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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., Comment: 16 pages, 6 figures

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 $J/\Psi$ and $\Upsilon(1S)$. From the results, we find that the angular momentum decreases the peak height and expands the peak width of the spectral function which indicates it enhances 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., Comment: 12 pages, 2 figures

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 agrees with the fitting results of ALICE data well. The jet quenching parameter in our model demonstrates strong consistency with the results from both RHIC and LHC for different flavors. By comparing the experimental data with other models, we can confirm the validity of our holographic model calculation. The work reinforces the potential of bottom-up holographic model in advancing our understanding of transport properties of hot and dense quark-gluon plasma.

Utilizing the Stern-Gerlach apparatus to create matter-wave superposition states is a long-sought-after goal, not only due to its potential applications in the quantum realm but also because of its fundamental implications for studying the quantum properties of gravity. The main challenge in creating a macroscopic quantum interferometer arises from the loss of coherence, primarily through two channels. One channel involves strong coupling with the environment for macroscopic matter, leading to decoherence. The other channel relates to the precision of wave packet overlap, which can occur due to external and internal fluctuations of various sources. The latter introduces a unique challenge for larger-scale masses by perturbing the centre of mass motion of the macroscopic object. Here, we study a particular challenge, namely, the issue of internal degrees of freedom, specifically phonon fluctuations and contrast reduction. This work will investigate the contrast reduction caused by spin-magnetic field and diamagnetic interactions at the phonon occupation level in the quantum gravity-induced entanglement of masses (QGEM) protocol configuration.

In this paper, we study the $R^2$ corrections to the spectral functions of heavy mesons in Gauss-Bonnet gravity. We discuss the effect of Gauss-Bonnet parameter $\lambda_{GB}$ on the 1S states and 2S states of charmonium and bottomonium. It is found that $\lambda_{GB}$ reduces the height and increases the width of the 1S states peak. The 2S states of charmonium and bottomonium dissociate gradually as increasing $\lambda_{GB}$. It is obvious that $\lambda_{GB}$ enhances the dissociation of charmonium and bottomonium., Comment: 13 pages, 4 figures

In this paper, we consider an Einstein-Maxwell-dilaton holographic model for light quarks with nonzero magnetic field and chemical potential. The phase diagram in $T-\mu$ and $T-B$ planes are obtained. We observe the inverse magnetic catalysis (IMC) which is consistent with the lattice results. We discuss the influences of magnetic field and chemical potential on the location of critical endpoint (CEP). We find magnetic field increases critical $\mu_{\scriptscriptstyle CEP}$ of CEP in $T-\mu$ plane and chemical potential increases critical $B_{\scriptscriptstyle CEP}$ of CEP in $T-B$ plane. In further research, we observe the equations of state (EoS) near the phase transition temperature are non-monotonic. From the results of energy loss, we find that the drag force of heavy quark and jet quenching parameter behave an enhancement near the phase transition temperature. The peak values of drag force and $\hat{q}$ are pushed towards lower temperature when increasing $B$ or $\mu$. This phenomenon is consistent with the phase transition temperature decreases with increasing $B$ or $\mu$ in this holographic model. Moreover, we find heavy quark may lose more energy when perpendicular to magnetic field which is consistent with the results of jet quenching parameter., Comment: 29 pages, 22 figures

Creating a massive spatial quantum superposition, such as the Schr\"odinger cat state, where the mass and the superposition size within the range $10^{-19}-10^{-14}$ kg and $\Delta x \sim 10~{\rm nm}-100~\mu {\rm m}$, is a challenging task. The methods employed so far rely either on wavepacket expansion or on a quantum ancilla, e.g. single spin dependent forces, which scale inversely with mass. In this paper, we present a novel approach that combines gravitational acceleration and diamagnetic repulsion to generate a large spatial superposition in a relatively short time. After first creating a modest initial spatial superposition of $1~\mu {\rm m}$, achieved through techniques such as the Stern-Gerlach (SG) apparatus, we will show that we can achieve an $\sim 10^{2}-10^{3}$ fold improvement to the spatial superposition size ($1~{\rm \mu m}\rightarrow 980~\mu {\rm m}$) between the wave packets in less than $0.02$~s by using the Earth's gravitational acceleration and then the diamagnetic repulsive scattering of the nanocrystal, neither of which depend on the object mass. Finally, the wave packet trajectories can be closed so that spatial interference fringes can be observed. Our findings highlight the potential of combining gravitational acceleration and diamagnetic repulsion to create and manipulate large spatial superpositions, offering new insights into creating macroscopic quantum superpositions., Comment: 10 pages, 3 figures

