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  • Quantum Physics and Quantum Information
    Linshuai Zhang, Nan Li
    Communications in Theoretical Physics. 2024, 76(11): 115104. https://doi.org/10.1088/1572-9494/ad6de5
    Abstract (117) PDF (150) HTML (39)   Knowledge map   Save

    Imaginarity has proven to be a valuable resource in various quantum information processing tasks. A natural question arises: can the imaginarity of quantum states be broadcast via real operations? In this work, we present explicit structures for nonreal states whose imaginarity can be broadcast and cloned. That is, for a nonreal state, its imaginarity can be cloned if and only if it is a direct sum of several maximally imaginary states under orthogonal transformation, and its imaginarity can be broadcast if and only if it is a direct sum of a real state and some nonreal qubit states which are mixtures of two orthogonal maximally imaginary states under orthogonal transformation. In particular, we show that for a nonreal pure state, its imaginarity cannot be broadcast unless it is a maximally imaginary state. Furthermore, we derive a trade-off relation on the imaginarity broadcasting of pure states in terms of the measure of irreversibility of quantum states concerning real operations and the geometric measure of imaginarity. In addition, we demonstrate that any faithful measure of imaginarity is not superadditive.

  • Statistical Physics, Soft Matter and Biophysics
    Zhen Wang(王振), Weicheng Fu(符维成), Yong Zhang(张勇), Hong Zhao(赵鸿)
    Communications in Theoretical Physics. 2024, 76(11): 115601. https://doi.org/10.1088/1572-9494/ad696d
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    Thermalization in many-body systems, especially with strong interactions, is a central question in physics. In this work, we present a novel framework for the thermalization of interacting wave systems, distinguishing between trivial (no momentum exchange) and nontrivial interactions (significant energy redistribution). This distinction leads to a statistically equivalent model with weakened interactions. By applying this to FPUT-like models, we identify a unique double scaling of thermalization times. Crucially, our findings suggest the persistence of prethermalization in strong interactions.

  • Particle Physics and Quantum Field Theory
    Rong-Gen Cai, Katsuya Hashino, Shao-Jiang Wang, Jiang-Hao Yu
    Communications in Theoretical Physics. 2025, 77(5): 55204. https://doi.org/10.1088/1572-9494/ad9c3d
    Abstract (89) PDF (47) HTML (86)   Knowledge map   Save
  • Mathematical Physics
    Zhang-Lei Han, Jun-Yi Lao, Jia-Rui Zhang, Yu-Jia Shen
    Communications in Theoretical Physics. 2025, 77(4): 45001. https://doi.org/10.1088/1572-9494/ad8c27
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    Introducing ${ \mathcal P }{ \mathcal T }$-symmetric generalized Scarf-II potentials into the three-coupled nonlinear Gross–Pitaevskii equations offers a new way to seek stable soliton states in quasi-one-dimensional spin-1 Bose–Einstein condensates. In scenarios where the spin-independent parameter c0 and the spin-dependent parameter c2 vary, we use both analytical and numerical methods to investigate the three-coupled nonlinear Gross–Pitaevskii equations with ${ \mathcal P }{ \mathcal T }$-symmetric generalized Scarf-II potentials. We obtain analytical soliton states and find that simply modulating c2 may change the analytical soliton states from unstable to stable. Additionally, we obtain numerically stable double-hump soliton states propagating in the form of periodic oscillations, exhibiting distinct behavior in energy exchange. For further investigation, we discuss the interaction of numerical double-hump solitons with Gaussian solitons and observe the transfer of energy among the three components. These findings may contribute to a deeper understanding of solitons in Bose–Einstein condensates with ${ \mathcal P }{ \mathcal T }$-symmetric potentials and may hold significance for both theoretical understanding and experimental design in related physics experiments.

  • Mathematical Physics
    Zu-feng Liang, Xiao-yan Tang, Wei Ding
    Communications in Theoretical Physics. 2024, 76(11): 115001. https://doi.org/10.1088/1572-9494/ad6553
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    Considering the importance of higher-dimensional equations that are widely applied to real nonlinear problems, many (4 + 1)-dimensional integrable systems have been established by uplifting the dimensions of their corresponding lower-dimensional integrable equations. Recently, an integrable (4 + 1)-dimensional extension of the Boiti–Leon–Manna–Pempinelli (4DBLMP) equation has been proposed, which can also be considered as an extension of the famous Korteweg–de Vries equation that is applicable in fluids, plasma physics and so on. It is shown that new higher-dimensional variable separation solutions with several arbitrary lower-dimensional functions can also be obtained using the multilinear variable separation approach for the 4DBLMP equation. In addition, by taking advantage of the explicit expressions of the new solutions, versatile (4 + 1)-dimensional nonlinear wave excitations can be designed. As an illustration, periodic breathing lumps, multi-dromion-ring-type instantons, and hybrid waves on a doubly periodic wave background are discovered to reveal abundant nonlinear structures and dynamics in higher dimensions.

