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Search Results (2,108)

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Journal = Symmetry
Section = Physics

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4 pages, 171 KiB  
Editorial
Special Issue: Electron Diffraction and Structural Imaging—Volume I
by Partha Pratim Das, Arturo Ponce-Pedraza, Enrico Mugnaioli and Stavros Nicolopoulos
Symmetry 2025, 17(8), 1288; https://doi.org/10.3390/sym17081288 - 11 Aug 2025
Abstract
In recent years, electron diffraction (ED) and structural imaging have undergone a major resurgence in the scientific community, driven by continuous advancements in transmission electron microscopy (TEM) instrumentation, such as Cs correctors, direct detection cameras and automation, and the development or expansion of [...] Read more.
In recent years, electron diffraction (ED) and structural imaging have undergone a major resurgence in the scientific community, driven by continuous advancements in transmission electron microscopy (TEM) instrumentation, such as Cs correctors, direct detection cameras and automation, and the development or expansion of analytical methods, such as cryo-EM, beam precession, 4D Scanning Electron Diffraction, 3D electron diffraction, 4D-STEM, and ptychography [...] Full article
(This article belongs to the Special Issue Electron Diffraction and Structural Imaging)
4 pages, 172 KiB  
Editorial
Special Issue: Electron Diffraction and Structural Imaging—Volume II
by Partha Pratim Das, Arturo Ponce-Pedraza, Enrico Mugnaioli and Stavros Nicolopoulos
Symmetry 2025, 17(8), 1287; https://doi.org/10.3390/sym17081287 - 11 Aug 2025
Abstract
Following the success of the first edition of our Special Issue “Electron Diffraction and Structural Imaging”, we present Volume II, featuring new and innovative contributions that further expand the scope and depth of this rapidly evolving field [...] Full article
(This article belongs to the Special Issue Electron Diffraction and Structural Imaging II)
20 pages, 1554 KiB  
Article
Structure of Odd-A Ag Isotopes Studied via Algebraic Approaches
by Stanimir Kisyov and Stefan Lalkovski
Symmetry 2025, 17(8), 1276; https://doi.org/10.3390/sym17081276 - 8 Aug 2025
Viewed by 75
Abstract
The structure of the odd-A silver isotopes Ag103115 is discussed within the frame of the interacting boson–fermion model (IBFM). An overview of their key properties is presented, with a particular attention paid to the “J-1 anomaly”, represented [...] Read more.
The structure of the odd-A silver isotopes Ag103115 is discussed within the frame of the interacting boson–fermion model (IBFM). An overview of their key properties is presented, with a particular attention paid to the “J-1 anomaly”, represented by an abnormal ordering of the lowest 7/2+ and 9/2+ states. By examining previously published data and newly performed calculations, it is demonstrated that the experimentally known level schemes and electromagnetic properties of Ag103115 can be reproduced well within IBFM-1 by using a consistent set of model parameters. The contribution of different single-particle orbitals to the structure of the lowest-lying excited nuclear states in Ag103115 is discussed. Given that the J-1 anomaly brings down the 7/2+ level from the j3 multiplet to energies, which can be thermally populated in hot stellar environments, the importance of low-lying excited states in odd-A silver isotopes for astrophysical processes is outlined. Full article
(This article belongs to the Special Issue Feature Papers in 'Physics' Section 2025)
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29 pages, 4460 KiB  
Article
Dimensional and Numerical Approach to Heat Transfer in Structural Elements with a Symmetrical Cross Section
by Betti Bolló, Ioan Száva, Ildikó-Renáta Száva, Teofil-Florin Gălățanu, Károly Jármai and Denisa-Elena Muntean
Symmetry 2025, 17(8), 1271; https://doi.org/10.3390/sym17081271 - 8 Aug 2025
Viewed by 201
Abstract
The structures of buildings employ elements with symmetrical cross sections (columns have two axes of symmetry, and connecting beams have at least one), leading to symmetrical states of stress and deformation under the action of mechanical and thermal loads. Thermal stresses, resulting from [...] Read more.
