International Journal of Theoretical Physics最新文献

{"title":"Investigation of Quantum Lenoir Engine Efficiency of Non-relativistic and Relativistic Quantum Systems in Pure- and Mixed-state Formalisms","authors":"Yuni Setiasari,&nbsp;Eny Latifah,&nbsp;Hari Wisodo,&nbsp;Arif Hidayat,&nbsp;Yunita Kristanti Andriani,&nbsp;Agus Purwanto,&nbsp;Heru Sukamto","doi":"10.1007/s10773-026-06470-7","DOIUrl":"10.1007/s10773-026-06470-7","url":null,"abstract":"<div><p>In this study, we consider a two-state single particle confined in a one-dimensional box system undergoing a Lenoir cycle. The quantum system is represented as a set of canonical ensembles, and thus the mixed-state probability distribution of the particle is described by the Maxwell-Boltzmann distribution. We calculate the efficiency formulations for relativistic and non-relativistic working substances and analyze the associated physical parameters therein. We also compare the results with those obtained from a quantum Lenoir engine using a pure-state working substance and classical working substances. We found that the non-relativistic working substance has a higher efficiency than the relativistic and classical working substances at the same compression ratio. The higher compression ratio increases efficiency among all types of working substances studied. Furthermore, a quantum Lenoir engine using a mixed-state working substance has the same efficiency formulation as that of the pure-state working substance, but with a limited compression ratio. The efficiency of the mixed-state working substance depends on two physical parameters, viz., the reservoir temperature ratio and the initial box width, regardless of the initial temperature. While a very high temperature ratio can enhance this efficiency, it remains lower than that of the pure-state working substance for the same two-state quantum system.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-Depth Fixed-Layer Variational Quantum Eigensolver for Small Transverse-Field Ising Ground States","authors":"Fuzhou Wang,&nbsp;Xianhua Song,&nbsp;Zhixin Zhang","doi":"10.1007/s10773-026-06487-y","DOIUrl":"10.1007/s10773-026-06487-y","url":null,"abstract":"<div><p>Exact diagonalization provides exact spectra and ground-state references for small quantum many-body systems, but its cost grows rapidly with Hilbert-space dimension. This paper studies a fixed low-depth unitary circuit as a variational ansatz for approximating ground states of small transverse-field Ising-model (TFIM) systems. Each of the <i>N</i> qubits contains three rotation gates in each of the <i>L</i> layers and each rotation gate contains a trainable parameter, yielding a total of 3<i>NL</i> tunable parameters. And a PyTorch-based Variational Quantum Eigensolver (PyTorch-VQE), optimized with Adam and automatic differentiation, is evaluated in CPU simulations for open chains with different system sizes <i>N</i>, nearest-neighbor coupling strengths <i>J</i>, transverse-field strengths <i>h</i>, circuit depths <i>L</i>, and five fixed initializations per setting. Exact diagonalization supplies the ground-state energy and vector used to evaluate the variational approximation. Across the 27 tested settings, the three-depth circuit gives a mean relative ground-state energy error of <span>(0.598%)</span> and a mean fidelity of <span>(90.466%)</span>. These results demonstrate that the selected fixed-depth ansatz can well approximates ground states for the tested small TFIM systems.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantum Speed Limits Based on Quantifiers of Quantum-State Texture","authors":"Yuhang Xie,&nbsp;Yanjun Chu,&nbsp;Chenyang Cui,&nbsp;Shao-Ming Fei","doi":"10.1007/s10773-026-06489-w","DOIUrl":"10.1007/s10773-026-06489-w","url":null,"abstract":"<div><p>Quantum speed limits impose intrinsic lower bounds on the shortest time scale for quantum system evolution. As an emerging paradigm in quantum resource theory, quantum-state texture has attracted research interest amid the rapid advancement of quantum theory. Herein, we investigate the interplay between quantum speed limits and quantum-state texture via several canonical quantifiers, including trace distance, state rugosity and Jensen-Shannon divergence. To demonstrate our findings, we analyze the minimum evolution time of physical systems subject to dephasing and dissipative dynamics. For the Jensen-Shannon divergence, we further explore nonunitary dynamics described by completely positive and trace-preserving maps, taking the amplitude damping channel as a typical example. In addition, we explore the tightness of these bounds in the considered dynamical models. Our results reveal that quantum speed limits derived from quantum-state texture capture the fundamental constraints on quantum evolutionary speed, with promising applications in quantum computing, quantum control and quantum metrology.