arXiv subjects

Yu-Qi Lei

Publications and source records attributed to Yu-Qi Lei.

9 recordsLinked to original sources

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

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 Poincar\'{e} 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

Astrophysically Realistic Secondary Spins Trigger Chaos in Schwarzschild Spacetime and Discernible Gravitational Wave Signatures

Chaos in extreme-mass-ratio inspirals is often thought to require unrealistically large secondary spins, making its astrophysical relevance uncertain. However, we find that chaos persists across the astrophysically realistic spin range for a spinning secondary orbiting a Schwarzschild black hole. This nonintegrable dynamics leaves clear signatures in the emitted gravitational waves. Nearby regular and chaotic trajectories can remain similar in the time domain and retain broadly aligned dominant spectral peaks, yet chaotic signals develop a much less discrete frequency-domain structure with dense inter-peak power. Furthermore, we introduce a local spectral-flatness measure and find it to be several hundred times larger for the chaotic signal than for the neighboring regular signals. Finally, a change in the secondary spin by as little as $1\%$ of its maximal physically allowed value can drive the system from regular to chaotic motion and produce distinctive detector-level waveforms.

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↗

arXiv2025

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↗

arXiv2024

Thermodynamic Stability Versus Chaos Bound Violation in D-dimensional RN Black Holes: Angular Momentum Effects and Phase Transitions

We compute the Lyapunov exponents for test particles orbiting in unstable circular trajectories around D-dimensional Reissner-Nordström (RN) black holes, scrutinizing instances of the chaos bound violation. Notably, we discover that an increase in particle angular momentum exacerbates the breach of the chaos bound. Our research centrally investigates the correlation between black hole thermodynamic phase transitions and the breaking of the chaos limit. Findings suggest that the chaos bound can only be transgressed within thermodynamically stable phases of black holes. Specifically, in the four-dimensional scenario, the critical point of the thermodynamic phase transition aligns with the threshold condition that delineates the onset of chaos bound violation. These outcomes underscore a deep-rooted link between the thermodynamic stability of black holes and the constraints imposed by the chaos bound on particle dynamics.

hep-th↗

arXiv2023

Stationary equilibrium of test particles near charged black branes with the hyperscaling violating factor

We explore the upper bound of the Lyapunov exponent for test particles that maintain equilibrium in the radial direction near the charged black brane with the hyperscaling violating factor. The influences of black brane parameters (hyperscaling violation exponent $θ$ and dynamical exponent $z$) are investigated. We show that the equilibrium in the radial direction of test particles can violate the chaos bound. The chaos bound is more easily violated for the near-extremal charged black branes. When the null energy condition ($T_{μν}ξ^μξ^ν\geq 0$) is broken, the bound is also more likely to be violated. These results indicate that the chaos bound of particle motion is related to the temperature of the black hole and the null energy condition (NEC). By considering the zero-temperature and $T_{μν}ξ^μξ^ν=0$ cases, we obtain the critical parameters $θ_c$ and $z_c$ for the violation of chaos bound. The chaos bound is always satisfied in the range $θ> θ_c$ or $z>z_c$.

hep-th↗

arXiv2022

Circular Motion of Charged Particles near Charged Black Hole

We study the circular motion of charged particles near a charged black hole. The general form of the Lyapunov exponent of charged particles is obtained by using the Jacobian matrix. The results show that the chaos bound can be saturated by the circular motion of charged particles on the horizon. By further expanding the Lyapunov exponent near the horizon and investigating Reissner-Nordström(RN) black holes with different $M/Q$, we find that in contrast to the static equilibrium, the circular motion of charged particles can have a larger Lyapunov exponent due to the existence of angular momentum. For the RN black holes which have the mass-charge ratio $1<M/Q <1.1547$, the chaos bound is locally violated by the null and the time-like circular motion with large angular momentum. As an illustration of the universality of our results, we study the charged particles' circular motion near the Reissner-Nordström Anti-de Sitter (RN-AdS) black hole and find that the null and the time-like circular motion with large angular momentum can exceed the chaos bound under the background of RN-AdS black holes with the mass-charge ratio in the range $1.23132<M/Q<1.75225$.

hep-th↗

arXiv2021

Chaos of Particle Motion near the Black Hole with Quasi-topological Electromagnetism

We explore the chaotic behavior of particle motion in a black hole with quasi-topological electromagnetism. The chaos bound is found to be violated in the higher order expansion of the metric function and the electric potential near the horizon. We draw the Poincare sections of particle motion corresponding to the chaos bound violated and non-violated cases, respectively. Then we study the relationship between the maximal Lyapunov exponent λ_s defined by the static equilibrium and the Lyapunov exponent of the particle geodesic motion near the Reissner-Nordstrom(RN) black hole and the black hole with quasi-topological electromagnetism. We find an interesting relationship between the Lyapunov exponent λ_{ph} of photon's radial falling into the black hole and the maximal Lyapunov exponent λ_s. For the black holes whose metric function increases monotonically with radius outside horizon, this leads to λ_{ph} \geq 2λ_s.

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