The structures of buildings employ elements with symmetrical cross sections (columns have two axes of symmetry, and connecting beams have at least one), leading to symmetrical states of stress and deformation under the action of mechanical and thermal loads. Thermal stresses, resulting from temperature variations and fires, must be taken into account during calculations. Thus, it is important to perform theoretical and experimental studies on the propagation of heat flux during fires. Experimental investigations on prototypes can be replaced by investigations into attached, reduced-scale models. With the help of the model law (ML), deduced by dimensional approaches, the results obtained by the model can be extrapolated to the prototype. In the present article, the Szirtes’ Modern Dimensional Analysis (MDA) method is proposed; this is a simple, reliable, and repeatable dimensional approach. By applying the MDA to both the structural elements and model of an entire industrial hall, in terms of thermal field propagation, the authors demonstrate the undeniable effectiveness of the method in these construction calculations. MDA enables the efficient and easy analysis of thermal states of the homologous points of the prototype, even for spatial structures. Full article
(This article belongs to the Section Physics)
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8 pages, 342 KiB  
Article
Should the Evolution of Our Universe Be Treated as an Initial Value Problem?
by Martin Tamm
Symmetry 2025, 17(8), 1258; https://doi.org/10.3390/sym17081258 - 7 Aug 2025
Viewed by 143
Abstract
In classical physics, the traditional way to handle dynamics is to work with initial value problems: Specifying all variables and their time-derivatives at a certain time will, together with the equations of motion, give the state of the system at any time. In [...] Read more.
In classical physics, the traditional way to handle dynamics is to work with initial value problems: Specifying all variables and their time-derivatives at a certain time will, together with the equations of motion, give the state of the system at any time. In this paper, it is questioned whether this is the right way to treat cosmology. The main reason is that cosmology, as opposed to almost all other parts of physics, deals with genuinely global problems. The main example in this paper will be the accelerating expansion. It is not claimed that the model studied here gives any kind of final explanation of this phenomenon. Nevertheless, it shows that what is commonly interpreted as the result of some dark energy, could instead be the result of a global condition for the universe. This model cannot be treated as a classical initial value problem. But an interesting additional property is that it can explain why the rate of acceleration now seems to be decreasing with time. Full article
(This article belongs to the Special Issue Feature Papers in 'Physics' Section 2025)
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16 pages, 457 KiB  
Article
Examples for BPS Solitons Destabilized by Quantum Effects
by Willem J. Meyer and Herbert Weigel
Symmetry 2025, 17(8), 1229; https://doi.org/10.3390/sym17081229 - 4 Aug 2025
Viewed by 123
Abstract
We investigate serval models for two scalar fields in one space dimension with topologically stable solitons that are constructed from BPS equations. The asymptotic behavior of these solitons fully determines their classical energies. A particular feature of the considered models is that there [...] Read more.
We investigate serval models for two scalar fields in one space dimension with topologically stable solitons that are constructed from BPS equations. The asymptotic behavior of these solitons fully determines their classical energies. A particular feature of the considered models is that there are several translationally invariant ground states that we call primary and secondary vacua. The former are those that are asymptotically assumed by the solitons. Solitons that occupy a secondary vacuum in finite but eventually large portions of space are classically degenerate. Thus the quantum contributions to the energies are decisive for the energetically favored soliton. While some of these solitons were constructed previously, we, for the first time, compute the leading (one-loop) quantum contribution their energies. In all cases considered we find that this contribution is not bounded from below and that it is the more negative the larger the region is in which the soliton approaches a secondary vacuum. This corroborates the conjecture, earlier inferred from the Shifman-Voloshin soliton, that the availability of secondary vacua destabilizes these solitons on the quantum level. Full article
(This article belongs to the Section Physics)
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22 pages, 1287 KiB  
Article
Comparative Analysis of the Gardner Equation in Plasma Physics Using Analytical and Neural Network Methods
by Zain Majeed, Adil Jhangeer, F. M. Mahomed, Hassan Almusawa and F. D. Zaman
Symmetry 2025, 17(8), 1218; https://doi.org/10.3390/sym17081218 - 1 Aug 2025
Viewed by 189
Abstract
In the present paper, a mathematical analysis of the Gardner equation with varying coefficients has been performed to give a more realistic model of physical phenomena, especially in regards to plasma physics. First, a Lie symmetry analysis was carried out, as a result [...] Read more.