  • Others
    K Thulasidharan, N Sinthuja, N Vishnu Priya, M Senthilvelan
    Communications in Theoretical Physics. 2024, 76(11): 115801. https://doi.org/10.1088/1572-9494/ad6854
    Abstract (72) PDF (31) HTML (60)   Knowledge map   Save

    We introduce a novel neural network structure called strongly constrained theory-guided neural network (SCTgNN), to investigate the behaviour of the localized solutions of the generalized nonlinear Schrödinger (NLS) equation. This equation comprises four physically significant nonlinear evolution equations, namely, the NLS, Hirota, Lakshmanan–Porsezian–Daniel and fifth-order NLS equations. The generalized NLS equation demonstrates nonlinear effects up to quintic order, indicating rich and complex dynamics in various fields of physics. By combining concepts from the physics-informed neural network and theory-guided neural network (TgNN) models, the SCTgNN aims to enhance our understanding of complex phenomena, particularly within nonlinear systems that defy conventional patterns. To begin, we employ the TgNN method to predict the behaviour of localized waves, including solitons, rogue waves and breathers, within the generalized NLS equation. We then use the SCTgNN to predict the aforementioned localized solutions and calculate the mean square errors in both the SCTgNN and TgNN in predicting these three localized solutions. Our findings reveal that both models excel in understanding complex behaviour and provide predictions across a wide variety of situations.

  • Quantum Physics and Quantum Information
    Diego S Starke, Marcos L W Basso, Jonas Maziero
    Communications in Theoretical Physics. 2024, 76(9): 95101. https://doi.org/10.1088/1572-9494/ad5664
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    In [Phys. Rev. A 107 012427 (2023)], Baldwin and Jones prove that Uhlmann–Jozsa’s fidelity between two quantum states ρ and σ, i.e., $F(\rho ,\sigma )\,:= \,{\left({\rm{Tr}}\sqrt{\sqrt{\rho }\sigma \sqrt{\rho }}\right)}^{2}$, can be written in a simplified form as $F(\rho ,\sigma )={\left({\rm{Tr}}\sqrt{\rho \sigma }\right)}^{2}$. In this article, we give an alternative proof of this result, using a function power series expansion and the properties of the trace function. Our approach not only reinforces the validity of the simplified expression but also facilitates the exploration of novel dissimilarity functions for quantum states and more complex trace functions of density operators.

  • Quantum Physics and Quantum Information
    Xiang-You Chen, Tian Ye, Qing-Hu Chen
    Communications in Theoretical Physics. 2025, 77(5): 55101. https://doi.org/10.1088/1572-9494/ad9a89
    Abstract (61) PDF (38) HTML (47)   Knowledge map   Save
  • Mathematical Physics
    Weifang Weng, Zhenya Yan
    Communications in Theoretical Physics. 2025, 77(5): 55001. https://doi.org/10.1088/1572-9494/ad97ad
    Abstract (59) PDF (30) HTML (62)   Knowledge map   Save
  • Statistical Physics, Soft Matter and Biophysics
    Tian Tang, Chun-lai Ren, Yu-qiang Ma
    Communications in Theoretical Physics. 2025, 77(3): 35602. https://doi.org/10.1088/1572-9494/ad89ae
    Abstract (58) PDF (60) HTML (53)   Knowledge map   Save

    Active matter exhibits collective motions at various scales. Geometric confinement has been identified as an effective way to control and manipulate active fluids, with much attention given to external factors. However, the impact of the inherent properties of active particles on collective motion under confined conditions remains elusive. Here, we use a highly tunable active nematics model to study active systems under confinement, focusing on the effect of the self-driven speed of active particles. We identify three distinct states characterized by unique particle and flow fields within confined active nematic systems, among which circular rotation emerges as a collective motion involving rotational movement in both particle and flow fields. The theoretical phase diagram shows that increasing the self-driven speed of active particles significantly enhances the region of the circular rotation state and improves its stability. Our results provide insights into the formation of high quality vortices in confined active nematic systems.