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148974779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Qualitative Dynamics and Exact Traveling-Wave Solutions of the Nonlinear Black–Scholes Equation","authors":"Karmina K. Ali,&nbsp;Niazy H. Hussein","doi":"10.1007/s10773-026-06471-6","DOIUrl":"10.1007/s10773-026-06471-6","url":null,"abstract":"<div><p>The extended nonlinear Black-Scholes equation is a significant modification of the conventional option-pricing model that incorporates nonlinear market effects caused by transaction costs, liquidity limitations, and feedback mechanisms. In this paper, we give a complete qualitative and analytical analysis of this model utilizing nonlinear dynamical systems theory. A traveling-wave transformation converts the governing partial differential equation into an autonomous planar system with an equilibrium structure, local stability, and Hamiltonian formulation determined by an appropriate conservative condition. The resulting first integral allows for a comprehensive phase-space analysis and the derivation of accurate traveling-wave solutions. Specifically, explicit Jacobi elliptic solutions are found, while the classical solitary wave is recovered as the limiting homoclinic orbit, indicating that localized and periodic waves belong to the same family of Hamiltonian solutions. Global phase portraits are created to demonstrate the qualitative influence of solution trajectories on model parameters and to offer a geometric interpretation of analytical solutions. The periodically driven system is statistically explored using Poincaré sections and bifurcation diagrams, demonstrating the breakdown of invariant tori and the emergence of Hamiltonian chaos as the forcing amplitude grows. The proposed Hamiltonian framework combines equilibrium analysis, accurate traveling-wave solutions, global phase pictures, and chaotic dynamics into a single theoretical environment. This methodology offers a systematic way to researching nonlinear option-pricing models and is easily applicable to other nonlinear evolution equations in applied mathematics and mathematical finance.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing Entanglement and Quantum Chaos Operator in Dirac and Graphene Quantum Systems with SU(3) Casimir Measurement","authors":"Abdelmalek Bouzenada","doi":"10.1007/s10773-026-06484-1","DOIUrl":"10.1007/s10773-026-06484-1","url":null,"abstract":"<div><p>We develop a unified theoretical framework for symmetry-resolved entanglement, its geometric formulation in curved spacetime, and its dynamical relation to quantum chaos. We formulate the entanglement asymmetry model and establish a replica-based path-integral construction for the exact evaluation of symmetry-resolved entanglement measures. The framework is extended to quantum field theory in curved spacetime, where the interplay between spacetime geometry, internal symmetries, and quantum correlations is incorporated systematically. In particular, we construct the <i>SU</i>(3) symmetry-resolved decomposition using irreducible representations, quadratic and higher-order Casimir invariants, and Casimir-weighted projection operators, providing an exact representation-theoretic characterization of the entanglement structure. We then investigate the dynamical evolution of entanglement and its connection with the emergence of quantum chaos by introducing a quantum chaos operator and deriving its exact form in <span>(mathcal {D})</span> dimensions. The operator is subsequently incorporated into the Dirac equation in <span>(mathcal {D})</span> dimensions and evaluated explicitly for graphene Dirac fermions, establishing a direct connection between relativistic quantum dynamics, symmetry-resolved entanglement, and chaotic evolution. We further examine the domain of applicability of the construction under strong disorder, strong interactions, finite temperature, and finite density, and discuss its extension to nonequilibrium states and open quantum systems. These results provide a general framework for analyzing symmetry-resolved quantum correlations and their dynamical degradation in relativistic and condensed-matter quantum systems, with potential applications to quantum field theory in curved spacetime, Dirac materials, and quantum information in strongly correlated and chaotic regimes.