In the present paper, a mathematical analysis of the Gardner equation with varying coefficients has been performed to give a more realistic model of physical phenomena, especially in regards to plasma physics. First, a Lie symmetry analysis was carried out, as a result of which a symmetry classification following the different representations of the variable coefficients was systematically derived. The reduced ordinary differential equation obtained is solved using the power-series method and solutions to the equation are represented graphically to give an idea of their dynamical behavior. Moreover, a fully connected neural network has been included as an efficient computation method to deal with the complexity of the reduced equation, by using traveling-wave transformation. The validity and correctness of the solutions provided by the neural networks have been rigorously tested and the solutions provided by the neural networks have been thoroughly compared with those generated by the Runge–Kutta method, which is a conventional and well-recognized numerical method. The impact of a variation in the loss function of different coefficients has also been discussed, and it has also been found that the dispersive coefficient affects the convergence rate of the loss contribution considerably compared to the other coefficients. The results of the current work can be used to improve knowledge on the nonlinear dynamics of waves in plasma physics. They also show how efficient it is to combine the approaches, which consists in the use of analytical and semi-analytical methods and methods based on neural networks, to solve nonlinear differential equations with variable coefficients of a complex nature. Full article
(This article belongs to the Section Physics)
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27 pages, 6143 KiB  
Article
Optical Character Recognition Method Based on YOLO Positioning and Intersection Ratio Filtering
by Kai Cui, Qingpo Xu, Yabin Ding, Jiangping Mei, Ying He and Haitao Liu
Symmetry 2025, 17(8), 1198; https://doi.org/10.3390/sym17081198 - 27 Jul 2025
Viewed by 291
Abstract
Driven by the rapid development of e-commerce and intelligent logistics, the volume of express delivery services has surged, making the efficient and accurate identification of shipping information a core requirement for automatic sorting systems. However, traditional Optical Character Recognition (OCR) technology struggles to [...] Read more.
Driven by the rapid development of e-commerce and intelligent logistics, the volume of express delivery services has surged, making the efficient and accurate identification of shipping information a core requirement for automatic sorting systems. However, traditional Optical Character Recognition (OCR) technology struggles to meet the accuracy and real-time demands of complex logistics scenarios due to challenges such as image distortion, uneven illumination, and field overlap. This paper proposes a three-level collaborative recognition method based on deep learning that facilitates structured information extraction through regional normalization, dual-path parallel extraction, and a dynamic matching mechanism. First, the geometric distortion associated with contour detection and the lightweight direction classification model has been improved. Second, by integrating the enhanced YOLOv5s for key area localization with the upgraded PaddleOCR for full-text character extraction, a dual-path parallel architecture for positioning and recognition has been constructed. Finally, a dynamic space–semantic joint matching module has been designed that incorporates anti-offset IoU metrics and hierarchical semantic regularization constraints, thereby enhancing matching robustness through density-adaptive weight adjustment. Experimental results indicate that the accuracy of this method on a self-constructed dataset is 89.5%, with an F1 score of 90.1%, representing a 24.2% improvement over traditional OCR methods. The dynamic matching mechanism elevates the average accuracy of YOLOv5s from 78.5% to 89.7%, surpassing the Faster R-CNN benchmark model while maintaining a real-time processing efficiency of 76 FPS. This study offers a lightweight and highly robust solution for the efficient extraction of order information in complex logistics scenarios, significantly advancing the intelligent upgrading of sorting systems. Full article
(This article belongs to the Section Physics)
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14 pages, 4107 KiB  
Article
Thermal Influence on Chirality-Driven Dynamics and Pinning of Transverse Domain Walls in Z-Junction Magnetic Nanowires
by Mohammed Al Bahri, Salim Al-Kamiyani, Mohammed M. Al Hinaai and Nisar Ali
Symmetry 2025, 17(8), 1184; https://doi.org/10.3390/sym17081184 - 24 Jul 2025
Viewed by 247
Abstract
Magnetic nanowires with domain walls (DWs) play a crucial role in the advancement of next-generation memory and spintronic devices. Understanding the thermal effects on domain wall behavior is essential for optimizing performance and stability. This study investigates the thermal chirality-dependent dynamics and pinning [...] Read more.
