arXiv subjects

Zhong-Wen Feng

Publications and source records attributed to Zhong-Wen Feng.

At least 19 recordsLinked to original sources

arXiv2026

Matter-induced global regularity in non-polynomial quasi-topological gravity with Born-Infeld electrodynamics

We construct exact static, spherically symmetric charged solutions in four-dimensional non-polynomial quasi-topological gravity coupled to Born-Infeld electrodynamics. We focus on the model $h(p)=p/(1+\ell^{2}p)$, whose vacuum branch develops a curvature singularity at a finite radius. We show that Born-Infeld nonlinearities can remove this singularity within a finite region of parameter space, yielding globally regular geometries with an asymptotically flat exterior and a finite-curvature AdS-type core. The regular sector contains both horizonless configurations and RBHs, separated by a degenerate-horizon boundary. We further identify a continuous branch of regular black holes with a triple-degenerate inner horizon and a simple outer event horizon, satisfying $κ_-=0$ and $κ_+\neq0$. These results provide a converse example to cases in which introducing charge spoils the regularity of a black hole that is regular in vacuum. In the present model, Born-Infeld electrodynamics instead removes the finite-radius singularity of a gravitational branch that is singular in vacuum and supports globally regular charged geometries, including regular black holes with nontrivial inner-horizon structure.

gr-qc↗

arXiv2026

Quasinormal modes response to thermodynamic phase transitions in the charged AdS black hole surrounded by perfect fluid dark matter

We investigate how thermodynamic phase transitions are reflected in the quasinormal modes (QNMs) of charged anti-de Sitter (AdS) black holes surrounded by perfect fluid dark matter (PFDM). In the extended phase space, increasing the positive PFDM parameter raises the critical temperature and pressure while reducing the critical horizon radius. We compute the fundamental QNMs of a massless scalar perturbation using a Chebyshev pseudospectral method and analyze their evolution along isobaric and isothermal processes below the critical point. The small and large black hole branches trace clearly separated QNM trajectories and display sharply different slopes near the first-order transition, providing a dynamical signature of the branch change. Along isotherms, this evolution results from the competing effects of the horizon radius and pressure, or equivalently the AdS radius, rather than from the horizon radius alone. At the critical point, however, the QNM frequencies vary smoothly with the horizon radius and show no sharp signature of the second-order transition. Along the coexistence curve, the separation between the small and large black hole QNMs decreases as the Gibbs free energy swallowtail shrinks and vanishes at criticality. These results show that PFDM shifts both the thermodynamic phase structure and the associated QNM response, while the fundamental scalar QNM spectrum remains sensitive to the first-order small/large black hole transition.

gr-qc↗

arXiv2026

Regular black hole with sub-Planckian curvature and suppressed exponential mass inflation

We construct a static spherically symmetric regular black hole with a Minkowski core, and a degenerate inner horizon with vanishing surface gravity. The spacetime contains a non-extremal outer horizon and exhibits two notable features. Firstly, in the large-mass regime with $r_+=2M$, the Kretschmann scalar becomes nearly independent of the ADM mass and is mainly controlled by the inner horizon radius $r_-$, so that the curvature of spacetime remains sub-Planckian everywhere by choosing $r_-$ appropriately. Secondly, the near inner horizon amplification is softened from exponential to power-law behavior. In particular, within the double-null shell and Ori models, the internal Misner-Sharp mass remains finite at late times and approaches $r_-/2$.

gr-qc↗

arXiv2025

The stochastic gravitational wave background from QCD phase transition in the framework of higher-order GUP

