Journal of Experimental and Theoretical Physics最新文献

{"title":"Linear Stability Analysis of Hydraulic Jump in an Open Channel Flow","authors":"Pratik D. Jiwane,&nbsp;Avinash D. Vasudeo,&nbsp;Arun Kumar Singh","doi":"10.1134/S1063776126600042","DOIUrl":"10.1134/S1063776126600042","url":null,"abstract":"<p>Hydraulic jump is an important phenomenon in water resource engineering. Present study involves linear stability analysis of St. Venant equations for hydraulic jump in an open channel under steady flow conditions. Frequency of perturbed flow is studied numerically with respect to flow depth and Froude number (<i>Fr</i>). It is observed that angular frequency (ω₀) of flow achieves the peak at critical Froude number <i>Fr</i> = 1. Effect of roughness coefficient and bed slope on the frequency of the flow reveals that frequency peak increases with roughness coefficient, but an increase in bed slope reduces the frequency. Further, study of the characteristics of angular frequency (ω₀) and wave number (<i>k</i>) of hydraulic jump shows the stability in supercritical, subcritical and critical flow regimes. The study shows the propagation of perturbations in different flow regimes and the effects on the stability due to influence of roughness and slope.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"168 - 177"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865793","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":"Exploring a Universe Model by Gravitational Decoupling in a Modified Gravity","authors":"M. Sharif,&nbsp;E. M. Moneer,&nbsp;M. Sallah,&nbsp;E. E. Zotos","doi":"10.1134/S1063776125602101","DOIUrl":"10.1134/S1063776125602101","url":null,"abstract":"<p>This work presents an anisotropic cosmological model constructed within the framework of Rastall gravity by applying the gravitational decoupling method to a time-dependent spherically symmetric spacetime. Utilizing the minimal deformation approach, we decouple the field equations corresponding to an extended matter distribution into two separate systems: one governing the original (seed) source and the other describing the additional source introduced through decoupling. The seed sector is solved by adopting a specific <span>(mathbb{E}{text{o}}mathbb{S})</span> that establishes a relationship between energy density and isotropic pressure, consistent with the anisotropic Bianchi-I cosmology. The equations for the additional source are then addressed under a prescribed density condition, with the decoupling parameter playing a key role. The integration of these solutions leads to an anisotropic cosmological extension. To assess the physical viability of the model, we analyze its dynamical behavior across three cosmological epochs, each defined by distinct <span>(mathbb{E}{text{o}}mathbb{S})</span> parameter values and fixed choices of Rastall and decoupling parameters. Our findings indicate that the model remains stable and physically plausible during the matter- and radiation-dominated periods but does not meet these standards in the dark energy-dominated era.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"152 - 167"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865795","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":"Aluminum Nitride Nanosheets with Defects as a Supercapacitor Electrode Material: a DFT Study","authors":"Dheeraj Kumar Pandey,&nbsp;Sudhanshu Pandey","doi":"10.1134/S1063776125602071","DOIUrl":"10.1134/S1063776125602071","url":null,"abstract":"<p>The quantum capacitance characteristics of defective aluminum nitride nanosheets (AlNNS) are examined in this study with an emphasis on their possible application in supercapacitors. Using phonon spectrum analysis and cohesive energy calculations, we confirmed the structural integrity of the primitive cell. Our results show that thin monolayers with nitrogen (N), aluminum (Al), or AlN deficits exhibit either narrow-bandgap semiconducting behavior or metallic properties. Defect formation energy calculations suggest that the best choice is N-deficient AlNNS. New impurity states around the Fermi level arise as a result of under-coordinated atoms being present close to the defect. This study focuses on the potential application of defective aluminum nitride nanosheets (AlNNS) in supercapacitors by examining their quantum capacitance properties. We verified the structural integrity of the primitive cell using cohesive energy calculations and phonon spectrum analysis. According to our findings, thin monolayers with deficiencies in nitrogen (N), aluminum (Al), or Al–N exhibit either metallic or narrow-bandgap semiconducting behaviour. Calculations of defect formation energy indicate that N-deficient AlNNS is the optimal option. The presence of under-coordinated atoms near the defect leads to the formation of new impurity states around the Fermi level.