arXiv subjects

Zhou-Run Zhu

Publications and source records attributed to Zhou-Run Zhu.

17 recordsLinked to original sources

arXiv2026

Holographic spectral functions of exotic spin-1 mesons

We develop a general holographic framework for computing thermal spectral functions of exotic spin--1 mesons. A bulk Proca mass encodes the canonical ultraviolet dimension of the interpolating operator, allowing channels with different ultraviolet scaling to be treated within a unified membrane-flow formalism in the zero-spatial-momentum limit. We test this framework in a soft-wall model with a gluon-condensate background for the hybrid $\pi_1$ and tetraquark-like $Z_c$ channels. The results show that dissociation temperatures of both channels lie below the phase transition temperatures. Increasing $c$ delays dissociation in both channels, but through different effects: both the vacuum-mass shift and thermal spectral deformation contribute in the $\pi_1$ channel, whereas the latter dominates in the $Z_c$ channel. Nevertheless, for the same environment, the $Z_c$ resonance dissociates at a lower temperature than the $\pi_1$ resonance.

hep-ph↗

arXiv2026

Holographic light-quark energy loss in a spinning plasma

In this work, we investigate light-quark energy loss in a strongly coupled plasma described by a spinning black-brane background obtained from the large-black-hole limit of the Myers--Perry geometry. The parameter $a$ characterizes the boost/rotation of the dual fluid in this holographic setup and is related to the angular velocity in the corresponding limit. We employ two complementary probes, the falling-string and shooting-string descriptions, to compute the stopping distance and the instantaneous energy loss of a light quark moving either transverse or parallel to the rotation axis. The results show that light quarks thermalize more readily in a hot environment. For parallel propagation, a counter-propagating configuration facilitates thermalization, whereas a co-propagating configuration suppresses it. For transverse propagation, increasing the magnitude of the rotational motion promotes thermalization. In addition, the instantaneous energy loss increases along the trajectory of the endpoint.

hep-ph↗

arXiv2026

Holographic entanglement entropy under external magnetic field from the EMD model

In this work, we explore holographic entanglement entropy in the QCD phase diagram under an external magnetic field using an Einstein-Maxwell-dilaton model. We consider both the specious-confinement and deconfined phases. In the perpendicular magnetic field orientation, the strip length shows three distinct branches, and the entanglement entropy develops a swallow-tail structure, indicating a transition between connected and disconnected entanglement surfaces. For the parallel orientation, the behavior is monotonic and no transition occurs. In addition, the difference in entanglement entropy changes smoothly with temperature at small chemical potential, but becomes multivalued at large chemical potential. Increasing the magnetic field restores single-valued behavior. These results are consistent with the black hole thermodynamics and the QCD phase diagram. Our findings show that entanglement entropy can serve as an effective probe of the QCD phase transition.

hep-th↗

arXiv2026

Gravitational waves from holographic first-order QCD phase transition with magnetic field

In this paper, we investigate the generation of gravitational waves (GWs) from a first-order QCD confinement-deconfinement phase transition under external magnetic field from holography. We analyze the GWs spectra across both hard wall and soft wall models for Jouguet detonations and non-runaway scenarios. Our results indicate that increasing the magnetic field shifts the spectral peak to lower frequencies. The predicted GWs signals are potentially detectable by observatories such as IPTA, SKA, BBO and NANOGrav. Decomposing the spectra reveals that sound waves typically dominate the signal around the peak frequency, bubble collisions prevail at spectral extremities, and the contribution from MHD turbulence is significant only for non-runaway bubble scenarios at high frequencies. This work suggests that magnetized QCD phase transitions are viable cosmological sources for observable GW backgrounds, offering a potential pathway to constrain primordial magnetic fields through future PTA observations.

hep-ph↗

arXiv2026

Effective running coupling constant and jet quenching parameter in the spinning background from holography

In this work, we study the effective running coupling constant of heavy quark pair and jet quenching parameter in the spinning background. Ultra-locally, the boosted fluid is described by the boosted parameter and dual to a globally rotating system. Our results show that the angular momentum suppresses the effective running coupling constant and reduces its maximum value. The results demonstrate that the angular momentum promotes the dissociation of quarkonium and has a stronger effect on the effective running coupling constant when the axis of $Q\overline{Q}$ is transverse to the direction of the angular momentum. We also find that the angular momentum enhances the jet quenching parameter and has a stronger effect when the jet moves transversely to the direction of the angular momentum, namely $\hat{q}_{\perp}> \hat{q}_{\parallel}$. We discuss the dependence of the jet quenching parameter on the $η/s$ at strong coupling in the presence of the angular momentum.

hep-ph↗

arXiv2025

Exploring Transport Properties of Quark-Gluon Plasma in Flavor-Dependent Systems with a Holographic Model

