arXiv subjects

Defu Hou

Publications and source records attributed to Defu Hou.

At least 37 records · Page 2Linked to original sources

arXiv2025

Functional renormalization group study of the quark-meson model with omega and rho vector mesons

We employ the functional renormalization group flow equations to investigate the phase structure of the two-flavor quark-meson model in the presence of a finite isospin chemical potential, incorporating interactions with omega and rho vector mesons. For comparison, we also compute the phase diagram in the chiral limit using the mean-field approximation. Our findings demonstrate that omega and rho mesons affect the phase structure in markedly distinct ways, and the introduction of an isospin chemical potential leads to significant modifications in the phase boundaries and critical region. Increasing the isospin chemical potential lowers the tricritical points temperature, and tends to suppress the unphysical ``back-bending" of the FRG phase boundary at low temperature.

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arXiv2025

Strong Coupling Expansion of Gluodynamics on a Lattice under Rotation

The analytic strong coupling expansion of the gluodynamics under a rotation with an angular velocity $ω$ is reported. While the expansion is systematic, free from additional assumptions, the deconfinement temperature determined by the onset of the Polyakov loop expectation value decreases with the angular velocity up to $ω^2$, opposite to the tendency found in numerical simulations. As a by-product, a simple formula is obtained for the $ω^2$ coefficient of the deconfinement temperature shift in terms of the latent heat and the discontinuity of the moment of inertia at the transition without rotation. This formula is independent of the strong coupling and may benefit further investigation of the subject.

hep-ph↗

arXiv2025

Generalized relativistic second-order spin hydrodynamics from Zubarev's non-equilibrium statistical operator

Inspired by the work in Ref.[1], which considers the additional second-order contributions arising from nonlocal corrections due to two-point correlation functions of tensors of different ranks at distinct spacetime points, we similarly employ the nonequilibrium statistical operator method to extend this framework to include spin degrees of freedom. In addition to obtaining analogous extra second-order terms in the shear stress tensor, bulk viscous pressure, and charge diffusion currents resulting from such contributions, we further derive additional second-order terms originating from the same mechanism in the charge diffusion currents, rotational stress tensor and the boost heat vector. Furthermore, we express all transport coefficients represented by two-point or three-point correlations in terms of retarded Green's functions.

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arXiv2025

Relativistic second-order spin hydrodynamics: A Kubo-type formulation for the quark-gluon plasma

Building upon Zubarev's nonequilibrium statistical operator formalism, we derive a relativistic canonical-like second-order spin hydrodynamics for two power-counting schemes. We obtain comprehensive second-order expressions for dissipative fluxes, including the shear stress tensor, bulk viscous pressure, charge-diffusion currents, rotational stress tensor, boost heat vector, and spin tensor-related dissipative flux. By introducing novel transport coefficients and expressing them in terms of equilibrium correlation functions, we establish new Kubo-type formulas for second-order transport. Our findings have significant implications for understanding the collective spin dynamics of strongly interacting matter and provide a robust theoretical basis for future experimental and theoretical studies.

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arXiv2025

The nucleon structure from an AdS/QCD model in the Veneziano limit

We employ the VQCD model, a holographic approach that dynamically simulates essential QCD characteristics, including linear mass spectra, confinement, asymptotic freedom, and magnetic charge screening, while incorporating quark flavor effects. Using this model, we first calculate the proton mass spectrum and the wave function, incorporating anomalous dimensions to refine our results. Next, we compute the proton structure functions across a range of Bjorken $x$ values using consistent parameters. Furthermore, we derive the proton electromagnetic form factor by solving the electromagnetic field's motion equation, accounting for background effects, and demonstrate qualitative consistency with results from free electromagnetic fields coupled to fermions. Finally, we calculate the gravitational form factors by introducing an effective graviton mass $m$ arising from chiral symmetry breaking and the proton energy-momentum tensor. Our calculations yield results that are in excellent agreement with experimental data and lattice QCD computations, validating the VQCD model as a robust tool for studying proton properties.

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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.