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"135 - 142"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865792","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":"Cosmological Bounce Horizon from First Principles: FRG-Derived Resolution of Spacetime Singularities via the Relativistic Zero Point","authors":"Abdul Sahib Machi García","doi":"10.1134/S1063776125601776","DOIUrl":"10.1134/S1063776125601776","url":null,"abstract":"<p>A renormalization-group mechanism for the resolution of spacetime singularities is formulated on the basis of the Relativistic Zero Point (RZP) principle. The quantum vacuum is modeled as a geometric medium described by an order parameter Θ, whose flow is constrained by Functional Renormalization Group (FRG) equations. A scalar-tensor truncation yields a non-Gaussian fixed point (NGFP) with parameters <span>(xi approx 0.65)</span>, <span>({{lambda }_{*}} approx 0.42)</span>, and <span>({{nu }_{*}} approx 1.00)</span>. The resulting transition <span>(Theta to {{nu }_{*}})</span> replaces classical divergences with a smooth bounce horizon. The formulation consolidates previous developments [1, 2] and integrates the scalar-tensor RZP construction [3]. Phenomenological predictions include a tensor-to-scalar ratio <span>(r sim 0.025)</span>, a gravitational-wave dispersion scale <span>(epsilon sim 8.3 times {{10}^{{ - 8}}})</span>, and expected post-merger echo delays of order <span>(Delta t sim 4.2)</span> ms.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"97 - 100"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865788","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":"The Special Theory of Relativity in Six Dimensions of Spacetime Continuum","authors":"Chandra Bahadur Khadka","doi":"10.1134/S106377612560206X","DOIUrl":"10.1134/S106377612560206X","url":null,"abstract":"<p>In this work we extend the four-dimensional space time theory of special relativity to six dimensions by adding two extra time coordinates, thereby we propose here six Lorentz transformation equations between inertial frames of reference moving in the three dimensions of space. The Lorentz matrix of order 6 × 6 using new six transformation equations is presented for the case when the coordinate systems have a relative velocity in three dimensions. Also, an elementary derivation of the new transformations in terms of hyperbolic functions including its matrix formulation has been thoroughly discussed. In addition to these, the invariance of differential space-time interval, invariance of d’Alembert operator, transformation of energy and momentum have been theoretically interpreted on the basis of the extended Lorentz transformation equations.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"107 - 134"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865791","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":"Third Harmonic Generation of Cosh-Gaussian Laser Beam in Unmagnetized Plasma: Role of Relativistic and Ponderomotive Nonlinearity","authors":"Keshav Walia,&nbsp;Taranjot Singh","doi":"10.1134/S1063776125602095","DOIUrl":"10.1134/S1063776125602095","url":null,"abstract":"<p>The present study focuses on third harmonic generation (THG) of cosh-Gaussian laser beam propagating through unmagnetized plasma, taking in to account joint influence of relativistic and ponderomotive (RP) nonlinearities. The joint action of RP force drives electron redistribution, resulting in plasma density fluctuations, which in turn excite electron plasma waves (EPW) at twice the fundamental frequency through <span>({{vec {text{V}}}} times {{vec {text{B}}}})</span> force. The nonlinear coupling of excited EPW with fundamental beam produces THG. A nonlinear differential equation governing evolution of beam waist of fundamental beam along with expression for third harmonic conversion efficiency are derived by using WKB approximation in conjugation with paraxial theory. The study further explores influence of laser and plasma parameters as well as RP force on self-focusing behavior of fundamental beam and THG conversion efficiency, providing comprehensive insight in to nonlinear laser plasma interaction for structured cosh-Gaussian beams.