Based on the holographic model, which incorporates the equation of state (EoS) and baryon number susceptibility for different flavors, we calculate the drag force, jet quenching parameter, and diffusion coefficient of the heavy quark at finite temperature and chemical potential. The holographic results for the diffusion coefficient align with lattice data for $N_f = 0$ and $N_f = 2+1$, falling within their error margins. The holographic diffusion coefficient for heavy quark in the systems of different flavors \textcolor{red}{is compatible with estimates from ALICE data.} The jet quenching parameter in our model demonstrates strong consistency \textcolor{red}{with the estimations obtained from Bayesian analysis of data from both RHIC and LHC for different flavors.} We can confirm the model provides a good description of the transport properties of QGP. The work reinforces the potential of bottom-up holographic model in advancing our understanding of transport properties of hot and dense quark-gluon plasma.

hep-ph↗

arXiv2025

Imaginary potential and thermal width in the spinning black hole background from holography

In this study, we investigate the imaginary potential of heavy quarkonium in the spinning black hole background. Then we estimate the thermal width, which is determined by the imaginary part of the finite temperature potential. In the ultra-local description, the boosted fluid represents a globally rotating fluid. Using a holographic approach, we systematically analyze how boost parameter influences these quantities. Our results reveal that increasing boost parameter causes the imaginary potential to emerge at smaller interquark distances, suggesting that boost parameter accelerates quarkonium melting. Furthermore, we find that boost parameter enhances the thermal width, indicating greater instability of the bound state at higher boost parameter. Notably, we observe that the effect of boost parameter on quarkonium dissociation is more pronounced when the axis of the quark-antiquark pair is transverse to the direction of boost parameter.

hep-ph↗

arXiv2025

$R^2$ corrections to holographic heavy meson dissociation

In this paper, we investigate the $R^2$ corrections to the dissociation of heavy quarkonium in the Gauss-Bonnet gravitational background. We analyze the impact of Gauss-Bonnet parameter $λ_{GB}$ on the spectral function of charmonium and bottomonium, and examine how $λ_{GB}$ affects the dissociation of heavy quarkonium. Our results show that $λ_{GB}$ reduces the peak height and increases the peak width of the spectral function, suggesting that $λ_{GB}$ enhances the dissociation of heavy quarkonium. We also discuss how the dissociation of heavy quarkonium varies with the ratio of shear viscosity to entropy density and find the dissociation will be easier in more perfect plasma. Additionally, we observe that the temperature decreases the peak height and widens the peak, thereby accelerating the dissociation.

hep-ph↗

arXiv2024

Thermodynamics of heavy quarkonium in the spinning black hole background

In this paper, we examine the thermodynamics of heavy quarkonium in the spinning black hole background. Specifically, we investigate the effect of angular momentum on the interquark distance, free energy, binding energy, entropy, entropic force, and internal energy of heavy quarkonium from the thermodynamic relationship. Our findings indicate that the angular momentum reduces the maximum value of interquark distance, suggesting that it promotes the dissociation of quarkonium. Additionally, we observe that the angular momentum suppresses free energy. From the results of binding energy, the angular momentum favors the melting of meson into a free quark and antiquark. Moreover, the results show that angular momentum increases the entropy and entropic force, thus accelerates the dissociation of quarkonium. The angular momentum increases the internal energy at large interquark distance. Finally, we find that the angular momentum has a more pronounced effect on quarkonium when the axis of quark pair $Q\overline{Q}$ is transverse to the direction of angular momentum.

hep-ph↗

arXiv2024

Heavy quarkonium spectral function in the spinning black hole background

In this paper, we study the dissociation of heavy quarkonium in the spinning black hole background. Specifically, we analyze the spectral function of charmonium and bottomonium in the spinning black hole background and examine how the angular momentum affects the dissociation of $J/Ψ$ and $Υ(1S)$. From the results, we find that the angular momentum and temperature decreases the peak height and expands the peak width of the spectral function, thereby enhancing the dissociation of heavy vector mesons. Moreover, the angular momentum has a stronger dissociation effect in the transverse orientation, revealing the directional influence of angular momentum.

hep-ph↗

arXiv2024

Inverse magnetic catalysis and energy loss in holographic QCD model

In this paper, we consider the Einstein-Maxwell-dilaton holographic model for light quarks with nonzero magnetic field and chemical potential. First, we study the phase diagrams in $T-μ$ and $T-B$ planes. We observe inverse magnetic catalysis which is consistent with the lattice QCD results. We discuss the influence of the magnetic field and chemical potential on the location of the critical end point (CEP). It is found that the magnetic field increases the critical $μ_{\scriptscriptstyle CEP}$ of the CEP in the $T-μ$ plane and the chemical potential increases the critical $B_{\scriptscriptstyle CEP}$ of the CEP in the $T-B$ plane. Second, we discuss the equations of state (EOS) with nonzero magnetic field and chemical potential. We observe that the EOS near the phase transition temperature are nonmonotonic. Then we study the energy loss with a nonzero magnetic field and chemical potential. It is found that the drag force of the heavy quark and jet quenching parameter $\hat{q}$ show an enhancement near the phase transition temperature. The peak values of drag force and $\hat{q}$ are pushed toward lower temperature with increasing $B$ or $μ$. This phenomenon is consistent with the phase transition temperature decrease with increasing $B$ or $μ$ in this holographic model. Moreover, we find that the heavy quark may lose more energy when it is perpendicular to a magnetic field which is consistent with the results of the jet quenching parameter.

