.9$ and above close to the horizon boundary, because it reduces the effective mass near the black hole. The emitted signal remains a discrete comb of orbital harmonics: the spin strengthens the pericenter bursts and shifts power toward higher harmonics, while both the spin and the hair leave their main imprint through an accumulated dephasing. The imprint of the hair is controlled by the parameter that sets the radial reach of the deformation, disappears in the Kerr-like limit of the family, and is amplified by the spin of the secondary. For a source at $2$ Gpc with $M=10^6M_\odot$ and $μ=10M_\odot$, a $6.8$ h segment of the signal carries a signal-to-noise ratio of about $1.4$ in LISA, $2.7$ in Taiji and $0.9$ in TianQin. Within the same segment the more extended deformations become distinguishable from Kerr, first in Taiji; since this holds for a nonspinning secondary, it applies directly to astrophysical EMRIs. The spin-induced frequency shifts are linear in the spin, so the large spins used here are a magnified illustration of a dephasing that, for realistic secondaries, accumulates to a phase of order a radian over an inspiral.

gr-qc↗

arXiv2026

Relative-Entropy Flow Across the Page Transition

We develop a computational framework for the quantum relative entropy based on the replica trick and apply it to analyze the evaporation process method of Jackiw-Teitelboim black holes. We show that the relative entropies between the exact radiation state and the Hawking saddle state and the replica wormholes saddle state quantify information-theoretic costs inherent to coarse-grained semiclassical descriptions. During evaporation, the relative entropy for the Hawking saddle increases monotonically, reflecting a progressively higher thermodynamic cost of sustaining the Hawking description. Conversely, the relative entropy associated with the replica wormholes saddle decreases, which indicates that the description of connected geometries becomes progressively more accurate. Moreover, the sign of the difference between the two quantities reverses precisely at the Page time, providing an information-theoretic diagnosis for the transition between competing gravitational saddles. Our results recast the Page transition as a flow of relative entropy costs between competing semi-classical descriptions, revealing an information-theoretic structure underlying the emergence of effective irreversibility in coarse-grained black hole evaporation.

hep-th↗

arXiv2026

Analytical solution of traversable wormholes in the presence of positive cosmological constant

The construction of traversable wormholes with a cosmological constant, $Λ$, introduces significant challenges and leads to non-trivial modifications of the spacetime geometry. In this work, we obtain an analytical solution describing a locally traversable wormhole for $Λ>0$ following a perturbative approach. Starting from the Ellis-Bronnikov wormhole geometry, we derive the metric deformation induced by the cosmological constant at linear order, assuming $Λr^2_0\ll 1$, where $r_0$ represents the throat of the Ellis-Bronnikov wormhole. We further identify the radial domain of validity of the perturbative solution, which is restricted to $r\ll\sqrt{3/Λ}$. Within this domain, we find that the Ellis-Bronnikov wormhole is modified by the cosmological constant; interestingly, the shape function takes a de Sitter-like form. Nevertheless, we verify that the flare-out condition holds at the deformed throat and find a violation of the null energy condition in its vicinity, as required for traversable WHs. Traversability is further analyzed by evaluating tidal forces and deriving constraints on the velocity required for safe human passage. Additionally, we discuss the possibility of constructing a global extension by matching the perturbative wormhole solution to a Schwarzschild-de Sitter exterior spacetime. Given the recent advances in the observational study of astrophysical compact objects, together with a variety of astrophysical and cosmological observations indicating the existence of a positive cosmological constant, the analytical solution presented here may be of considerable phenomenological interest.

gr-qc↗

arXiv2026

Quantum Mpemba effect in holography

We investigate the quantum Mpemba effect in a holographic superfluid, in which states with stronger initial symmetry breaking relax faster toward the symmetry-restored equilibrium. We demonstrate its emergence by identifying the shifted free energy computed from the energy flux into the black hole horizon as monotonic distance measure. By decomposing the nonlinear bulk dynamics based on quasinormal modes, we reveal that the anomalous relaxation is governed by a dynamical competition in which the slowest-decaying mode is suppressed while the second mode is amplified. These findings provide a holographic perspective on the quantum Mpemba effect in nonequilibrium relaxation involving strongly coupled degrees of freedom.