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"143 - 151"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865794","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":"Electrically Tunable Linear Dichroism in Graphene Nanoribbon-Based Metasurfaces for Controlling the Polarization of Terahertz Radiation","authors":"G. S. Makeeva,&nbsp;M. S. Nikitin","doi":"10.1134/S1063776126700020","DOIUrl":"10.1134/S1063776126700020","url":null,"abstract":"&lt;p&gt;&lt;i&gt;Background.&lt;/i&gt; The aim of this work is a numerical investigation of linear dichroism in graphene nanoribbon (GNR) metasurfaces in transmission, reflection, and absorption regimes in the terahertz (THz) frequency range as an important property for controlling and characterizing polarization in THz devices based on them, which are dynamically tunable by gating the chemical potential of graphene (by applying an electric field). &lt;i&gt;Materials and methods.&lt;/i&gt; An effective way to achieve dynamic dichroism control is the integration of 2D materials (including graphene) into metasurfaces. Their surface conductivity ensures dynamic control over a broad THz frequency band using electrical biasing or chemical doping. Surface plasmon polaritons in graphene exhibit high spatial localization and ensure the manipulation of THz radiation at extreme nanoscales. A numerical investigation of dichroism in GNR metasurfaces has been performed based on automated modeling methods by using the CST Microwave Studio software. The Floquet channel method has been chosen to solve the electrodynamic problem of diffraction of linearly polarized plane waves with the &lt;i&gt;p&lt;/i&gt;‑ and &lt;i&gt;s&lt;/i&gt;-polarization on a GNR metasurface. The boundary value problem of electrodynamics in CST MWS is solved using the numerical finite element method (FEM) in the frequency domain. &lt;i&gt;Results.&lt;/i&gt; The spectral dependences of the transmission, reflection, and absorption coefficients of linearly polarized normally and obliquely incident &lt;i&gt;p&lt;/i&gt;- and &lt;i&gt;s&lt;/i&gt;-polarized plane waves on a GNR metasurface have been calculated for different values of chemical potential µ&lt;sub&gt;c&lt;/sub&gt; and wave incidence angle α in the THz frequency range. The spectral dependences of the linear dichroism coefficients (LDC) of the GNR metasurface have been calculated in the absorption, transmission, and reflection regimes, and analysis of the dichroism controllability has been performed with varying chemical potential µ&lt;sub&gt;c&lt;/sub&gt; (0.2–1 eV) and wave incidence angle α (from 0° to 80°) in the THz range. &lt;i&gt;Conclusions.&lt;/i&gt; The numerical investigation results show that the LDC maxima are attained at the resonant frequencies of the graphene metasurface. The resonant frequencies and the LDC magnitude are controlled by varying the chemical potential µ&lt;sub&gt;сh&lt;/sub&gt; of graphene; with increasing µ&lt;sub&gt;c&lt;/sub&gt; (0.2–1 eV), the LDC increases. By varying the chemical potential (in the range of µ&lt;sub&gt;с&lt;/sub&gt; = 0.2–1 eV), it is possible to tune (for the given geometric parameters of the metasurface (period &lt;i&gt;d&lt;/i&gt; = 1 μm) based on a GNR (width &lt;i&gt;w&lt;/i&gt; = 0.5 μm)) the LDC function in the range of 0.37–0.52 in the frequency range of 7.24–16.58 THz (at normal incidence). The linear dichroism coefficient depends on incidence angle α and reaches a maximum value of LDC = 0.56 at oblique incidence (α = 80°) at frequency &lt;i&gt;f&lt;/i&gt;&lt;sub&gt;res&lt;/sub&gt; = 7.6 THz and µ&lt;sub&gt;с&lt;/sub&gt; = 0.2 eV. GNR metasurfaces exhibit polarization modulation and polariz","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"188 - 196"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865789","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":"An Entropic Vacuum Curvature Model Producing Dark-Matter-Like Effects","authors":"T. S. Taylor","doi":"10.1134/S1063776126600194","DOIUrl":"10.1134/S1063776126600194","url":null,"abstract":"<p>We present a cosmological framework in which spacetime curvature, the arrow of time, and cosmic acceleration arise from a single scalar entropy field <span>(mathcal{S}({{x}^{mu }}))</span> defined as the logarithm of the local quantum partition function. Within this formulation, observable quantities emerge from derivatives of <span>(mathcal{S})</span>: first derivatives encode energy flow and temporal directionality, while second derivatives generate spacetime curvature. Residual, non-equilibrium excitations of the entropy field above a renormalized vacuum baseline give rise to an effective curvature that reproduces key phenomenological features commonly attributed to dark energy and dark matter. On cosmological scales, a nearly homogeneous but nonzero second derivative of <span>(mathcal{S})</span> yields a de Sitter geometry, with the observed cosmological constant arising from dimensional scaling between the Planck length and the asymptotic de Sitter curvature radius. This geometric interpretation naturally accounts for the 10¹²²-order suppression between naive quantum zero-point energy estimates and the measured value of <span>(Lambda )</span> without invoking fine-tuned cancellations. On astrophysical scales, localized variations of the entropy field act as additional effective sources of curvature, reproducing galactic dynamics and gravitational lensing behavior typically modeled with dark matter. Regions of negative entropic curvature correspond to the geometric conditions required for exotic general-relativistic metrics such as warp bubbles and traversable wormholes. At laboratory scales, the Casimir effect emerges as a boundary-induced perturbation of the entropy field, providing an experimentally accessible manifestation of the same underlying mechanism. This work does not seek to invalidate the empirical successes of <span>(Lambda )</span>CDM, but instead proposes an effective geometric interpretation of dark-matter-like gravitational behavior arising from an entropic vacuum residual. In appropriate limits, standard cosmological expansion histories are recovered. In this sense, dark-matter-like gravitational behavior emerges as a coarse-grained geometric response of the entropic vacuum residual. Taken together, these results support a picture in which spacetime geometry, temporal flow, and gravitational phenomena arise as emergent, coarse-grained responses of an underlying entropic field, offering a unified informational perspective on gravity across scales.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"197 - 217"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865744","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":"Calculation of Characteristics of a Pulsed Electrojet Engine under the Variation of Energy Accumulator Parameters","authors":"V. V. Kuzenov,&nbsp;S. V. Ryzhkov","doi":"10.1134/S1063776126700019","DOIUrl":"10.1134/S1063776126700019","url":null,"abstract":"<p>In this article, we investigate the physicotechnical processes occurring in the gas-discharge chamber of a low-pressure radio-frequency (RF) helicon-type discharge, as well as in a coaxial magnetoplasma accelerator operating on its basis. Using the formulated mathematical model (of an RF source and a plasma accelerator), we analyze the effect of variation of the engine parameter on its working characteristics.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"178 - 187"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865787","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":"Hydrodynamic Instability of the “Reverse Flow” in a Lyotropic Nematic","authors":"A. V. Golovanov","doi":"10.1134/S1063776125601995","DOIUrl":"10.1134/S1063776125601995","url":null,"abstract":"<p>A model is proposed for the domain structure formed in a layer of a nematic (lyotropic liquid crystal) during its reorientation from a conditionally planar state to the homeotropic state under the action of boundaries in zero external electric and magnetic fields in the absence of mechanical deformations. The model is based on the effect of “reverse flow,” viz., a change in the director orientation, which leads to the motion of the centers of mass of nematic molecules and ultimately to a nematic flow with a nonzero velocity gradient. The results of modeling are compared with experimental data on the observation of domain structures in a lyotropic nematic of the disulfoindanthrone–water system. It is shows that the proposed model provides a satisfactory description of the experimental results.</p>","PeriodicalId":629,"journal":{"name":"Journal of Experimental and Theoretical Physics","volume":"142 2","pages":"101 - 106"},"PeriodicalIF":0.8,"publicationDate":"2026-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147865790","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}