Placing a large mass in a large spatial superposition, such as a Schr\"odinger Cat state is a significant and important challenge. In particular, the large spatial superposition (${\cal O}(10-100)$ $\mu$m) of mesoscopic masses ($m\sim {\cal O}(10^{-14} -10^{-15})$ kg) makes it possible to test the quantum nature of gravity via entanglement in the laboratory. To date, the proposed methods of achieving this spatial delocalization are to use wavepacket expansions or quantum ancilla (for example spin) dependent forces, all of whose efficacy reduces with mass. Thus increasing the spatial splitting independent of the mass is an important open challenge. In this paper, we present a method of achieving a mass-independent enhancement of superposition via diamagnetic repulsion from current-carrying wires. We analyse an example system which uses the Stern-Gerlach effect to creating a small initial splitting, and then apply the diamagnetic repulsion method to enhance the superposition size ${\cal O}(400-600)$ $\mu$m from an initial modest split of the wavefunction. We provide an analytic and numeric analysis of our scheme., Comment: 12 pages, 4 figures

Large spatial quantum superposition of size ${\cal O}(1-10)~{\rm \mu \text{m}}$ for mass $m \sim 10^{-17}-10^{-14}~\text{kg}$ is required to probe the foundations of quantum mechanics and testing classical and quantum nature of gravity via entanglement in a laboratory. In this paper, we will show that it is possible to accelerate the two spin states of a macroscopic nano-crystal sourced by the inhomogeneous nonlinear magnetic field in the Stern-Gerlach type setup. We will assume that the electronic spin can be embedded at the centre of the nano-crystal, such as the nitrogen-vacancy (NV) centre of diamond. Our analysis will be generic to any dopant or any material. We will show that we can create a desired superposition size within $1-2$ seconds by catapulting the trajectories of the two spin states with a modest magnetic field gradient and then recombine the trajectories for a coherent interference. We will show the demanding nature of the precision required in the magnetic field to recover $99\%$ spin coherence confidence level at the moment of interference., Comment: 18 pages, 16 figures

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., Comment: 16 pages, 2 figures

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., Comment: 31 pages, 17 figures, version accepted for publication in European Physical Journal C

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., Comment: 16 pages, 4 figures

By treating the order parameter as a stochastic thermal fluctuating variable for small-large black hole phase transition, we investigate the kinetic process of phase transition for the Kerr-AdS (anti-de Sitter) black holes on free energy landscape. We find that the extremal points of the off shell Gibbs free energy correspond to physical black holes. For small-large black hole phase transition, the off shell Gibbs free energy exhibits a double well behavior with the same depth. Contrary to previous research for the kinetics of phase transition for the Kerr-Newman-AdS family black holes on a free energy landscape, we find that there is a lower bound for the order parameter and the lower bound corresponds to extremal black holes. In particular, the off shell Gibbs free energy is zero instead of divergent as previous work suggested for vanishing black hole horizon radius, which corresponds to the Gibbs free energy of a thermal AdS space. The investigation for the evolution of the probability distribution for the phase transition indicates that the initial stable small (large) black hole tends to switch to stable large (small) black hole. Increasing the temperature along the coexistence curve, the switching process becomes faster and the probability distribution reaches the final stationary Boltzmann distribution at a shorter time. The distribution of the first passage time indicates the time scale of the small-large black hole phase transition, and the peak of the distribution becomes sharper and shifts to the left with the increase of temperature along the coexistence curve. This suggests that a considerable first passage process occurs at a shorter time for higher temperature. The investigation of the kinetics of phase transition might provide us new insight into the underlying microscopic interactions., Comment: 16 pages, 10 figures, published version

In this paper, we study the small-large black hole phase transition and construct the Ruppeiner geometry for the five-dimensional charged Gauss-Bonnet-AdS black hole in the grand canonical ensemble. By making use of the equal area law, we obtain the analytical coexistence curve of the small and large black holes. Then the phase diagrams are examined. We also calculate the change of the thermodynamic volume during the small-large phase transition, which indicates that there exists a sudden change among the black hole microstructures. The corresponding normalized scalar curvature of the Ruppeiner geometry is also calculated. Combing with the empirical observation of scalar curvature, we find that for low electric potential, the attractive interaction dominates among the microstructures, while a high electric potential produces repulsive interactions. In the reduced parameter space, we observe that only attractive interaction is allowed when the coexistence region is excluded. The normalized scalar curvature also admits a critical exponent 2 and a universal constant $-\frac{1}{8}$. In particular, the value of the normalized scalar curvature keeps the same along the coexistence small and large black hole curves. So in the grand canonical ensemble, the interaction can keep constant at the phase transition where the black hole microstructures change. These results disclose the intriguing microstructures for the charged AdS black hole in the Gauss-Bonnet gravity., Comment: 16 pages and 8 figures

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., Comment: 21 pages with 9 figures in Revtex; one new section and 4 figures added

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., Comment: 6 pages, 6 figures

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., Comment: 26 pages, 8 figures

We study the equal area law and charge-electric potential criticality for the charged Anti-de Sitter black holes. Considering that the black hole charge is a double-valued function of the electric potential, we investigate the equal area law in detail. We find that the equal area law has two different expressions when the thermodynamic quantities are near the critical point and far from the critical point. For these two different cases, we obtain the analytical coexistence curve for the low and high electric potential black hole phases by using these two expressions of the equal area law. Based on the result, we analytically study the phase diagram and the critical phenomena in the charge-electric potential plane., Comment: 10 pages, 3 figures, structures are re-organized