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From Symmetries to Conformal Minkowski Space-Time: Construction via (P backslash O(n,2)) and Implications to Gauge Gravity","authors":"Sao Leija Flores,&nbsp;Pablo César Rodríguez Ramírez,&nbsp;Prihel Cavildo Sánchez,&nbsp;Raúl Gómez Muñoz","doi":"10.1007/s10773-026-06475-2","DOIUrl":"10.1007/s10773-026-06475-2","url":null,"abstract":"<div><p>Starting from conformal Minkowski space as the projective null quadric in <span>(mathbb {R}^{n,2})</span>, we construct an explicit four-chart atlas for the compactified spacetime, in contrast with the usual two-chart descriptions found in the literature. We also use explicitly the homogeneous-coordinate system dictated by the homogeneous-space structure associated with a parabolic subgroup <span>(Psubset G=O(n,2))</span>; in the matrix conventions used below, this space is realized as <span>(Pbackslash G)</span>, so that the geometry is genuinely treated through the quotient structure rather than through a single affine patch. This global construction reveals geometric structures that are not visible in the standard local description and clarifies their implications for natural gauge-gravity theories on conformal Minkowski space. In particular, the Lorentz and dilation sectors arise canonically as local actions on the fiber of the induced bundle, whereas translations and special conformal transformations are encoded through the base geometry and transition maps; they do not appear as canonical independent local gauge actions on the fiber in this induced-bundle construction. Consequently, gauge-gravity models built in this framework without a soldering form or vielbein are naturally restricted to topological-type structures, as is generally expected when no soldering mechanism is present. Since the construction is canonical, it also reproduces the standard background of Minkowskian conformal field theory, including conformal weights, field transformations, compactification, and conformal generators. As a concrete test of the usefulness of this global description, we additionally develop a scalar holographic example. The normalized spherical vector is first realized as a globally compatible section in all four boundary charts and is then extended into the projective AdS bulk by the same <i>A</i>- and <i>N</i>-directions that organize the conformal representation. The resulting expression is the standard scalar boundary-to-bulk kernel in the present light-cone coordinates. In the explicit <span>(n=2)</span> case, the kernel also produces a consistent family of bulk transition factors whose radial limit recovers the scalar principal-series gluing data on <span>(Pbackslash G)</span>. The point of the calculation is not to introduce a new scalar propagator, but to exhibit explicitly how global conformal geometry, induced representations, and a familiar AdS/CFT quantity fit into one calculational framework.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Kähler and Quaternion-Kähler Spacetime Structure","authors":"R. Vilela Mendes","doi":"10.1007/s10773-026-06482-3","DOIUrl":"10.1007/s10773-026-06482-3","url":null,"abstract":"<div><p>When real Lorentzian spacetime is embedded into a manifold parametrized by higher division algebras (complex or quaternion with Hermitean metric) and the representation constraints of their symmetry groups are made compatible, a set of quantum numbers is generated that is evocative of those of the standard model of particle physics. This is taken as a hint that in spacetime there is a pseudo-Kähler or pseudo-quaternion-Kähler structure, real spacetime being a submanifold that inherits the symmetry contraints of the larger ambient manifold.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Qualitative Analysis and Semi-Analytical Solution of the Time Fractional FitzHugh–Nagumo Equation","authors":"Sanjeev Yadav,&nbsp;Ramesh Kumar Vats","doi":"10.1007/s10773-026-06478-z","DOIUrl":"10.1007/s10773-026-06478-z","url":null,"abstract":"<div><p>The FitzHugh–Nagumo equation provides a fundamental mathematical framework for analyzing the propagation of electrical signals in excitable media, particularly in nerve fibers. Caputo fractional derivative is used in the formulation of nonlinear Time Fractional Fitzhugh–Nagumo (TFFN) dynamical system. We establish the existence and uniqueness of solutions for this equation by applying the Banach fixed point theorem. Furthermore, we demonstrate the asymptotic stability of these solutions using the Lyapunov direct method. Laplace Residual Power Series (LRPS) method is used to obtain fractional series solution of TFFN equation. To illustrate the accuracy and efficiency of the LRPS method, we provide tabular and graphical results for different orders of fractional derivative and compare them with other existing methods like Modified Taylor Series Method (MTSM) and Residual Power Series Method (RPSM), Fractional Reduced Differential Transform Method (FRDTM). These results are calculated by using Maple and Matlab software. Also, it is worth noticing that the behavior of the solution demonstrates that changing the fractional order reflects the nature of the solution.