This work studies the impact of a new higher-order generalized uncertainty principle (GUP) on the stochastic gravitational wave background (SGWB) associated with a QCD-scale first-order phase transition. Assuming a strongly first-order transition at the QCD-scale as a phenomenological benchmark, the analysis shows that the sign and magnitude of the dimensionless deformation parameter $β_0$ play a crucial role. For negative $β_0$, the thermodynamic quantities of the radiation fluid develop a maximal temperature beyond which entropy and pressure vanish, and the SGWB spectrum exhibits divergent behavior at high temperatures, so this branch is discarded as phenomenologically inconsistent. For positive $β_0$, the higher-order GUP shifts the SGWB peak frequency towards lower values and slightly enhances the peak energy density, with the size of the effect controlled by $β_0$. For natural values $β_0=\mathcal{O}\left( 1 \right)$ the corrections at QCD temperatures are strongly suppressed, whereas larger benchmark values still compatible with existing experimental and cosmological bounds can induce appreciable shifts in the SGWB spectrum. A future detection of a QCD-scale first-order SGWB would therefore allow the framework developed here to be used to translate the measured signal into constraints on the higher-order GUP parameter, providing an indirect probe of quantum gravity effects.

gr-qc↗

arXiv2025

Thermodynamics of the arbitrary dimensional FRW universe: Joule-Thomson expansion

In this paper, we investigate the thermodynamics especially the Joule-Thomson expansion of the $n$-dimensional FRW (Friedmann-Robertson-Walker) universe with a perfect fluid. We derive the thermodynamic equations of state $P=P(V, T)$ for the $n$-dimensional FRW universe in Einstein gravity and Einstein-Gauss-Bonnet gravity, where the thermodynamic pressure $P$ is defined by the work density $W$ of the perfect fluid, $i.e.$ $P\equiv W$. Furthermore, we present the Joule-Thomson expansion as an application of these equations of state to elucidate the cooling-heating properties of the $n$-dimensional FRW universe. We determine the inversion temperature and inversion pressure in the FRW universe with arbitrary dimensions for the first time, and illustrate the characteristics of inversion curves and isenthalpic curves in the $T$-$P$ plane. We also examine constraints on the perfect fluid in the FRW universe, as derived from the cooling-heating transition point. This study offers insights into deepening our comprehension of cooling and heating regions in the FRW universe, thereby revealing its expansion mechanisms.

gr-qc↗

arXiv2025

Spherical photon orbits around the Kerr-like black hole in Einstein-Bumblebee gravity

In this paper, we investigate the photon orbits around a Kerr-like black hole in Einstein-Bumblebee gravity, where Lorentz symmetry is spontaneously broken. By solving the Hamilton-Jacobi equation, we derive a sixth-order polynomial that governs the photon motion, explicitly dependent on the rotation parameter $u$, the Lorentz violation parameter $\ell$, and the effective inclination angle $v$. We analyze photon orbit configurations in polar, equatorial, and general inclined planes, identifying significant deviations from the Kerr solution. In the polar and equatorial planes, we identify distinct photon orbit configurations and analyze their dependence on model parameters. For general inclined orbits, we find a critical inclination angle $v$ that determines the number and location of photon orbits in both extremal and non-extremal cases. All photon orbits are radially unstable, and the critical impact parameter decreases with increasing Lorentz violation, potentially providing observable signatures to differentiate Einstein-Bumblebee gravity from general relativity.

gr-qc↗

arXiv2025

Symmetric black-to-white hole solutions with a cosmological constant

For a system with a Hamiltonian constraint, we demonstrate that its dynamics is invariant under different choices of the lapse function, regardless of whether the Hamiltonian incorporates quantum corrections. Applying this observation to the interior of black-to-white holes, we analyze its dynamics with different choices of the lapse function. The results explicitly show that the leading-order expansion of both metrics proposed by Rovelli et al. (Class. Quant. Grav. \textbf{35}, 225003 (2018); Class. Quant. Grav. \textbf{35}, 215010 (2018)) and Ashtekar et al. (Phys. Rev. Lett. \textbf{121}, 241301 (2018); Phys. Rev. D \textbf{98}, 126003 (2018)) exhibit identical behavior near the transition surface. Therefore, in this sense the black-to-white hole model proposed by Rovelli et al., (Class. Quant. Grav. \textbf{35}, 225003 (2018); Class. Quant. Grav. \textbf{35}, 215010 (2018)) may be interpreted as a coarse-grained version of the solution within the framework of loop quantum gravity. The black-to-white hole solutions with exact symmetry between the black hole and white hole regions are constructed by appropriately fixing the quantum parameters in the effective theory of loop quantum gravity. This approach circumvents the issue of amplification of mass, which could arise from a mass difference between the black hole and white hole, and provides a way to link the solutions obtained by minisuperspace quantization to those in the covariant approach. Finally, the black-to-white hole solutions with a cosmological constant are constructed. The numerical solutions for the interior of the black-to-white hole with a cosmological constant are obtained, and their symmetric behavior is also discussed.

