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Gravitational wave fluxes on generic orbits in near-extreme Kerr spacetime:Higher spin and large eccentricity

Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 16-28页

作者： Changkai Chen Jiliang Jing Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

To accurately obtain the waveform template of gravitational waves, substantial computational resources and extremely high precision are often required. In a previous study, we employed the confluent Heun function to obtain an exact solution to the Teukolsky equation. This approach allowed us to efficiently and accurately calculate the gravitational wave flux for a particle in circular orbits around a Schwarzschild black hole. Building on this method, we now extend its application to calculate the asymptotic gravitational wave fluxes from a particle in generic orbits around a near-extreme Kerr black hole. Our extended method proves particularly effective in handling computational challenges associated with large eccentricities(e = 0.9), higher spins(a = 0.999), higher harmonic modes, and strong-field regions. The results we obtained significantly outperform those derived from the numerical integration method based on the Mano-Suzuki-Takasugi method.

关键词： gravitational wave fluxes exact solution Teukolsky equation near-extreme Kerr black hole

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Thermodynamics of charged AdS black hole surrounded by quintessence in restricted phase space

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Chinese Physics B 2024年第10期33卷 205-212页

作者： Siyu Jian Siying Long Juhua Chen Yongjiu Wang Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Educationand Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

We study thermodynamics of charged AdS black hole surrounded by quintessence in a new formalism which is called the restricted phase space *** context is based on Visser’s holographic thermodynamics with a fixed antide Sitter radius and a variable Newton *** conjugate variables,central charge C and the chemical potential m,are introduced as a new pair of thermodynamic *** find that the iso-e-charge T-S curve becomes non-monotonic when Qlow tail *** behavior is considered as a van der Waals-like phase *** the value of b related to the energy density of Kiselev’s fluid becomes larger,the critical temperature T_(c)will ***,the van derWaals-like phase transition will occur at lower *** is always a non-quilibrium transition from a small unstable black hole to a large stable black hole state in the isocoltage T-S *** exist a maximum and a Hawking-Page phase transition points in theμ-C *** the value of b related to Kiselev’s fluid becomes larger,the Hawking-Page phase transition will occur at lower temperature in the isovoltageμ-T *** other values of the state parameterω,there also exists van der Waals-like phase transition.

关键词： Reissner-Nordstrom qAdS black hole restricted phase space variable Newton constant

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Lorentz violation induces isospectrality breaking in Einstein-bumblebee gravity theory

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Science China(Physics,Mechanics & Astronomy) 2024年第8期67卷 87-96页

作者： Wentao Liu Xiongjun Fang Jiliang Jing Jieci Wang Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

In this study,we investigate the quasinormal modes(QNMs)of a Lorentz-violating spacetime,factoring in a cosmological constant,within the framework of Einstein-bumblebee *** findings reveal that the interaction of spacetime with an anisotropic bumblebee field imparts distinct contributions to the axial and polar sectors of the vector *** subsequently breaks the isospectrality typically observed in vector *** evidence strongly indicates isospectral breaking in the vector modes of Einstein-bumblebee black holes:a pronounced breakage in the real part of the frequencies,while the imaginary component seems less *** isospectral breaking indicates the existence of two different waveforms in the Ringdown phase of the black hole,which provides a potential signal of quantum gravity observable in current experiments.

关键词： Lorentz-violating isospectral breaking quasinormal modes

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Possibility of synthesizing Z=119 superheavy nuclei with Z>20 projectiles

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Chinese Physics C 2024年第12期48卷 151-157页

作者： Hao Zhu Tian-Liang Zhao Xiao Jun Bao Department of Physics Collaborative Innovation Center for Quantum Effectsand Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationHunan Normal UniversityChangsha 410081China

