arXiv subjects

Li-Gang Zhu

Publications and source records attributed to Li-Gang Zhu.

4 recordsLinked to original sources

arXiv2025

Probing loop quantum effects through solar system experiments: observational signatures and parameter constraints

This study investigates quantum gravity effects within the framework of an effective loop quantum gravity (LQG) black hole model parameterized by $\zeta$, utilizing precision measurements from solar system experiments and astrophysical observations. We analyze three classical tests of general relativity (GR): (1) Light deflection constrained by very long baseline interferometry (VLBI) observations of quasar radio signals, (2) Shapiro time delay measurements from the Cassini mission, and (3) Mercury's perihelion precession determined by MESSENGER mission data. Additionally, we extend our analysis to Earth-orbiting LAGEOS satellites and the relativistic trajectory of the S2 star orbiting the Galactic Center supermassive black hole Sagittarius $\rm{A}^*$ (Sgr $\rm{A}^{*}$). Our multi-probe approach reveals that the tightest constraint on the LQG parameter comes from Mercury's perihelion precession, yielding an upper bound $\zeta \lesssim 10^{-2}$. These results establish new observational benchmarks for probing quantum gravity effects.

gr-qc↗

arXiv2024

Quasinormal modes of a charged loop quantum black hole

This study presents a systematic investigation of quasinormal modes (QNMs) for probe fields-massless/massive scalar and Dirac fields-around a charged loop quantum gravity black hole (LQG-BH) characterized by the quantum parameter $b_0$ and the charge parameter $Q$. Through spectral analysis of quasinormal frequencies (QNFs), we uncover a distinct overtone outburst driven by quantum gravity effects, prominently manifested in the scalar field spectrum with the multipole quantum number $l=0$. Both the outburst and its accompanying oscillatory patterns grow more pronounced with increasing overtone numbers. In contrast, massless scalar fields with $l>1$ and Dirac fields exhibit delayed outburst development, with non-monotonic behavior dominating the first two overtones. Notably, increasing the charge $Q$ universally suppresses quantum-gravity-induced features, including outbursts, non-monotonicity, and oscillations. Furthermore, we present evidence suggesting the presence of quasi-resonances in the massive scalar QNM spectrum, thereby illustrating the potential for the emergence of arbitrarily long-lived modes in this charged LQG spacetime. These findings establish a robust and universal interplay between quantum gravity effects and charge dynamics, providing new insights into the spectral properties of quantum-corrected BHs.

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arXiv2024

Quasinormal modes and ringdown waveform of the Frolov black hole

In this paper we investigate scalar perturbation over a Frolov black hole (BH), which is a regular BH induced by the quantum gravity effect. The quasinormal frequencies of a scalar field always consistently reside in the lower half-plane, and the time-domain evolution of the field demonstrates a decaying behavior, with the late-time tail exhibiting a power-law pattern. These observations collectively suggest the stability of a Frolov BH against scalar perturbation. Additionally, our study reveals that the quantum gravity effect leads to slower decay modes. For the case of the angular quantum number $l=0$, the oscillation exhibits non-monotonic behavior with the quantum gravity parameter $\alpha_0$. However, once $l\geq 1$, the angular quantum number surpasses the influence of the quantum gravity effect.

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arXiv2023

Constraints from Solar System tests on a covariant loop quantum black hole

Recently, a covariant spherically symmetric model of a black hole within the framework of loop quantum gravity (LQG), characterized by a quantum parameter $r_0$ or $\lambda$, has been proposed. To derive constraints on the LQG-corrected parameter, we explore observational constraints imposed on $r_0$ and $\lambda$ through investigations of the light deflection, the Shapiro time delay, the precession of perihelia, and the geodetic precession test. Among these constraints, the tightest one arises from the Shapiro time delay measured by the Cassini mission, yielding an upper constraint of approximately $10^{-5}$.

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