gr-qc↗

arXiv2024

Spherical photon orbits around Kerr-MOG black hole

This study investigates photon orbits around Kerr-MOG black holes. The equation of photon of motion around the Kerr-MOG black hole is derived by solving the Hamilton-Jacobi equation, expressed as a sixth-order polynomial involving the inclination angle $v$, the rotation parameter $u$, and the deformation parameter $α$ that characterizes modified gravity. We find that $α$ constrains the rotation of the black hole, modifying its gravitational field and leading to distinct photon orbital characteristics. Numerical analysis reveals that the polar plane ($v=1$) has two effective orbits: one outside and one inside the event horizon, while the equatorial plane ($v=0$) has four effective orbits: two outside and two inside the event horizon. Moreover, we derive the exact formula for general photon orbits between the polar and equatorial planes ($0<v<1$). In the extremal case, the rotation speed significantly impacts general photon orbits. A slowly rotating extremal black hole has two general photon orbits outside the event horizon, whereas a rapidly rotating extremal black hole has only one such orbit. In the non-extremal case, a critical inclination angle $v_{cr}$ exists in the parameter space $\left(v, u, α\right)$. Below $v_{cr}$, there are four general photon orbits, while above $v_{cr}$, there are two orbits. At the critical inclination angle, three solutions are found: two photon orbits outside and one inside the event horizon. Additionally, the results indicate that all orbits are radially unstable. Furthermore, by analyzing photon impact parameter, we argue that $α$ influences observational properties of the black hole.

gr-qc↗

arXiv2024

The new higher-order generalized uncertainty principle and primordial big bang nucleosynthesis

As an important class of quantum gravity models, the generalized uncertainty principle (GUP) plays an important role in exploring the properties of cosmology and its related problems. In this paper, we explore the influence of the higher-order GUP on the primordial big bang nucleosynthesis (BBN). Firstly, based on a new higher-order GUP, we derived the Friedmann equations influenced by quantum gravity and the corresponding thermodynamic properties of the universe. Then, according to these modifications, we investigate BBN within the framework of GUP. Finally, combining the observational bounds of the primordial light element abundances, we constrain the bounds on deformation parameters of the new higher-order GUP. The results show that GUP has a significant effect on the BBN of the universe. Moreover, due to the unique properties of the higher-order GUP, it is found that value of the deformation parameter can be both positive and negative, which is different from the classical case.

gr-qc↗

arXiv2024

Phase transitions, critical behavior and microstructure of the FRW universe in the framework of higher order GUP

In this paper, we explore the the phase transition, critical behavior and microstructure of the FRW in the framework of a new higher order generalized uncertainty principle. Our initial step involves deriving the equation of state by defining the work density $W$ from GUP-corrected Friedmann equations as the thermodynamic pressure $P$. Based on the modified equation of state, we conduct an analysis of the $P-V$ phase transition in the FRW universe. Subsequently, we obtain the critical exponents and coexistence curves for the small and large phases of the FRW universe around the critical point. Finally, employing Ruppeiner geometry, we derive the thermodynamic curvature scalar $R_N$, investigating its sign-changing curve and spinodal curve. The results reveal distinctive thermodynamic properties for FRW universes with positive and negative GUP parameters $β$. In the case of $β>0$, the phase transition, critical behavior and microstructure of FRW universe are consistent with those of Van der Waals fluids. Conversely, for $β<0$, the results resemble those obtained through effective scalar field theory. These findings underscore the capacity of quantum gravity to induce phase transitions in the universe, warranting further in-depth exploration.