We employ the dinuclear system(DNS)model combined with a statistical model to calculate the evaporation residue cross sections of the reaction systems ^(48)Ca+^(243)Am,^(48)Ca+^(248)Cm,and ^(48)Ca+^(249)*** theoretical results successfully reproduce the experimental trends in the 3n and 4n evaporation channels of these reaction *** synthesize the new element,we predict the evaporation residue cross sections for three reaction systems(^(54)Cr+^(243)Am,^(51)V+^(248)Cm,and ^(50)Ti+^(249)Bk)to select the most promising projectile-target *** also note that the maximum cross sections predicted by our model and other methods appear to be below the detection limits of current experimental facilities,given the projectile-target combinations feasible under current experimental ***,synthesizing superheavy nuclei with Z=119 will require improvements in beam intensity,detection techniques,and effective separation methods.

关键词： superheavy nuclei evaporation residue cross sections dinuclear system model

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Efficient CORDIC-Based Activation Functions for RNN Acceleration on FPGAs

IEEE Transactions on Artificial Intelligence

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IEEE Transactions on Artificial Intelligence 2025年第1期6卷 199-210页

作者： Shen, Wan Jiang, Junye Li, Minghan Liu, Shuanglong Hunan Normal University Key Laboratory of Low-Dimensional Quantum Structures Quantum Control of Ministry of Education School of Physics and Electronics Changsha410081 China

Recurrent neural networks (RNNs), particularly long short-term memory (LSTM) networks, have emerged as standard tools for tackling a wide range of time series applications, such as natural language processing. However, deploying these models on edge devices presents great challenges due to limited computational resources. Additionally, the implementation of RNN activation functions on low-end hardware devices significantly impacts the overall network performance, as activations constitute the dominant part of execution time. In this work, we propose an efficient approach for implementing commonly used RNN activations, leveraging an optimized coordinate rotation digital computer algorithm (CORDIC). Moreover, we propose a unified hardware architecture for mapping the CORDIC-based method onto field-programmable gate arrays (FPGAs), which can be configured to implement multiple nonlinear activation functions. Our architecture reduces the computational time with fewer iterations in CORDIC compared with existing methods, rendering it particularly suitable for resource-constrained edge devices. Our design is implemented on a Xilinx Zynq-7000 device and evaluated across three RNNs and benchmark datasets. Experimental results demonstrate that our design achieves up to a 2× speedup while maintaining model accuracy compared with the state-of-the-art designs. © 2024 IEEE.

关键词： Long short-term memory

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quantum phase transition of the Jaynes-Cummings model

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 1-9页

作者： Cheng Liu Jin-Feng Huang Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan ProvinceDepartment of Physics and Synergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesHunan Normal UniversityChangsha 410081China

Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong *** tuning the modulation frequency and amplitude,the ratio of the effective coupling strength of the rotating terms to the effective cavity(atomic transition)frequency can enter the deep-strong coupling regime,while the counter-rotating terms can be ***,a deep-strong JC model is *** ratio of the coupling strength to resonance frequencies in the deep-strong JC model is two orders of magnitude larger than the corresponding ratio in the original quantum Rabi *** scheme can be employed in atom-cavity resonance and off-resonance cases,and it is valid over a broad *** nonzero average cavity photons of the ground state indicate the emergence of a quantum phase ***,we demonstrate the dependence of the phase diagram on the atom-cavity detuning and modulation *** the parameters used in our scheme are within the reach of current experimental *** scheme provides a new mechanism for investigating the critical phenomena of finite-sized systems without requiring classical field limits,thereby opening a door for studying fundamental quantum phenomena occurring in the ultrastrong and even deep-strong coupling regimes.