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Construction of Soliton and Lump Solutions for (2+1)-dimensional CBS Equation and EGPINN-based Numerical Learning","authors":"Xiaoshu Xie,&nbsp;Xiaohan Gong,&nbsp;Yingying Zhang,&nbsp;Xiangpeng Xin","doi":"10.1007/s10773-026-06465-4","DOIUrl":"10.1007/s10773-026-06465-4","url":null,"abstract":"<div><p>Over the past few years, diverse special analytical forms of partial differential equations—such as soliton and lump analytical solutions—have drawn substantial research interest once more. Centering on the (2+1)-dimensional Calogero-Bogoyavlenskii-Schiff (CBS) equation, the present work aims to derive its analytical exact solutions and carry out corresponding numerical simulation research. We first adopt the Hirota bilinear technique to deduce multi-soliton analytical expressions for the CBS equation, covering single, two-soliton and three-soliton scenarios. On this basis, we employ the long-wave limit approach to build a single lump solution. Via visualized comparative analysis, we confirm that the amplitude, wave profile and propagation orientation of this lump solution throughout its transmission process. Afterwards, we take the physical informed neural network (PINN) and its improved variant extended physical informed graph neural network (EGPINN) as numerical learning tools, and apply them to analyze several of the above-derived soliton solutions. The whole EGPINN framework is divided into four core modules: dataset generation, model architecture design, training parameter optimization and outcome validation. Comparative numerical tests demonstrate that the forecasts yielded by EGPINN match well with the theoretically derived analytical solutions. When contrasted with conventional PINN frameworks, our EGPINN achieves better performance in capturing local physical features, boosting calculation speed, supporting multi-model fusion and enhancing prediction precision. This work therefore offers a reliable numerical computation tool for fast simulation of complicated nonlinear partial differential systems.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Comparative Study of Nonlinear Weyl-type f(Q, T) Gravity and (Lambda )CDM Models with Observational Constraints","authors":"Dinesh Chandra Maurya","doi":"10.1007/s10773-026-06481-4","DOIUrl":"10.1007/s10773-026-06481-4","url":null,"abstract":"<div><p>The cosmological models in modified gravity theories may challenge the <span>(Lambda )</span>CDM standard model. In this paper, we investigate such a modified gravity theory called the Weyl-type <i>f</i>(<i>Q</i>, <i>T</i>) gravity model in comparison to the standard <span>(Lambda )</span>CDM model. We propose that a nonlinear form of a Weyl-type <i>f</i>(<i>Q</i>, <i>T</i>) gravity function can explain the late-time accelerating scenarios of the expanding universe without inclusion of cosmological constant <span>(Lambda )</span> and exotic fluid sources. We consider the particular case for <span>(f(Q,T)=mu ,Q+2eta frac{H_{0}^{4}}{Q}+frac{epsilon }{kappa ^{2}},T)</span>, where <span>(mu )</span>, <span>(eta )</span>, and <span>(epsilon )</span> are the dimensionless coupling constants. We solve field equations for the Hubble function <i>H</i>(<i>z</i>) and obtain the constrained values of model parameters using joint analysis of cosmic chronometer sample of <i>H</i>(<i>z</i>) dataset and Pantheon+SH0ES samples of SNe Ia datasets by applying the Monte Carlo Markov chain technique in emcee software. We found that a nonlinear Weyl-type <span>( f(Q,T) )</span> gravity model could potentially address the dark energy problem. This model includes several key parameters estimations: the Hubble constant <span>( H_{0} = 72.08 pm 0.88 )</span> km/s/Mpc, the matter energy density parameter <span>( Omega _textrm{m0} = 0.278^{+0.110}_{-0.061} )</span>, <span>( eta = -3.4 pm 1.1 )</span>, <span>( epsilon = 0.71^{+0.26}_{-0.12} )</span>, the deceleration parameter <span>( q_{0} = -0.4963 )</span>, the effective equation of state <span>( omega _textrm{eff0} = -0.6642 )</span>, the transition redshift <span>( z_{t} = 0.7225 )</span>, and the dynamical Lagrange multiplier <span>( lambda (z) )</span> with effective dynamical mass <span>(m_textrm{eff})</span> revealing the particle creation scenario during the matter-geometry interaction. Also, we have investigated the behavior of jerk parameter <i>j</i>(<i>z</i>), om diagnostic function <i>Om</i>(<i>z</i>), and age of the universe. We have found the present age of the universe <span>(t_{0}=14.10^{+1.46}_{-1.14})</span> Gyrs.</p></div>","PeriodicalId":597,"journal":{"name":"International Journal of Theoretical Physics","volume":"65 9","pages":""},"PeriodicalIF":2.3,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}