Zhuan Ning

Zhuan Ning

A PhD candidate at the Institute of Theoretical Physics, Chinese Academy of Sciences

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publications

Descalarization by quenching charged hairy black hole in asymptotically AdS spacetime

Published in JHEP, 2023

Abstract: In this work, we study the real-time dynamics of the charged hairy black hole with the time-dependent source of scalar field in asymptotically anti-de Sitter (AdS) spacetime. The numerical results reveal a novel descalarization mechanism. In order to obtain the hairy black hole as the initial data for the quench process, we first analyze the quasi-normal modes of the massive complex scalar field on the Reissner-Nordström anti-de Sitter (RN-AdS) black hole background. We find the dominant unstable modes for large and small RN-AdS black holes come from the zero-damped modes and AdS modes, respectively. Then, the unstable RN-AdS black holes are perturbed to trigger the transition to hairy black holes. With the hairy black hole in hand, we specify a time dependent scalar source for the system. As the source is turned on, the electric charge, energy and scalar condensation of the system start to oscillate with the entropy increasing monotonically. Finally, with the decay of the scalar source, the system gradually settles down to a new state. Interestingly, the final state of the evolution could be a hairy black hole with less scalar condensation, a RN-AdS black hole or a Schwarzschild-AdS black hole, which depends on the quench strength. However, as long as the quench strength is large enough, the system always loses all the electric charge and converges to the Schwarzschild-AdS black hole.

Recommended citation: Q.~Chen, Z.~Ning, Y.~Tian, B.~Wang and C.~Y.~Zhang, ``Descalarization by quenching charged hairy black hole in asymptotically AdS spacetime,'' JHEP \textbf{01}, 062 (2023), [arXiv:2210.14539 [hep-th]].
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Nonlinear dynamics of hot, cold, and bald Einstein-Maxwell-scalar black holes in AdS spacetime

Published in Phys.Rev.D, 2023

Abstract: We investigate the dynamical transition processes of an Einstein-Maxwell-scalar gravitational system between two local ground states and an excited state in the anti–de Sitter spacetime. From the linear perturbation theory, only the excited state possesses a single unstable mode, indicating the dynamical instability. Such an instability is associated with the tachyonic instability due to the presence of an effective potential well near the event horizon. From the nonlinear dynamics simulation, through the scalar field accretion mechanism, the critical phenomena in the transition process of the gravitational system between the two local ground states are revealed. The threshold of the accretion strength indicates the existence of a dynamical barrier in this transition process, which depends on the coupling strength between the scalar and Maxwell fields. On the other hand, for the unstable excited state, there exists a special kind of critical dynamics with a zero threshold for the perturbation strength. The perturbations of different signs push the gravitational system to fall into different local ground states. Interestingly, in an extended parameter space, there exist specific parameters such that the perturbations of nonzero amplitude fail to trigger the single unstable mode of the excited state.

Recommended citation: Q.~Chen, Z.~Ning, Y.~Tian, B.~Wang and C.~Y.~Zhang, ``Nonlinear dynamics of hot, cold and bald Einstein-Maxwell-scalar black holes in AdS spacetime,'' Phys. Rev. D \textbf{108}, 084016 (2023), [arXiv:2307.03060 [gr-qc]].
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Time evolution of Einstein-Maxwell-scalar black holes after a thermal quench

Published in JHEP, 2023

Abstract: We employ the holographic quench technique to drive Einstein-Maxwell-scalar (EMs) black holes out of equilibrium and study the real-time dynamics therein. From the fully nonlinear dynamical simulations, a dynamically unstable Reissner-Nordström anti-de Sitter (RN-AdS) black hole can be scalarized spontaneously after an arbitrarily small quench. On the other hand, a dynamically stable scalarized black hole can be descalarized after a quench of sufficient strength. Interestingly, on the way to descalarization, the scalarized black hole behaves like a holographic superfluid, undergoing a dynamical transition from oscillatory to non-oscillatory decay. Such behaviors are related to the spectrums of quasi-normal modes of scalarized black holes, where the dominant mode migrates toward the imaginary axis with increasing quench strength. In addition, due to the $\mathbb{Z}_{2}$-symmetry preserved by the model, the ground state is degenerate. We find that there exists a threshold for the quench strength that induces a dynamical transition of the gravitational system from one degenerate ground state to the other. Near the threshold, the gravitational system is attracted to an excited state, that is, a RN-AdS black hole with dynamical instability.

Recommended citation: Q.~Chen, Z.~Ning, Y.~Tian, X.~Wu, C.~Y.~Zhang and H.~Zhang, ``Time evolution of Einstein-Maxwell-scalar black holes after a thermal quench,'' JHEP \textbf{10}, 176 (2023), [arXiv:2308.07666 [gr-qc]].
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Spontaneous deformation of an AdS spherical black hole

Published in Phys.Rev.D, 2024

Abstract: In this study, we investigate the real-time dynamics during the spontaneous deformation of an unstable spherical black hole in asymptotically anti–de Sitter (AdS) spacetime. For the initial value, the static solutions with spherical symmetry are obtained numerically, revealing the presence of a spinodal region in the phase diagram. From the linear stability analysis, we find that only the central part of such a thermodynamically unstable spinodal region leads to the emergence of a type of axial instability. To trigger the dynamical instability, an axial perturbation is imposed on the scalar field. As a result, by the fully nonlinear dynamical simulation, the spherical symmetry of the gravitational system is broken spontaneously, leading to the formation of an axisymmetric black hole.

Recommended citation: Z.~Ning, Q.~Chen, Y.~Tian, X.~Wu and H.~Zhang, ``Spontaneous deformation of an AdS spherical black hole,'' Phys. Rev. D \textbf{109}, 064082 (2024), [arXiv:2307.14156 [gr-qc]].
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talks

teaching

General Relativity

Graduate Course-Teaching Assistant, University of Chinese Academy of Sciences, School of Physical Sciences, 2022

Lie Group and Lie Algebra

Graduate Course-Teaching Assistant, University of Chinese Academy of Sciences, School of Physical Sciences, 2023

General Relativity

Graduate Course-Teaching Assistant, University of Chinese Academy of Sciences, School of Physical Sciences, 2023