arXiv subjects

Jun-Kun Zhao

Publications and source records attributed to Jun-Kun Zhao.

7 recordsLinked to original sources

arXiv2026

Transgression Completion for Chern-Simons Black Hole Thermodynamics

The quantum statistical relation, which identifies the thermodynamic free energy with the on-shell Euclidean action, is a cornerstone of black hole thermodynamics. In this Letter, we demonstrate that it fails for charged magnetic black holes in five-dimensional Einstein-Maxwell-Chern-Simons theory unless the action is formulated in a gauge-invariant manner. In particular, the free energy computed via the quantum statistical relation violates both the first law of thermodynamics and hydrodynamics. We identify the missing finite contribution---a nonlocal radial integral---whose inclusion restores exact thermodynamic consistency. Remarkably, this term is not an ad hoc correction: combined with the local Chern-Simons representative, it forms the transgression form, yielding a strictly gauge-invariant action. The correct action is therefore not the local Chern-Simons term alone but its transgression completion---a physical requirement rather than a mere mathematical refinement. The same mechanism persists for helical, rotating, scalarized, higher-derivative, and higher-dimensional black holes. Our work establishes that topological interactions can fundamentally alter the relation between the Euclidean action and the thermodynamic potential and identifies the gauge-invariant transgression form as the correct framework for black hole thermodynamics in Chern-Simons-coupled theories.

gr-qc↗

arXiv2026

Massive scalar fields in eccentric regime: Detectability and constraints from LISA observations of extreme mass-ratio inspirals

Extreme mass-ratio inspirals (EMRIs) are among the prime sources for future space-borne gravitational wave (GW) observatories and provide a useful setting for testing the presence of fundamental fields and possible deviations from general relativity (GR) in both strong and weak gravity regimes. In this work, we study the effect of a massive scalar field on eccentric equatorial EMRI dynamics around Kerr black holes. Considering that the inspiralling stellar-mass object carries a scalar charge and emits scalar radiation together with tensor GWs, we compute the relevant relativistic fluxes within the adiabatic treatment of the inspiral. With the solution of the scalar perturbation equation in the frequency domain, the resulting fluxes are presented through the Chebyshev interpolants in order to have the efficient inspiral evolution across the parameter space considered. We quantify the impact of scalar field mass and scalar charge on the orbital evolution and GW signal through phase shifts and waveform mismatches relative to both GR and the massless-scalar scenario. We find that massive scalar radiation can generate significant GW dephasing that increases with orbital eccentricity; however, the scalar flux is suppressed as the scalar field mass is becoming larger. Using a Fisher information matrix (FIM) analysis, we estimate the ability of Laser Interferometer Space Antenna (LISA) to measure or constrain the scalar charge and scalar field mass. Our results indicate that eccentric EMRIs can place meaningful constraints on massive scalar fields and provide a promising as well as important avenue for testing scalar-tensor extensions of gravity in the region of a strong gravitational field.

gr-qc↗

arXiv2026

Universally Diverging Grüneisen Ratio of Holographic Quantum Criticality

Quantum criticality is a hallmark of strongly correlated electron systems, as seen in heavy-fermion materials and high-temperature superconductors. Holographic duality provides a powerful framework to investigate these systems by translating them into weakly coupled classical gravity living in one higher dimension. Here, we harness this approach to study a field-induced quantum critical point with dynamical exponent $z=3$ in Einstein-Maxwell-Chern-Simons theory. Our analysis of its thermodynamic properties reveals a new universality class. Notably, we identify a diverging Grüneisen ratio with universal scaling $\sim T^{-2/3}$, a behavior that closely mirrors recent experiments on the heavy-fermion material CeRh$_6$Ge$_4$. These findings advance our understanding of metallic quantum criticality and highlight the potential of holographic duality as a tool for studying correlated quantum matters.

cond-mat.str-el↗

arXiv2025

Many-body chaos and pole-skipping in holographic charged rotating fluids

Recent developments identify pole-skipping as a `smoking-gun' signature of the hydrodynamic nature of chaos, offering an alternative way to probe quantum chaos in addition to the out-of-time-ordered correlator (OTOC). We study the quantum chaos and pole-skipping phenomenon in the strongly coupled charged rotating fluids, holographically dual to rotating black holes with nontrivial gauge field. We find that the near-horizon equation governing energy-density fluctuations differs from the source-less shock wave equation determining the OTOC, which depends on the $U(1)$ gauge choice. This discrepancy is eliminated under an appropriate boundary condition on the $U(1)$ gauge potential at the event horizon, as required by the vanishing of Wilson loop at the Euclidean horizon. We further investigate the dependence of the butterfly velocity on the charge and rotation parameters in a specific black hole configuration--the Cvetič-Lü-Pope solution.

hep-th↗

arXiv2025

Holographic study of shear viscosity and butterfly velocity for magnetic field-driven quantum criticality

We investigate the shear viscosity and butterfly velocity of a magnetic field-induced quantum phase transition in five dimensional Einstein-Maxwell-Chern-Simons theory, which is holographically dual to a class of strongly coupled quantum field theories with chiral anomalies. Our analysis reveals that the ratio of longitudinal shear viscosity to entropy density $η_\parallel/s$ exhibits a pronounced non-monotonic dependence on temperature $T$ when the magnetic field $B$ is slightly below the critical value $B_c$ of the quantum phase transition. In particular, it can develop a distinct minimum at an intermediate temperature. This contrasts sharply with the monotonic temperature scaling observed at and above $B_c$, where $η_\parallel/s$ follows the scaling $T^{2/3}$ at $B=B_c$ and transitions to $T^2$ for $B>B_c$ as $T\to0$. The non-vanishing of $η_\parallel/s$ for $B<B_c$ in the zero temperature limit suggests that it could serve as a good order parameter of the quantum phase transition. We also find that all butterfly velocities change dramatically near the quantum phase transition, and thus their derivatives with respect to $B$ can be independently used to detect the quantum critical point.

hep-th↗

arXiv2023

Properties of gapped systems in AdS/BCFT

We study the conductivities and entanglement structures of two different holographic gapped systems at zero density in the presence of boundaries within AdS/BCFT. The first gapped system is described by the Einstein-scalar gravity and the second one is the dual of AdS soliton geometry. We show that in both these two systems the bulk and boundary conductivities along the spatial direction of the boundary of BCFT are trivial. For the first system, when we increase the size of the subsystem the renormalized entanglement entropy is always non-negative and monotonically decreasing with discontinuous, or continuous, or smooth behavior, depending on the effective tension of the brane. While for the AdS soliton with a boundary, the renormalized entanglement entropy only exhibits a discontinuous drop when we increase the size of the subsystem.

hep-th↗

arXiv2016

Scalar waves from a star orbiting a BTZ black hole

In this paper we compute the decay rates of massless scalar waves excited by a star circularly orbiting around the non-extremal (general) and extremal BTZ black holes. These decay rates are compared with the corresponding quantities computed in the corresponding dual conformal field theories respectively. We find that matches are achieved in both cases.

hep-th↗