  • Mathematical Physics
    Le Li, Wen-Juan Che, Xi-Zhe Liu, Chong Liu, Nail Akhmediev
    Communications in Theoretical Physics. 2025, 77(4): 45002. https://doi.org/10.1088/1572-9494/ad7ce6
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    We study fundamental dark-bright solitons and the interaction of vector nonlinear Schrödinger equations in both focusing and defocusing regimes. Classification of possible types of soliton solutions is given. There are two types of solitons in the defocusing case and four types of solitons in the focusing case. The number of possible variations of two-soliton solutions depends on this classification. We demonstrate that only special types of two-soliton solutions in the focusing regime can generate breathers of the scalar nonlinear Schrödinger equation. The cases of solitons with equal and unequal velocities in the superposition are considered. Numerical simulations confirm the validity of our exact solutions.

  • Mathematical Physics
    XiaoXia Yang, Lingling Xue, Q P Liu
    Communications in Theoretical Physics. 2024, 76(11): 115002. https://doi.org/10.1088/1572-9494/ad6a04
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    In this paper, we study the N = 2 a = 1 supersymmetric KdV equation. We construct its Darboux transformation and the associated Bäcklund transformation. Furthermore, we derive a nonlinear superposition formula, and as applications we calculate some solutions for this supersymmetric KdV equation and recover the related results for the Kersten–Krasil'shchik coupled KdV-mKdV system.

  • Quantum Physics and Quantum Information
    Jian Yan, Lin Chen
    Communications in Theoretical Physics. 2024, 76(9): 95102. https://doi.org/10.1088/1572-9494/ad43d2
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    Entanglement-breaking (EB) subspaces determine the additivity of entanglement of formation (EOF), which is a long-standing issue in quantum information. We explicitly construct the two-dimensional EB subspaces of any bipartite system, when system dimensions are equal, and we apply the subspaces to construct EB spaces of arbitrary dimensions. We also present partial construction when system dimensions are different. Then, we present the notion and properties of EB subspaces for some systems, and in particular the absolute EB subspaces. We construct some examples of absolute EB subspaces, as well as EB subspaces for some systems by using multiqubit Dicke states.

  • Mathematical Physics
    Jie-tong Li, Jun Yu, Xi-zhong Liu
    Communications in Theoretical Physics. 2025, 77(1): 15001. https://doi.org/10.1088/1572-9494/ad7cec
    Abstract (54) PDF (31) HTML (52)   Knowledge map   Save

    In this paper, the Drinfeld–Sokolov–Satsuma–Hirota (DSSH) system is studied by using residual symmetry and the consistent Riccati expansion (CRE) method, respectively. The residual symmetry of the DSSH system is localized to Lie point symmetry in a properly prolonged system, based on which we get a new Bäcklund transformation for this system. New symmetry reduction solutions of the DSSH system are obtained by applying the classical Lie group approach on the prolonged system. Moreover, the DSSH system proves to be CRE integrable and new interesting interaction solutions between solitons and periodic waves are generated and analyzed.

  • Quantum Physics and Quantum Information
    Lingxuan Feng, Shunlong Luo
    Communications in Theoretical Physics. 2025, 77(1): 15102. https://doi.org/10.1088/1572-9494/ad7942
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    We connect magic (non-stabilizer) states, symmetric informationally complete positive operator valued measures (SIC-POVMs), and mutually unbiased bases (MUBs) in the context of group frames, and study their interplay. Magic states are quantum resources in the stabilizer formalism of quantum computation. SIC-POVMs and MUBs are fundamental structures in quantum information theory with many applications in quantum foundations, quantum state tomography, and quantum cryptography, etc. In this work, we study group frames constructed from some prominent magic states, and further investigate their applications. Our method exploits the orbit of discrete Heisenberg–Weyl group acting on an initial fiducial state. We quantify the distance of the group frames from SIC-POVMs and MUBs, respectively. As a simple corollary, we reproduce a complete family of MUBs of any prime dimensional system by introducing the concept of MUB fiducial states, analogous to the well-known SIC-POVM fiducial states. We present an intuitive and direct construction of MUB fiducial states via quantum T-gates, and demonstrate that for the qubit system, there are twelve MUB fiducial states, which coincide with the H-type magic states. We compare MUB fiducial states and SIC-POVM fiducial states from the perspective of magic resource for stabilizer quantum computation. We further pose the challenging issue of identifying all MUB fiducial states in general dimensions.