hep-ph↗

arXiv2024

Gravitational waves from holographic QCD phase transition with gluon condensate

In this paper, we discuss the holographic first order QCD phase transition with gluon condensate and the generation of gravitational waves (GWs) from the phase transition. The first order QCD phase transition is dual to the first order Hawking-Page phase transition from holography. We study the first order Hawking-Page phase transition from the thermal dilatonic phase to the dilatonic black hole phase and find the phase transition temperature is proportional to the gluon condensate. After substituting into the phenomenological value of gluon condensate from QCD sum rules, we find $T_c=155.38\ MeV$. In further research, we study the GWs generated from holographic cosmic first order QCD phase transition with gluon condensate and the produced GWs might be detected by the International Pulsar Timing Array, Square Kilometre Array and Big-Bang Observer. Moreover, the gluon condensate suppresses the energy density of total GWs and peak frequency.

hep-ph↗

arXiv2022

Thermodynamics and energy loss in D dimensions from holographic QCD model

We consider the holographic QCD model with a planar horizon in the D dimensions with different consistent metric solutions. We investigate the black hole thermodynamics, phase diagram and equations of state (EoS) in different dimensions. The temperature and chemical potential dependence of the drag force and diffusion coefficient also have been studied. From the results, the energy loss of heavy quark shows an enhancement near the phase transition temperature in D dimensions. This finding illustrates that the energy loss of heavy quark has a nontrivial and non-monotonic dependence on temperature. Furthermore, we find the heavy quark may lose less energy in higher dimension. The diffusion coefficient is larger in higher dimension.

hep-ph↗

arXiv2021

Holographic Schwinger effect in the dynamical AdS/QCD model

In this paper, we discuss the potential analysis of the holographic Schwinger effect in the bottom up AdS/QCD model. We study the effect of the magnetic field on the critical field and total potential in finite chemical potential case. By evaluating the critical electric field from the DBI action, one can observe that magnetic field decreases critical electric field Ec. From the results of potential analysis, we find the magnetic field reduces the potential barrier and favor the Schwinger effect which agrees with the results of the critical electric field. Moreover, the Schwinger effect is more obvious when pairs are parallel to the magnetic field than that in perpendicular case in this Einstein-Maxwell-dilaton model.

hep-ph↗

arXiv2020

Potential analysis of holographic Schwinger effect in the magnetized background

We study the holographic Schwinger effect with magnetic field at RHIC and LHC energies by using the AdS/CFT correspondence. We consider both weak and strong magnetic field cases with $B\ll T^2$ and $B\gg T^2$ solutions respectively. Firstly, we calculate separating length of the particle pairs at finite magnetic field. It is found that for both weak and strong magnetic field solutions the maximum value of separating length decreases with the increase of magnetic field , which can be inferred that the virtual electron-positron pairs become real particles more easily. We also find that the magnetic field reduces the potential barrier and the critical field for the weak magnetic field solution, thus favors the Schwinger effect. With strong magnetic field solution, the magnetic field enhances the Schwinger effect when the pairs are in perpendicular to the magnetic field although the magnetic field increases the critical electric field.

hep-ph↗

arXiv2020

The effect of gluon condensate on imaginary potential and thermal width from holography

By the use of the gauge/gravity duality, we calculate the imaginary part of heavy quarkonium potential and thermal width with the effect of gluon condensate which is absent in AdS$_{5}$ background. Our results show that the dropping gluon condensate reduces the absolute value of imaginary potential and therefore decreases the thermal width both in "exact" and "approximate" approach implying that the heavy quarkonium has a weaker bound with the increase of gluon condensate. In addition, the thermal width will disappear at a critical condensate value, which indicates the dissociation of quarkonium. We conclude that increasing gluon condensate will lead to easier dissociation of heavy quarkonium for fixed temperature.

hep-ph↗

arXiv2019

Energy loss of heavy and light quarks in holographic magnetized background

We systematically study holographic effects on the magnetic field dependence of the drag force, diffusion coefficient, jet quenching parameter of heavy quarks and the shooting string energy loss of light quarks in the RHIC and LHC energy regions by using the AdS/CFT correspondence in this paper. This study is motivated by the phenomena of strong magnetic field and jet quenching, which have been found in relativistic heavy ion collisions. The probe's direction of motion is perpendicular and parallel to the direction of magnetic field $B$. The effects of magnetic field on energy loss when moving perpendicular to the magnetic field direction are larger than moving parallel to the magnetic field direction, which implies that the magnetic field tends to suppress more quarks and jets when moving in the transverse direction than in the parallel direction. It is found that the diffusion coefficient decreases with the magnetic field in the transverse direction, but increases with the magnetic field in the parallel direction, which indicates that the quark may diffuse farther when moving parallel to the magnetic field direction. We also find that the magnetic field will enhance the energy loss of the light quarks when moving in the transverse direction than in the parallel direction.

hep-ph↗