gr-qc↗

arXiv2024

New black-to-white hole solutions with improved geometry and energy conditions

We construct new black-to-white hole solutions which connect the geometry of spacetime at some gluing surface inside the horizon. The continuity of the metric can be guaranteed up to the arbitrary order which is controlled by the power factor $n$. This sort of black-to-white holes is characterized by the sub-Planckian scalar curvature, independent of the mass of black-to-white holes. More importantly, we show that the energy condition is only violated within a small region near the gluing surface. The geodesics of particles within the region from black hole to white hole is also analyzed. It turns out that the matter falling into the black hole may pass through the center without singularity and come out from the white hole. This scenario provides novel ideas for understanding the information loss paradox in traditional black hole physics.

gr-qc↗

arXiv2023

The gravitational baryogenesis and a new higher-order extended uncertainty principle with parameter adaptability for the minimum length

In this manuscript, we explore the baryon asymmetry of the universe by employing a novel higher-order extended uncertainty principle (EUP) that maintains a minimum length ${\rm{Δ}}{x_{\rm min}} =4\sqrt {\left| {\rm{β_0 }} \right|}\ell _p $ for both positive and negative deformation parameters. Our results demonstrate that the influence of the EUP noticeably modifies the Friedmann equations, leading to a transformation in the characteristics of the pressure and density of the Universe, and subsequently disrupting its thermal equilibrium. Additionally, by amalgamating the adapted Friedmann equations with the conventional theory of gravitational baryogenesis, one can derive a non-zero factor of baryon asymmetry $η$, indicating that the quantity of matter in the universe surpasses that of antimatter. Finally, we also utilized astronomical observations to constrain the bounds for both the positive and negative deformation parameters.

gr-qc↗

arXiv2023

Barrow entropy and stochastic gravitational wave background generated from cosmological QCD phase transition

In this work we investigate the stochastic gravitational wave background generated during the f\/irst-order cosmological QCD phase transition of the early universe in the framework of the Barrow entropy. We f\/irst derived the Barrow corrections to the expression of stochastic gravitational wave background spectrum in presence of trace anomaly. Then, by taking account of Bubble wall collisions, sound waves and magnetohydrodynamic turbulence as the sources of stochastic gravitational wave, an analysis of the influence of Barrow entropy on the total energy density and the peak signal of stochastic gravitational wave signal is carried out. Finally, we discuss the possibility of detectors for the detection of these stochastic gravitational wave signals. Our results show that effect of Barrow entropy plays an important role in the temporal evolution of temperature of the universe as a function of the Hubble parameter, which leads to the signal of stochastic gravitational wave to shift towards the lower frequency regime, making the signal of stochastic gravitational wave possible to be probed by relevant ongoing and upcoming gravitational waves experiments.

gr-qc↗

arXiv2022

Higher-order generalized uncertainty principle applied to gravitational baryogenesis

The gravitational baryogenesis plays an important role in the study of the baryon asymmetry. However, the original mechanism of gravitational baryogenesis in the radiation dominated era leads to the asymmetry factor $η$ is equal to zero, which indicates this mechanism may not generate a sufficient baryon asymmetry for the standard cosmological model. In this manuscript, we investigate the gravitational baryogenesis for the generation of baryon asymmetry in the early Universe by using an new higher-order generalized uncertainty principle (GUP). It is demonstrated that the entropy and Friedman equation of the Universe deviate from the original cases due to the effect of the higher-order GUP. Those modifications break the thermal equilibrium of the Universe and in turn produces a non-zero asymmetry factor $η$. In particular, our results satisfy all three Sakharov conditions, which indicates that the scheme of explaining baryon asymmetry in the framework of higher-order GUP is feasible. In addition, confronting our theoretical results with the observational results, we constraint the GUP parameter $β_0$, whose bound between $8.4 \times {10^{10}} \sim 1.1 \times {10^{13}}$.

gr-qc↗

arXiv2022

Quantum corrections to the thermodynamics and phase transition of a black hole surrounded by a cavity in the extended phase space