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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

Holographic spin alignment of $J/ψ$ meson in magnetized plasma

We study the mass spectra and spin alignment of vector meson $J/ψ$ in a thermal magnetized background using a generalized theoretical framework based on gauge/gravity duality. Utilizing a soft wall model for the QGP background and a massive vector field for the $J/ψ$ meson, we delve into the meson's spectral function and spin parameters $(λ_θ,\, λ_φ,\,λ_{θφ})$ for different cases, assessing their response to variations in magnetic field strength, momentum, and temperature. We initially examine scenarios where a meson's momentum aligns parallel to the magnetic field in helicity frame. Our results reveal a magnetic field-induced positive $λ_θ^\text{H}$ for low meson momentum, transitioning to negative with increased momentum. As a comparison, we also study the case of momentum perpendicular to the magnetic field and find the direction of magnetic field does not affect the qualitative behavior for the $eB$-dependence of $λ_θ^\text{H}$. Moreover, we apply our model to real heavy-ion collisions for three different spin quantization directions. Further comparisons with experimental data show qualitative agreement for spin parameters $λ_θ$ and $λ_φ$ in the helicity and Collins-Soper frames.

hep-ph↗

arXiv2024

Holographic spin alignment for vector mesons

We develop a general framework for studying the spin alignment $ρ_{00}$ for flavorless vector mesons by using the gauge/gravity duality. Focusing on the dilepton production through vector meson decay, we derive the relation between production rates at each spin channel and meson's spectral function, which can be evaluated by holographic models for a strongly coupled system. As examples, we study $ρ_{00}$ for $J/ψ$ and $ϕ$ mesons, induced by the relative motion to a thermal background, within the soft-wall model. We show that $ρ_{00}$ in the helicity frame for $J/ψ$ and $ϕ$ mesons have positive and negative deviations from 1/3 at $T=150$ MeV, respectively, which consequently leads to different properties for their global spin alignments.

hep-ph↗

arXiv2024

Configuration entropy of $Υ(1S)$ state in strong coupling plasma

To better understand the effects of strong coupling and QCD at high temperature in QGP, by using holographic model, we investigate the dissociation effect of bottomonium under the higher-order curvature corrections to the supergravity action corresponding to the corrections of large N expansion of boundary CFT in the side of field theory. The results show that effective potential is not a good physical quantity to estimate the dissociation strength of bottomonium in the case of finite wave number and considering the higher-order curvature corrections. Therefore, we calculate the quasinormal spectra(QNMs) and the differential configuration entropy(DCE). It is found that the dissociation effect is stronger for the stronger coupling.

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↗

arXiv2024

Mass splitting and spin alignment for $ϕ$ mesons in a magnetic field in NJL model

Based on the Nambu-Jona-Lasinio (NJL) model, we develop a framework for calculating the spin alignment of vector mesons and applied it to study $ϕ$ mesons in a magnetic field. We calculate mass spectra for $ϕ$ mesons and observe mass splitting between the longitudinally polarized state and transversely polarized states. The $ϕ$ meson in a thermal equilibrium system is preferred to occupy the state with spin $λ=0$ than those with spin $λ=\pm1$, because the former state has a smaller energy. As a consequence, we conclude that the spin alignment will be larger than 1/3 if one measures along the direction of the magnetic field, which is qualitatively consistent with the recent STAR data. Around the critical temperature $T_{C}=150$ MeV, the positive deviation from 1/3 is proportional to the square of the magnetic field strength, which agrees with the result from the non-relativistic coalescence model. Including the anomalous magnetic moments for quarks will modify the dynamical masses of quarks and thus affect the mass spectra and spin alignment of $ϕ$ mesons. The discussion of spin alignment in the NJL model may help us better understand the formation of hadron's spin structure during the chiral phase transition.