hep-th↗

arXiv2026

High-Order Pole-Skipping in Near-Extremal Holography

We develop a systematic analytic method for studying high-order pole-skipping in near-extremal holographic black holes. In the near-extremal regime, approaching the limit $T\to0$, the near-horizon geometry develops an approximately $\mathrm{AdS}_2 \times \mathbb{R}^{d-1}$ structure; we show that the mode index $q$ labeling pole-skipping points is identified with the IR conformal dimension $Δ_{\mathrm{IR}} = q$ in the emergent $\mathrm{AdS}_2/\mathrm{CFT}_1$ correspondence, providing a concrete physical interpretation of the subleading pole-skipping tower. The method reorganizes the near-horizon Frobenius expansion according to powers of temperature. This reveals a temperature-graded hierarchical structure that reduces the $n$-th-order pole-skipping condition to a factorized algebraic equation:each pole-skipping momentum depends only on the mode index $q$, not on the order $n$. This $n$-independence produces a high degeneracy as $T\to 0$, where pole-skipping momenta at all orders collapse onto a discrete set of values determined by near-horizon geometry and the scalar field mass; these values can be expressed in terms of thermodynamic quantities such as entropy density and specific heat. In the limit $n \gg 1$ (with $nT$ remaining small), the leading pole-skipping momenta grow asymptotically as $k_{n,n} \propto n$. We compute leading temperature corrections and verify our predictions through numerical analysis of the Dyonic Gubser--Rocha model. The results confirm that high-order pole-skipping at low temperature is governed by near-horizon physics. This provides analytic access to pole-skipping points well beyond those accessible by standard determinant methods and clarifies the structure of holographic Green's functions in the low-temperature regime.

hep-th↗

arXiv2026

Stimulated Emission from Boson Clouds

Gravitational-waves from astrophysical sources are characterized by their extreme faintness, which remains a primary obstacle for both current and next generation detectors. While rotating black holes dressed in superradiant clouds of ultralight bosons are recognized as promising probes of physics beyond the Standard Model, their capacity to actively emit and modulate gravitational radiation remains largely unexamined. Here we demonstrate that these gravitational atoms can function as natural amplifiers of gravitational-waves via a stimulated emission mechanism analogous to astrophysical masers. By formalizing the interaction between the bosonic cloud and an ambient stochastic gravitational-wave background, we establish the rigorous selection rules and threshold conditions that govern this amplification. Our analysis reveals that the emission rate depends critically on the boson mass, potentially yielding an enhancement of several orders of magnitude over spontaneous processes. For representative mass ranges, these amplified signals bridge the sensitivity gap between ground-based interferometers and pulsar timing arrays. These findings suggest that superradiant clouds can effectively boost previously undetectable signals, offering a novel observational frontier for exploring ultralight fields and the Kerr spacetime environment.

gr-qc↗

arXiv2026

Chaotic motion of particles around a Schwarzschild black hole in a swirling electromagnetic background

We investigate the particle motion around a Schwarzschild black hole immersed in a swirling Bertotti-Robinson-Bonnor-Melvin background. This spacetime provides a physically well-motivated framework for studying how the two different electromagnetic components and the swirling deformation affect particle dynamics near compact objects. By employing Poincaré sections, the maximum Lyapunov exponent, the Fast Lyapunov indicator, recurrence analysis and bifurcation diagrams, we show that chaotic motion can already appear in the non-swirling Schwarzschild-Bertotti-Robinson black hole. This indicates that the swirling background is not a necessary condition for chaos in this family of spacetimes, it mainly shifts the parameter region where chaos occurs. We further find that the effects of the two electromagnetic fields are very complicated. In particular, the existence of bound orbits is strongly restricted by the strengths of the two electromagnetic fields and their relative direction. These results provide rich numerical evidence that the chaotic motion of particles is associated with the nonlinear interaction between the accessible phase space, the electromagnetic backreaction and the swirling deformation.