In the extended phase space, we investigate the rainbow gravity-corrected thermodynamic phenomena and phase structure of the Schwarzschild black hole surrounded by a spherical cavity. The results show that rainbow gravity has a very significant effect on the thermodynamic phenomena and phase structure of the black hole. It prevents the black hole from total evaporation and leads to a remnant with a limited temperature but no mass. Additionally, we restore the $P-V$ criticality and obtaine the critical quantities of the canonical ensemble. When the temperature or pressure is smaller than the critical quantities, the system undergoes two Hawking-Page-like phase transitions and one first-order phase transition, which never occurs in the original case. Remarkably, our findings demonstrate that the thermodynamic behavior and phase transition of the rainbow SC black hole surrounded by a cavity in the extended phase space are analogous to those of the Reissner-Nordström anti-de Sitter black hole. Therefore, rainbow gravity activates the effect of electric charge and cutoff factor in the evolution of the black hole.

gr-qc↗

arXiv2022

The generalized uncertainty principle impact onto the black hole thermodynamic phase transition

In this work, we conduct a study regarding the thermodynamic evolution and the phase transition of a black hole in a finite spherical cavity subject to the generalized uncertainty principle. The results demonstrate that both the positive and negative generalized uncertainty principle parameters $β_0$ can significantly affect the thermodynamic quantities, stability, critical behavior, and phase transition of the black hole. For $β_0>0$, the black hole forms a remnant with finite temperature, finite mass, and zero local heat capacity in the last stages of evolution, which can be regarded as an elementary particle. Meanwhile, it undergoes one second-order phase transition and two Hawking-Page-type phase transitions. The Gross-Perry-Yaffe phase transition occurs for both large black hole configuration and small black hole configuration. For $β_0<0$, the Gross-Perry-Yaffe phase transition occurs only for large black hole configuration, and the temperature and heat capacity of black hole remnant is finite, whereas its mass is zero. This indicates the remnant is metastable and would be in the Hawking-Page-type phase transition forever. Specifically, according to the viewpoint of corpuscular gravity, the remnant can be interpreted as an additional metastable tiny black hole configuration, which never appears in the original case and the positive correction case.

gr-qc↗

arXiv2021

Higher-order generalized uncertainty principle corrections to the Jeans mass

The Jeans instability is regarded as an important tool for analyzing the dynamics of a self-gravitating system. However, this theory is challenging since astronomical observation data show some Bok globules, whose masses are less than the Jeans mass and still have stars or at least undergo the star formation process. To explain this problem, we investigate the effects of the higher-order generalized uncertainty principle on the Jeans mass of the collapsing molecular cloud. The results in this paper show that the higher order generalized uncertainty principle has a very significant effect on the canonical energy and gravitational potential of idea gas, and finally leads to a modified Jeans mass lower than the original case, which is conducive to the generation of stars in small mass Bok globules. Furthermore, we estimate the new generalized uncertainty principle parameter $γ_0$ by applying various data of Bok globules, and find that the range of magnitude of $γ_0$ is ${10^{11}} \sim {10^{12}}$.

physics.gen-ph↗

arXiv2021

Joule-Thomson expansion of higher dimensional nonlinearly charged AdS black hole in Einstein-PMI gravity

In this paper, the Joule-Thomson expansion of the higher dimensional nonlinearly AdS black hole with power Maxwell invariant source is investigated. The results show the Joule-Thomson coefficient has a zero point and a divergent point, which are coincide with the inversion temperature $T_i$ and the zero point of Hawking temperature, respectively. The inversion temperature increases monotonously with inversion pressure. For high-pressure region, the inversion temperature decreases with the dimensionality $D$ and the nonlinearity parameter $s$, whereas it increases with the charge $Q$. However, $T_i$ for low-pressure region increase with $D$ and $s$, while it decreases with $Q$. The ratio ${η_{\rm{BH}}}$ between the minimum of inversion temperature and the critical temperature does not depend on $Q$, it recovers the higher dimensional Reissner-Nördstrom AdS black hole case when $s=1$. However, for $s>1$, it becomes smaller and smaller as $D$ increase and approaches a constant when $D\rightarrow\infty$. Finally, we found that increase of mass $M$ and $s$, or reduce the charge $Q$ and $D$ can enhance the isenthalpic curve, and the effect of $s$ on the isenthalpic curve is much greater than other parameters.

gr-qc↗