  • Mathematical Physics
    Fazal Badshah, Kalim U Tariq, Ahmet Bekir, S M Raza Kazmi, Emad Az-Zo’bi
    Communications in Theoretical Physics. 2024, 76(9): 95001. https://doi.org/10.1088/1572-9494/ad5719
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    The nonlinear Schrödinger equation equation is one of the most important physical models used in optical fiber theory to explain the transmission of an optical soliton. The field of chiral soliton propagation in nuclear physics is very interesting because of its numerous applications in communications and ultra-fast signal routing systems. The (1+1)-dimensional chiral dynamical structure that describes the soliton behaviour in data transmission is dealt with in this work using a variety of in-depth analytical techniques. This work has applications in particle physics, ionised science, nuclear physics, optics, and other applied mathematical sciences. We are able to develop a variety of solutions to demonstrate the behaviour of solitary wave structures, periodic soliton solutions, chiral soliton solutions, and bell-shaped soliton solutions with the use of applied techniques. Moreover, in order to verify the scientific calculations, the stability analysis for the observed solutions of the governing model is taken into consideration. In addition, the 3-dimensional, contour, and 2-dimensional visuals are supplied for a better understanding of the behaviour of the solutions. The employed strategies are dependable, uncomplicated, and effective; yet have not been utilised with the governing model in the literature that is now accessible. The resulting outcomes have impressive applications across a large number of study areas and computational physics phenomena representing real-world scenarios. The methods applied in this model are not utilized on the given models in previous literature so we can say that these describe the novelty of the work.

  • Condensed Matter Theory
    Xing Wang, Xuechao Li
    Communications in Theoretical Physics. 2024, 76(9): 95702. https://doi.org/10.1088/1572-9494/ad4cdf
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    The third-harmonic generation (THG) coefficient for a spherical quantum dot system with inversely quadratic Hellmann plus inversely quadratic potential is investigated theoretically, considering the regulation of quantum size, confinement potential depth and the external environment. The numerical simulation results indicate that the THG coefficient can reach the order of 10−12 m2 V–2, which strongly relies on the tunable factor, with its resonant peak experiencing a redshift or blueshift. Interestingly, the effect of temperature on the THG coefficient in terms of peak location and size is consistent with the quantum dot radius but contrasts with the hydrostatic pressure. Thus, it is crucial to focus on the influence of internal and external parameters on nonlinear optical effects, and to implement the theory in practical experiments and the manufacture of optoelectronic devices.

  • Mathematical Physics
    Xiazhi Hao, S Y Lou
    Communications in Theoretical Physics. 2025, 77(2): 25001. https://doi.org/10.1088/1572-9494/ad84bd
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    In the realm of nonlinear integrable systems, the presence of decompositions facilitates the establishment of linear superposition solutions and the derivation of novel coupled systems exhibiting nonlinear integrability. By focusing on single-component decompositions within the potential BKP hierarchy, it has been observed that specific linear superpositions of decomposition solutions remain consistent with the underlying equations. Moreover, through the implementation of multi-component decompositions within the potential BKP hierarchy, successful endeavors have been undertaken to formulate linear superposition solutions and novel coupled KdV-type systems that resist decoupling via alterations in dependent variables.

  • Mathematical Physics
    Xi Chen, Wei-Qi Peng
    Communications in Theoretical Physics. 2025, 77(2): 25002. https://doi.org/10.1088/1572-9494/ad75f7
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    In this paper, the physics informed neural network (PINN) deep learning method is applied to solve two-dimensional nonlocal equations, including the partial reverse space y-nonlocal Mel'nikov equation, the partial reverse space-time nonlocal Mel'nikov equation and the nonlocal two-dimensional nonlinear Schrödinger (NLS) equation. By the PINN method, we successfully derive a data-driven two soliton solution, lump solution and rogue wave solution. Numerical simulation results indicate that the error range between the data-driven solution and the exact solution is relatively small, which verifies the effectiveness of the PINN deep learning method for solving high dimensional nonlocal equations. Moreover, the parameter discovery of the partial reverse space-time nonlocal Mel'nikov equation is analysed in terms of its soliton solution for the first time.

  • Quantum Physics and Quantum Information
    WenShan Xu, Ri-Gui Zhou, YaoChong Li, XiaoXue Zhang
    Communications in Theoretical Physics. 2024, 76(11): 115103. https://doi.org/10.1088/1572-9494/ad597d
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    Variational quantum algorithms are promising methods with the greatest potential to achieve quantum advantage, widely employed in the era of noisy intermediate-scale quantum computing. This study presents an advanced variational hybrid algorithm (EVQLSE) that leverages both quantum and classical computing paradigms to address the solution of linear equation systems. Initially, an innovative loss function is proposed, drawing inspiration from the similarity measure between two quantum states. This function exhibits a substantial improvement in computational complexity when benchmarked against the variational quantum linear solver. Subsequently, a specialized parameterized quantum circuit structure is presented for small-scale linear systems, which exhibits powerful expressive capabilities. Through rigorous numerical analysis, the expressiveness of this circuit structure is quantitatively assessed using a variational quantum regression algorithm, and it obtained the best score compared to the others. Moreover, the expansion in system size is accompanied by an increase in the number of parameters, placing considerable strain on the training process for the algorithm. To address this challenge, an optimization strategy known as quantum parameter sharing is introduced, which proficiently minimizes parameter volume while adhering to exacting precision standards. Finally, EVQLSE is successfully implemented on a quantum computing platform provided by IBM for the resolution of large-scale problems characterized by a dimensionality of 220.