gr-qc↗

arXiv2026

Spin-Hair Induced Chaos of Spinning Test Particles in Rotating Hairy Black Holes

We investigate the finite-time instability of massive spinning test particles around a rotating hairy black hole generated through gravitational decoupling. The particle motion is described by the full Mathisson-Papapetrou-Dixon equations with the Tulczyjew spin supplementary condition, and the sensitivity to initial conditions is measured using a ZAMO-projected finite-time Lyapunov analysis. The hairy deformation is controlled by two parameters: $α$, which sets the deviation from Kerr, and $β$, which changes the radial localization of the deformation. We show that spin-curvature coupling and the hairy geometry can shift the evolved orbit away from the requested seed parameters, making the empirical orbital map essential for interpreting the dynamics. Small-spin and geodesic trajectories remain close to regular behavior, whereas large-spin trajectories show stronger finite-time growth. A scan of the $(S,β)$ plane shows that the instability does not grow monotonically, but appears in localized regions where the particle spin and the radial profile of the hair act cooperatively. Thus, the hairy background does not simply rescale the Kerr result; it reorganizes the strong-field phase-space region sampled by spinning particles.

gr-qc↗

arXiv2026

Emergence of Time Semicrystals in Holographic Driven-Dissipative Systems

Understanding how temporal order degrades in quantum systems remains a central issue in nonequilibrium physics. Here we study the melting of discrete time crystals in a periodically driven holographic system, where a distinct (discrete) time semicrystal phase emerges with persistent temporal order in disorder, bridging discrete time crystals and fully disordered regimes. This phase exhibits a periodic skeleton, with discrete subharmonic peaks persisting atop a continuous spectrum. We extract a critical scaling behavior across the discrete time crystal to time semicrystal transition. Furthermore, even dynamical transitions between distinct periodic skeletons can be clearly identified with systematic log-periodic corrections to power-law scaling, revealing discrete scale invariance. These findings in holography significantly enrich the platforms for studying nonequilibrium phases of matter.

hep-th↗

arXiv2026

Pole-skipping in the de Sitter horizon structure

We study the pole-skipping structure of incoming waves near the cosmic horizon $r=r_c$ in de Sitter (dS) spacetime. We find that the scalar field with spin-0, the Dirac field with spin-1/2, the Maxwell field with spin-1, the Rarita-Schwinger field with spin-3/2, and the gravitational field with spin-2 exhibit the same frequencies $ω_\star$ of pole-skipping points as their corresponding spin fields satisfying the incoming wave conditions in anti-de Sitter (AdS) spacetime. However, the momenta $k_\star$ undergo a shift in complex space, which originates from the spacetime curvature. The shift in momenta at the pole-skipping points could be measured through the operator dimensions $Δ$ in two curved spacetimes, where momenta are mutually complex conjugate in dS and AdS, two opposite curvature spacetimes.

hep-th↗

arXiv2026

Quasi-Normal Modes and Nonlinear Electrodynamics in Black Hole Phase Transitions

We investigate the connection between thermodynamic phase transitions and quasi-normal modes (QNMs) in charged black holes with a positive curvature constant, within the framework of $F(R)$-Euler-Heisenberg gravity. Nonlinear electromagnetic fields lead to rich thermodynamic phase structures and significantly affect the QNMs of massless scalar fields. By analyzing the QNMs spectrum, we find that the transition point marking the disappearance of the divergence in the QNMs slope parameter $K$ aligns with the change of the thermodynamic phase structure described by the heat capacity, within the bounds of computational uncertainty. This precise matching holds under variations of the curvature parameter and charge. Furthermore, we show that larger angular quantum number $l$ diminishes this correspondence, while higher overtone number $n$ restores it beyond a threshold. These findings demonstrate that thermodynamic phase transitions of black holes carry embedded dynamical information, uncovering a fundamental link between black hole thermodynamic and dynamical properties.

hep-th↗

arXiv2025

From Quantum Tsallis Entropy to Strange Metals

We develop a unified framework connecting quantum Tsallis statistics to electronic transport in strongly interacting systems. Starting from Rényi and Tsallis entropies, we construct a quantum Tsallis distribution that reduces to the conventional Fermi--Dirac distribution when $q=1$. For $q$ slightly deviating from unity, the correction term in the occupation function can be mapped to a $q$-deformed Schwarzian action, corresponding to soft reparametrization modes. Coupling these soft modes to electrons via the Fermi Golden Rule yields a modified scattering rate, which reproduces conventional Fermi-liquid behavior at low temperatures and linear-in-temperature resistivity at high temperatures. Using the memory matrix formalism, we analyze magnetotransport, finding a linear-in-field magnetoresistance and a Hall angle consistent with Anderson's two-lifetime scenario. At sufficiently low temperatures, both magnetoresistance and Hall response smoothly recover Fermi-liquid quadratic behaviors. This approach provides a controlled interpolation between Fermi-liquid and non-Fermi-liquid regimes, quantitatively linking $q$-deformation, soft-mode dynamics, and experimentally measurable transport coefficients in strange metals.