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arXiv2024

Phase structure and critical phenomena in 2-flavor QCD by holography

We explore the phase structure of Quantum Chromodynamics (QCD) with two dynamical quark flavors at finite temperature and baryon chemical potential, employing the non-perturbative gauge/gravity duality approach. Our gravitational model is tailored to align with state-of-the-art lattice data regarding the thermal properties of multi-flavor QCD. Following a rigorous parameter calibration to match equations of state and the QCD trace anomaly at zero chemical potential derived from cutting-edge lattice QCD simulations, we investigate thermodynamic quantities and order parameters. We predict the location of the critical endpoint (CEP) at $(μ_{\text{CEP}}, T_{\text{CEP}})=(219,182)$ MeV at which a line of first-order phase transitions terminate. We compute critical exponents associated with the CEP and find that they almost coincide with the critical exponents of the quantum 3D Ising model.

hep-ph↗

arXiv2023

The photon production and collective flows from magnetic induced gluon fusion and splitting in early stage of high energy nuclear collision

We present an event-by-event study of photon production in early stage of high energy nuclear collisions, where the system is dominant by highly occupied of gluons and initialized by McLerran-Venugopalan model. The photons are produced through the gluon fusion and splitting processes when strong magnetic field is included. We study the spectra and collective flows of the photons and show their dependence on transverse momentum $q_{T}$. It is found that in our approach the photons from boost invariant evolving glasma provide visible enhancement on spectrum and obvious contribution on $v_{2}$ of the total direct photons. The results, by weighting on top of parton-hadron-string dynamics (PHSD) model, agree even better with experiment measurements in Au-Au 20\%-40\% centrality collisions at $\sqrt{s_{NN}}=200$GeV.

hep-ph↗

arXiv2023

$J/Ψ$ suppression in a rotating magnetized holographic QGP matter

We study the dissociation effect of $J/Ψ$ in magnetized, rotating QGP matter at finite temperature and chemical potential using gauge/gravity duality. By incorporating angular velocity into the holographic magnetic catalysis model, we analyze the influence of temperature, chemical potential, magnetic field, and angular velocity on the properties of $J/Ψ$ meson. The results reveal that temperature, chemical potential, and rotation enhance the dissociation effect and increase the effective mass in the QGP phase. However, the magnetic field suppresses dissociation, and its effect on the effective mass is non-trivial. Additionally, we explore the interplay between magnetic field and rotation, identifying a critical angular velocity that determines the dominant effect. As a parallel study, we also examine the rotation effect in the holographic inverse magnetic catalysis model, although the magnetic field exhibits distinctly different behaviors in these two models, the impact of rotation on the dissociation effect of $J/Ψ$ is similar. Finally, we investigate the influence of electric field and demonstrate that it also speeds up the $J/Ψ$ dissociation.

hep-ph↗

arXiv2023

Vector meson spectral function in a dynamical AdS/QCD model

By using gauge/gravity duality, we calculate the spectral function of the heavy vector mesons with the presence of an intense magnetic field in a hot and dense medium. The results show that, a general conclusion, as the increases of magnetic field, chemical potential and temperature, the height of the peak of the spectral function decreases and the width increases. A nontrivial result is the change from the peak position of spectral function. We explain this non-trivial behavior by the interplay of the interaction between the two heavy quarks and the interaction between the medium with each of the heavy quarks.

hep-ph↗

arXiv2023

Phase diagram of holographic thermal dense QCD matter with rotation

We study the rotation effects of the hot and dense QCD matter in a non-perturbative regime by the gauge/gravity duality. We use the gravitational model that is designated to match the state-of-the-art lattice data on the thermal properties of (2+1)-flavor QCD and predict the location of the critical endpoint and the first-order phase transition line at large baryon chemical potential without rotation. After introducing the angular velocity via a local Lorentz boost, we investigate the thermodynamic quantities for the system under rotation in a self-consistent way. We find that the critical temperature and baryon chemical potential associated with the QCD phase transition decrease as the angular velocity increases. Moreover, some interesting phenomena are observed near the critical endpoint. We then construct the 3-dimensional phase diagram of the QCD matter in terms of temperature, baryon chemical potential, and angular velocity. As a parallel investigation, we also consider the gravitational model of $SU(3)$ pure gluon system, for which the 2-dimensional phase diagram associated with temperature and angular velocity has been predicted. The corresponding thermodynamic quantities with rotation are investigated.

hep-ph↗

arXiv2023

De Haas - van Alphen Effect under Rotation

We explored the interplay between magnetic field and rotation in the de Hass - van Alphen oscillation. The effect is found to be reduced because of the re-weighting of different states within the same Landau level by rotation energy. The implications of our results on high energy physics and condensed matter physics are speculated.

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