  • Gravitation Theory, Astrophysics and Cosmology
    Ahmad Al-Badawi, Sohan Kumar Jha
    Communications in Theoretical Physics. 2024, 76(9): 95403. https://doi.org/10.1088/1572-9494/ad51ee
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    This article considers a static and spherical black hole (BH) in f(Q) gravity. f(Q) gravity is the extension of symmetric teleparallel general relativity, where both curvature and torsion are vanishing and gravity is described by nonmetricity. In this study, we investigate the possible implications of quasinormal mode (QNM) modified Hawking spectra and deflection angles generated by the model. The Wentzel–Kramers–Brillouin method is used to solve the equations of motion for massless Dirac perturbation fields and explore the impact of the nonmetricity parameter (Q0). Based on the QNM computation, we can ensure that the BH is stable against massless Dirac perturbations and as Q0 increases the oscillatory frequency of the mode decreases. We then discuss the weak deflection angle in the weak field limit approximation. We compute the deflection angle up to the fourth order of approximation and show how the nonmetricity parameter affects it. We find that the Q0 parameter reduces the deflection angle.

  • Particle Physics and Quantum Field Theory
    Xiaolan Meng, Bolun Hu, Yi-Bo Yang
    Communications in Theoretical Physics. 2024, 76(9): 95203. https://doi.org/10.1088/1572-9494/ad426f
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    We present a lattice quantum chromodynamics (QCD) simulation with 2 + 1 + 1 flavor full QCD ensembles using near-physical quark masses and different spatial sizes L, at a ∼ 0.055 fm. The results show that the scalar and pesudoscalar 2-point correlator with a valence pion mass of approximately 230 MeV become degenerated at L ≤ 1.0 fm, and such an observation suggests that the spontaneous chiral symmetry breaking disappears effectively at this point. At the same time, the mass gap between the nucleon and pion masses remains larger than ΛQCD in the entire L ∈ [0.2, 0.7] fm range.

  • Mathematical Physics
    Wenjing Li, Yi Zhang, Xiaolin Yang
    Communications in Theoretical Physics. 2024, 76(11): 115004. https://doi.org/10.1088/1572-9494/ad6e63
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    This article's purpose is to investigate multiple high-order pole solutions for the AB system by the Riemann–Hilbert (RH) approach. We establish the RH problem through using spectral analysis to the Lax pair. Then the RH problem can be resolved and the soliton solution's formula can be given by using the Laurent expansion method. Finally, we get special soliton solutions, including dark solitons, W-type dark solitons and multiple high-pole solutions. In addition, the W-type dark soliton solutions will occur when the spectral parameters are purely imaginary.

  • Condensed Matter Theory
    Ruofan Chen
    Communications in Theoretical Physics. 2024, 76(11): 115701. https://doi.org/10.1088/1572-9494/ad696b
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    Most path integral expressions for quantum open systems are formulated with diagonal system-bath coupling, where the influence functional is a functional of scalar-valued trajectories. This formalism is enough if only a single bath is under consideration. However, when multiple baths are present, non-diagonal system-bath couplings need to be taken into consideration. In such a situation, using an abstract Liouvillian method, the influence functional can be obtained as a functional of operator-valued trajectories. The value of the influence functional itself also becomes a superoperator rather than an ordinary scalar, whose meaning is ambiguous at first glance and its connection to the conventional understanding of the influence functional needs extra careful consideration. In this article, we present another concrete derivation of the superoperator-valued influence functional based on the straightforward Trotter–Suzuki splitting, which can provide a clear picture to interpret the superoperator-valued influence functional.