关键词： Jaynes-Cummings model quantum phase transition frequency modulation

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Spontaneous emission of a moving atom in a waveguide of rectangular cross section

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Chinese Physics B 2023年第2期32卷 92-96页

作者：曾静卢竞周兰 Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics and Synergetic Innovation Center of Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

We study the spontaneous emission(SE) of an excited nonrelativistic two-level system(TLS) interacting with the vacuum in a waveguide of rectangular cross section. All TLS’s transitions and the center-of-mass motion of the TLS are taken into account. The SE rate and the carried frequency of the emitted photon for the TLS initially being at rest are obtained, it is found that in the first order of the mass M, the frequency of the emitted photon is smaller than the transition frequency of the TLS and the SE rate is smaller than the SE rate Γfof the TLS fixed in the same waveguide. The SE rate for the TLS initially being moving is obtained in the second order of the mass M. The SE rate is smaller than Γfbut it is dependent not only on the atomic mass but also on the initial momentum. The carried frequency of the emitted photon is decreased when it travels along the direction of the initial momentum, whereas it is increased when it travels in the opposite direction of the initial momentum.

关键词： spontaneous emission moving atom waveguide of rectangular cross section

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Anti-parity-time symmetry hidden in a damping linear resonator

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Science China(Physics,Mechanics & Astronomy) 2023年第10期66卷 22-32页

作者： Xun-Wei Xu Jie-Qiao Liao Hui Jing Le-Man Kuang Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan ProvinceDepartment of Physics and Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China

Phase transition from the over-damping to under-damping states is a ubiquitous phenomenon in physical systems. However, what kind of symmetry is broken associated with this phase transition remains unclear. Here, we discover that this phase transition is determined by an anti-parity-time(anti-PT) symmetry hidden in a single damping linear resonator, which is significantly different from the conventional anti-PT-symmetric systems with two or more modes. We show that the breaking of the anti-PT symmetry yields the phase transition from the over-damping to under-damping states, with an exceptional point(EP) corresponding to the critical-damping state. Moreover, we propose an optomechanical scheme to show this anti-PT symmetry breaking by using the optical spring effect in a quadratic optomechanical system. We also suggest an optomechanical sensor with the sensitivity enhanced significantly around the EPs for the anti-PT symmetry breaking. Our work unveils the anti-PT symmetry hidden in damping oscillations and hence opens up new possibilities for exploiting wide anti-PT symmetry applications in single damping linear resonators.

关键词： anti-parity-time symmetry exceptional points damping linear resonator optomechanics

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Energy flux and waveforms by coalescing spinless binary system in effective one-body theory

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Science China(Physics,Mechanics & Astronomy) 2024年第6期67卷 58-68页

作者： Sheng Long Weike Deng Jiliang Jing Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We present a study on the energy radiation rate and waveforms of the gravitational wave generated by coalescing spinless binary systems up to the third post-Minkowskian approximation in the effective one-body *** derive an analytical expansion of the null tetrad components of the gravitational perturbed Weyl tensorΨ4in the effective spacetime,we utilize the method proposed by Sasaki et *** this investigation,we discover more general integral formulas that provide a theoretical framework for computing the results in any ***,we successfully compute the energy radiation rate and waveforms of the gravitational wave,which include the results of the Schwarzschild case and the correction terms resulting from the dimensionless parameters a2and a3in the effective metric.

关键词： post-Minkowskian approximation effective one-body theory gravitational waveform template

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Energy flux and waveform of gravitational wave generated by coalescing slow-spinning binary system in effective one-body theory

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Science China(Physics,Mechanics & Astronomy) 2024年第9期67卷 73-83页

作者： Weike Deng Sheng Long Jiliang Jing Department of Physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Educationand Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We extend our research on the energy flux and waveform characteristics of gravitational waves generated by merging nonspinning binary black holes through self-consistent effective one-body theory to include binary systems with slowly spinning black ***,we decompose the equation for the null tetrad component of the gravitationally perturbed Weyl tensorψ_4~B into radial and angular parts,leveraging the second-order approximation of the rotation parameter ***,we derive an analytical solution for the radial equation and observe that our results are contingent upon the parameters a_(2),a_(3),and a,which represent the second-and third-order correction parameters,***,we calculate the energy flux,the radiation-reaction force and the waveform for the“plus”and“cross”modes of the gravitational waves generated by merging slowly spinning binary black holes.

关键词： post-Minkowskian approximation effective-one-body theory gravitational waveform template

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