cond-mat.str-el↗

arXiv2025

Zeno's paradox and black hole information loss problem

We develop a conceptual parallel between the black hole information problem and Zeno's paradox, highlighting the role of limiting procedures that turn formally infinite constructions into finite physical observables. Building on the replica--wormhole paradigm, we move beyond unitarity restoration to formulate a quantitative notion of irreversibility in Hawking radiation. Our main result is a modular thermodynamic framework for black-hole evaporation, in which modular entropy, entanglement capacity, and relative entropy assume thermodynamic roles. The monotonicity of relative entropy furnishes a generalized second law that determines the arrow of evolution in replica space. We further resolve the apparent tension between the replica method and the quantum no-cloning theorem by interpreting replicas as ensemble representations rather than physical copies of an unknown state, thereby clarifying the operational meaning of gravitational path integrals. A key message of this work is that non-additivity in Tsallis statistics provides an information-theoretic analogue of the correlations induced by replica wormholes.

hep-th↗

arXiv2025

Islands in Kerr-Newman Black Holes

We investigate the information paradox in the four-dimensional Kerr-Newman black hole by employing the recently proposed island paradigm. We first consider the quantum field in the four-dimensional Kerr-Newman spacetime. By employing the near-horizon limit, we demonstrate that the field can be effectively described by a reduced two-dimensional field theory. Consequently, the formula of entanglement entropy in CFT$_2$ can be naturally adapted to this reduced two-dimensional theory. Under the framework of this reduced two-dimensional theory, we show that the entanglement entropy of radiation for the non-extremal case satisfies the unitarity in the later stage of the appearance of the entanglement islands. We further examine the impact of angular momentum and charges on the Page time and the scrambling time. Both quantities increases as the angular momentum increases, while decreases as the charge increases. At last, we consider the near extremal case. Resort to the Kerr/CFT correspondence, the near-horizon geometry of near extremal Kerr-Newman black holes can be taken account for a warped AdS geometry. In this scenario, the low-energy effective degrees of freedom are dominated by the Schwarzian zero mode, resulting in a one-loop correction to the partition function. The entanglement entropy is subsequently recalculated under the thermodynamic with corrections. Through explicit calculations, we finally find that the Page time and the scrambling time exhibits quantum delays. This strongly suggests that the near extremal geometry is governed by the Schwarzian dynamics, in which quantum fluctuations result in a reduced rate of information leakage. Our findings further substantiate the conservation of information and extend the applicability of the island paradigm to the most general stationary spacetime background.

hep-th↗

arXiv2025

Symmetry restoration in a fast scrambling system

Entanglement asymmetry -- used here as a direct probe of symmetry restoration -- provides a sharp diagnostic of post-quench dynamics. We test this idea in the complex Sachdev--Ye--Kitaev model with a conserved U(1) charge. Using exact diagonalization, we track the joint evolution of entanglement entropy and entanglement asymmetry after quenches from charge-asymmetric product states. We find rapid volume-law entanglement growth consistent with the subsystem eigenstate thermalization hypothesis, accompanied by a concurrent decay of entanglement asymmetry to a late-time plateau set by finite-size effects: small subsystems display near-complete restoration, while residual cross-sector weight yields a finite plateau. Notably, we uncover a quantum Mpemba effect: states prepared further from symmetry relax faster and approach lower residual asymmetry; disorder in the couplings renders this behavior more robust and monotonic across parameters. We further derive a Pinsker-type lower bound that ties the decay of asymmetry to differences in subsystem purity, identifying dephasing between U(1) charge sectors as the operative mechanism. These results establish entanglement asymmetry as a sensitive probe of symmetry restoration and thermalization, clarifying finite-size limits in fast-scrambling, closed quantum systems.

cond-mat.str-el↗