  • Gravitation Theory, Astrophysics and Cosmology
    M Yousaf, Bander Almutairi, M Z Bhatti, Z Yousaf, A S Khan
    Communications in Theoretical Physics. 2025, 77(3): 35403. https://doi.org/10.1088/1572-9494/ad873f
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    In this work, we consider the collapse of a ${\mathbb{D}}$-dimensional sphere in the framework of a higher-dimensional spherically symmetric space-time in which the gravitational action chosen is claimed to be somehow linked to the ${\mathbb{D}}$-dimensional modified term. This work investigates the criteria for the dynamical instability of anisotropic relativistic sphere systems with ${\mathbb{D}}$-dimensional modified gravity. The certain conditions are applied that lead to the collapse equation and their effects on adiabatic index Γ in both Newtonian (N) and Post-Newtonian (PN) regimes by using a perturbation scheme. The study explores that the Γ plays a crucial role in determining the degree of dynamical instability. This index characterizes the fluid’s stiffness and has a significant impact on defining the ranges of instability. This systematic investigation demonstrates the influence of various material properties such as anisotropic pressure, kinematic quantities, mass function, ${\mathbb{D}}$-dimensional modified gravity parameters, and the radial profile of energy density on the instability of considered structures during their evolution. This work also displays the dynamical behavior of spherically symmetric fluid configuration via graphical approaches.

  • Mathematical Physics
    Zhao Zhao, Bo Ren
    Communications in Theoretical Physics. 2025, 77(3): 35001. https://doi.org/10.1088/1572-9494/ad8740
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    The main focus of this paper is to address a generalized (2+1)-dimensional Hirota bilinear equation utilizing the bilinear neural network method. The paper presents the periodic solutions through a single-layer model of [3-4-1], followed by breather, lump and their interaction solutions by using double-layer models of [3-3-2-1] and [3-3-3-1], respectively. A significant innovation introduced in this work is the computation of periodic cross-rational solutions through the design of a novel [3-(2+2)-4-1] model, where a specific hidden layer is partitioned into two segments for subsequent operations. Three-dimensional and density figures of the solutions are given alongside an analysis of the dynamics of these solutions.

  • Particle Physics and Quantum Field Theory
    Yuanhong Guo, Lei Wang, Gang Yang
    Communications in Theoretical Physics. 2025, 77(5): 55203. https://doi.org/10.1088/1572-9494/ada916
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  • Atomic, Molecular, Optical (AMO) and Plasma Physics, Chemical Physics
    Sheng Wang, Zhehao Zhang, Xi-Wen Guan
    Communications in Theoretical Physics. 2025, 77(5): 55502. https://doi.org/10.1088/1572-9494/ad93b6
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  • Quantum Physics and Quantum Information
    Jin-Ze Li, Ming-Hao Wang, Bin Zhou
    Communications in Theoretical Physics. 2025, 77(3): 35102. https://doi.org/10.1088/1572-9494/ad89ac
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    Since the concept of quantum information masking was proposed by Modi et al (2018 Phys. Rev. Lett. 120, 230 501), many interesting and significant results have been reported, both theoretically and experimentally. However, designing a quantum information masker is not an easy task, especially for larger systems. In this paper, we propose a variational quantum algorithm to resolve this problem. Specifically, our algorithm is a hybrid quantum–classical model, where the quantum device with adjustable parameters tries to mask quantum information and the classical device evaluates the performance of the quantum device and optimizes its parameters. After optimization, the quantum device behaves as an optimal masker. The loss value during optimization can be used to characterize the performance of the masker. In particular, if the loss value converges to zero, we obtain a perfect masker that completely masks the quantum information generated by the quantum information source, otherwise, the perfect masker does not exist and the subsystems always contain the original information. Nevertheless, these resulting maskers are still optimal. Quantum parallelism is utilized to reduce quantum state preparations and measurements. Our study paves the way for wide application of quantum information masking, and some of the techniques used in this study may have potential applications in quantum information processing.

  • Mathematical Physics
    Yilin Wang, Biao Li
    Communications in Theoretical Physics. 2024, 76(11): 115003. https://doi.org/10.1088/1572-9494/ad6b1c
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    We construct the Riemann–Hilbert problem of the Lakshmanan–Porsezian–Daniel equation with nonzero boundary conditions, and use the Laurent expansion and Taylor series expansion to obtain the exact formulas of the soliton solutions in the case of a higher-order pole and multiple higher-order poles. The dynamic behaviors of a simple pole, a second-order pole and a simple pole plus a second-order pole are demonstrated.

