Xiangdong Zhang

In this paper, we investigate the dynamics and gravitational-wave signatures of periodic orbits of spinning test particles moving in the equatorial plane around static, spherically symmetric black holes within the framework of Deser-Woodard nonlocal gravity. Based on the Mathisson-Papapetrou-Dixon equations, combined with the Tulczyjew spin supplementary condition, we derive the orbital dynamic equations for spinning particles moving in the equatorial plane and impose a timelike constraint to exclude unphysical superluminal trajectories. By comparing with the classical Schwarzschild black hole, we systematically analyze the effects of the nonlocal gravitational parameters ζ and b on the effective potential governing the radial motion of particles and the innermost stable circular orbit. In addition, gravitational waveforms exhibit significant phase differences: an increase in ζ induces a phase delay, whereas an increase in b results in a phase advance. A oneyear simulation of the orbital evolution of an extreme mass ratio inspiral demonstrates that when b = 2 and ζ ≈ 10 -6 , the mismatch between the gravitational waveforms predicted for the nonlocal gravity black hole and those for the Schwarzschild black hole reaches the distinguishable threshold (M = 0.0125), providing a basis for observational discrimination between general relativity and nonlocal gravity.

Unifying the early-universe inflationary paradigm with late-time cosmic acceleration, while resolving the initial Big Bang singularity, remains one of the most profound challenges in modern cosmology. In this paper, we propose a non-singular quintessential inflation model embedded within the effective dynamics of Loop Quantum Cosmology (LQC) based on a Generalized Regularization Scheme. The quantum geometry effects naturally replace the initial singularity with a quantum bounce, followed by a phase of superinflation that sets robust initial conditions for the subsequent slow-roll inflation. To achieve a viable late-time dark energy epoch and address the coincidence problem, we introduce a coupling between the scalar field and massive neutrinos, known as Mass-Varying Neutrinos(MaVaNs). As neutrinos become non-relativistic in the post-inflationary evolution, their backreaction effectively freezes the scalar field, triggering the late-time accelerated expansion. We numerically trace the full background dynamics from the quantum bounce to the present day. Furthermore, we tightly constrain the model parameters utilizing the observational data, including the Type Ia supernovae sample, the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB) distance priors. Our results demonstrate that this unified LQC-MaVaNs quintessential framework is highly consistent with current precision cosmological observations, and importantly, offers a viable methodology to observationally constrain the Barbero-Immirzi parameter.

We extended the higher-dimensional quantum Oppenheimer–Snyder model to the case with a cosmological constant. For the AdS case, we discuss its thermodynamic properties in extended phase space formalism and make a comparison with classical black holes. For quantum-corrected small black holes in AdS spacetime, the temperature no longer diverges but tends to zero. Additionally, the heat capacity exhibits characteristic behavior indicative of an extra phase transition induced by quantum corrections, highlighting the profound impact of quantum effects on black hole thermodynamics.

We investigate the gravitational lensing effects of a static spherically symmetric black hole (BH) within the framework of the revised Deser-Woodard (D-W) nonlocal gravity. By analyzing the deflection angle in both the weak and strong field limits, we derive several distinguishing features of the model. In the weak field limit, we report a leading-order correction to the deflection angle directly attributed to the non-local nature of the theory. In the strong field limit, we find that the lensing corrections are almost linearly dependent on the coupling parameter ζ while being exponentially suppressed by the exponent parameter n . Furthermore, the gravitational lensing effect in the revised D-W model at a given time shares similar scale-invariant behavior to General Relativity and conformal gravity, offering a potential pathway to distinguish it from other alternatives using astronomical observations.

In this work, we construct a new family of exact five-dimensional charged and rotating asymptotically Lifshitz black holes. The spacetime solves Einstein equations coupled to a dilaton, two Abelian gauge fields, and axionic scalars supplemented by two generalized Chern-Simons terms. This configuration is characterized by a range of the free dynamical exponent z and possesses nontrivial thermodynamical parameters, where we verify the first law of black hole thermodynamics and derive the corresponding Smarr relation. As an application of this new gravitational background, we then investigate a holographic superconductor in the rotating Lifshitz background. We study the condensation of the scalar operator and the AC conductivity of the dual system. These results show that increasing the rotation parameter suppresses the condensate and weakens the superconducting phase, while increasing the dynamical critical exponent enhances the superconducting order. To the best of our knowledge, these solutions provide the first explicit family of five-dimensional rotating Lifshitz black holes supported simultaneously by electric and axionic charges.