  • Quantum Physics and Quantum Information
    Xiaoqi Liu, Yuedi Qu, Ming Li, Shu-Qian Shen
    Communications in Theoretical Physics. 2025, 77(4): 45101. https://doi.org/10.1088/1572-9494/ad8bae
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    To solve the Poisson equation it is usually possible to discretize it into solving the corresponding linear system Ax = b. Variational quantum algorithms (VQAs) for the discretized Poisson equation have been studied before. We present a VQA based on the banded Toeplitz systems for solving the Poisson equation with respect to the structural features of matrix A. In detail, we decompose the matrices A and A2 into a linear combination of the corresponding banded Toeplitz matrix and sparse matrices with only a few non-zero elements. For the one-dimensional Poisson equation with different boundary conditions and the d-dimensional Poisson equation with Dirichlet boundary conditions, the number of decomposition terms is less than that reported in [Phys. Rev. A 2023 108, 032 418 ]. Based on the decomposition of the matrix, we design quantum circuits that efficiently evaluate the cost function. Additionally, numerical simulation verifies the feasibility of the proposed algorithm. Finally, the VQAs for linear systems of equations and matrix-vector multiplications with the K-banded Toeplitz matrix TnK are given, where ${T}_{n}^{K}\in {R}^{n\times n}$ and $K\in O(\mathrm{ploylog}n)$ .

  • Gravitation Theory, Astrophysics and Cosmology
    Sana Malik, Abdul Jawad, Shahid Chaudhary, Mohammad Mahtab Alam, Sanjar Shaymatov, Shamaila Rani
    Communications in Theoretical Physics. 2025, 77(4): 45404. https://doi.org/10.1088/1572-9494/ad91b1
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    We assume exponential corrections to the entropy of 5D charged AdS black hole solutions, which are derived within the framework of Einstein–Gauss–Bonnet gravity and nonlinear electrodynamics. Additionally, we consider two distinct versions of 5D charged AdS black holes by setting the parameters q → 0 and k → 0 (where q represents the charge, and k is the non-linear parameter). We investigate these black holes in the extended phase space, where the cosmological constant is interpreted as pressure, demonstrating the first law of black hole thermodynamics. The focus extends to understanding the thermal stability or instability, as well as identifying first and second-order phase transitions. This exploration is carried out through the analysis of various thermodynamic quantities, including heat capacity at constant pressure, Gibbs free energy (GFE), Helmholtz free energy (HFE), and the trace of the Hessian matrix. In order to visualize phase transitions, identify critical points, analyze stability and provide comprehensive analysis, we have made the contour plot of the mentioned thermodynamic quantities and observed that our results are very consistent. These investigations are conducted within the context of exponentially corrected entropies, providing valuable insights into the intricate thermodynamic behavior of these 5D charged AdS black holes under different parameter limits.

  • Topical Review: Gravitation Theory, Astrophysics and Cosmology
    Peixiang Ji, Lijing Shao
    Communications in Theoretical Physics. 2024, 76(10): 107401. https://doi.org/10.1088/1572-9494/ad5aeb
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    The reason for the present accelerated expansion of the Universe stands as one of the most profound questions in the realm of science, with deep connections to both cosmology and fundamental physics. From a cosmological point of view, physical models aimed at elucidating the observed expansion can be categorized into two major classes: dark energy and modified gravity. We review various major approaches that employ a single scalar field to account for the accelerating phase of our present Universe. Dynamic system analysis was employed in several important models to find cosmological solutions that exhibit an accelerating phase as an attractor. For scalar field models of dark energy, we consistently focused on addressing challenges related to the fine-tuning and coincidence problems in cosmology, as well as exploring potential solutions to them. For scalar–tensor theories and their generalizations, we emphasize the importance of constraints on theoretical parameters to ensure overall consistency with experimental tests. Models or theories that could potentially explain the Hubble tension are also emphasized throughout this review.

  • Gravitation Theory, Astrophysics and Cosmology
    Susobhan Mandal
    Communications in Theoretical Physics. 2024, 76(9): 95406. https://doi.org/10.1088/1572-9494/ad582b
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    Scalar-tensor theories of gravity are considered to be competitors to Einstein's theory of general relativity for the description of classical gravity, as they are used to build feasible models for cosmic inflation. These theories can be formulated both in the Jordan and Einstein frame, which are related by a Weyl transformation with a field transformation, known together as a frame transformation. These theories formulated in the above two frames are often considered to be equivalent from the point of view of classical theory. However, this is no longer true from the quantum field theoretical perspective. In the present article, we show that the Ward identities derived in the above two frames are not connected through the frame transformation. This shows that the quantum field theories formulated in these two frames are not equivalent to each other. Moreover, this inequivalence is also shown by comparing the effective actions derived in these two frames.

  • Gravitation Theory, Astrophysics and Cosmology
    Qiyun Fu, Tieyan Si
    Communications in Theoretical Physics. 2025, 77(4): 45401. https://doi.org/10.1088/1572-9494/ad8db9
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    We simulate the gravitational redshift of quantum matter waves with a long de Broglie wavelength by tracing particle beams along geodesics, when they propagate within the rotation plane of binary black holes. The angular momentum of the binary black hole causes an asymmetric gravitational redshift distribution around the two black holes. The gravitational redshift changes the frequency of quantum matter waves and their wavelength, resulting in the different interference patterns of quantum matter waves with respect to different wavelengths. The interference pattern demonstrates strong contrast intensity and spatial order with respect to different wavelengths and the rotational angle of the binary black hole. A bright semicircular arc emerges from the interference pattern to bridge the two black holes, when they rotate to certain angles, which provides a theoretical understanding on the gravitational lensing effect of quantum matter waves.

  • Statistical Physics, Soft Matter and Biophysics
    Bing Yang(杨冰), Yanting Wang(王延颋)
    Communications in Theoretical Physics. 2025, 77(6): 67601. https://doi.org/10.1088/1572-9494/ada429
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  • Particle Physics and Quantum Field Theory
    Guo-Qiang Dai, Chong-Xing Yue, Yang-Yang Bu, Yi-Hang Wang
    Communications in Theoretical Physics. 2024, 76(9): 95202. https://doi.org/10.1088/1572-9494/ad5277
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    The axion-like particle (ALP) is one kind of the best-motivated new particles. We consider its production from the pseudoscalar mesonic decays $M\to M^{\prime} a$, with M being a pseudoscalar meson B or K. The upper limits on the flavor-conserving ALP–quark coupling parameter gu are obtained by assuming the ALP to be an invisible particle. We find that the most severe constraint on gu comes from the decay ${K}^{+}\to {\pi }^{+}\nu \bar{\nu }$ for 0.05 GeV ≤ Ma ≤ 0.35 GeV, while the decays ${B}^{+,0}\to {K}^{+,0}\nu \bar{\nu }$ and ${B}^{+,0}\to {\pi }^{+,0}\nu \bar{\nu }$ can also generate significant constraints.

  • Quantum Physics and Quantum Information
    Yaru Liu, Peng Zhang
    Communications in Theoretical Physics. 2024, 76(11): 115102. https://doi.org/10.1088/1572-9494/ad6550
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    The eikonal approximation (EA) is widely used in various high-energy scattering problems. In this work we generalize this approximation from the scattering problems with time-independent Hamiltonian to the ones with periodical Hamiltonians, i.e., the Floquet scattering problems. We further illustrate the applicability of our generalized EA via the scattering problem with respect to a shaking spherical square-well potential, by comparing the results given by this approximation and the exact ones. The generalized EA we developed is helpful for the research of manipulation of high-energy scattering processes with external field, e.g. the manipulation of atom, molecule or nuclear collisions or reactions via strong laser fields.

  • Atomic, Molecular, Optical (AMO) and Plasma Physics, Chemical Physics
    Shahana Rizvi, Muhammad Afzal
    Communications in Theoretical Physics. 2024, 76(11): 115502. https://doi.org/10.1088/1572-9494/ad666d
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    This study analyzes the scattering of electromagnetic waves in a cold and uniform plasma-filled waveguide driven by an intense relativistic plasma beam under a strong magnetic field. The strong interaction of plasma with electromagnetic waves enables its potential use in different types of waveguides. The Helmholtz equation governs the boundary value problem, which is solved by incorporating the mode matching technique. Invoking the boundary and matching conditions and the derived orthogonality and dispersion relations in this scheme gives an exact solution to the scattering problem. The numerical results shed light on the occurrence of reflection and transmission and flow of power. The power flux is plotted against angular frequency and various duct configurations. The solution is completely validated through the benefit of analytical and numerical results. The investigation of this structure reveals not only its mathematical, but also its physical features.

  • Mathematical Physics
    Xin Wang, Jingsong He
    Communications in Theoretical Physics. 2025, 77(3): 35003. https://doi.org/10.1088/1572-9494/ad84be
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    We investigate dark solitons lying on elliptic function background in the defocusing Hirota equation with third-order dispersion and self-steepening terms. By means of the modified squared wavefunction method, we obtain the Jacobi’s elliptic solution of the defocusing Hirota equation, and solve the related linear matrix eigenvalue problem on elliptic function background. The elliptic N-dark soliton solution in terms of theta functions is constructed by the Darboux transformation and limit technique. The asymptotic dynamical behaviors for the elliptic N-dark soliton solution as t → ± ∞ are studied. Through numerical plots of the elliptic one-, two- and three-dark solitons, the amplification effect on the velocity of elliptic dark solitons, and the compression effect on the soliton spatiotemporal distributions produced by the third-order dispersion and self-steepening terms are discussed.