Magnetic nanowires with domain walls (DWs) play a crucial role in the advancement of next-generation memory and spintronic devices. Understanding the thermal effects on domain wall behavior is essential for optimizing performance and stability. This study investigates the thermal chirality-dependent dynamics and pinning of transverse domain walls (TDWs) in Z-junction nanowires using micromagnetic simulations. The analysis focuses on head-to-head (HHW) and tail-to-tail (TTW) domain walls with up and down chirality under varying thermal conditions. The results indicate that higher temperatures reduce the pinning strength and depinning current density, leading to enhanced domain wall velocity. At 200 K, the HHWdown domain wall depins at a critical current density of 1.2 × 1011 A/m2, while HHWup requires a higher depinning temperature, indicating stronger pinning effects. Similarly, the depinning temperature (Td) increases with Z-junction depth (d), reaching 300 K at d = 50 nm, while increasing Z-junction (λ) weakens pinning, reducing Td to 150 K at λ = 50 nm. Additionally, the influence of Z-junction geometry and magnetic properties, such as saturation magnetization (Ms) and anisotropy constant (Ku), is examined to determine their effects on thermal pinning and depinning. These findings highlight the critical role of chirality and thermal activation in domain wall motion, offering insights into the design of energy-efficient, high-speed nanowire-based memory devices. Full article
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7 pages, 200 KiB  
Editorial
Topological Objects in Ordered Electronic Systems
by Serguei Brazovskii and Natasha Kirova
Symmetry 2025, 17(8), 1174; https://doi.org/10.3390/sym17081174 - 23 Jul 2025
Viewed by 213
Abstract
Most of correlated electronic systems possess ground states with broken crystal symmetries [...] Full article
(This article belongs to the Special Issue Topological Objects in Correlated Electronic Systems)
53 pages, 560 KiB  
Review
Notes on Derived Deformation Theory for Field Theories and Their Symmetries
by Ingmar Saberi
Symmetry 2025, 17(8), 1172; https://doi.org/10.3390/sym17081172 - 22 Jul 2025
Viewed by 294
Abstract
These notes are an informal overview of techniques related to deformation theory in the context of physics. Beginning from motivation for the concept of a sheaf, they build up through derived functors, resolutions, and the functor of points to the notion of a [...] Read more.
These notes are an informal overview of techniques related to deformation theory in the context of physics. Beginning from motivation for the concept of a sheaf, they build up through derived functors, resolutions, and the functor of points to the notion of a moduli problem, emphasizing physical motivation and the principles of locality and general covariance at each step. They are primarily aimed at those who have some prior exposure to quantum field theory and are interested in acquiring some intuition or orientation regarding modern mathematical methods. A couple of small things are new, including a discussion of the twist of N=1 conformal supergravity in generic backgrounds at the level of the component fields and a computation relating the two-dimensional local cocycle for the Weyl anomaly to the one for the Virasoro anomaly. I hope they will serve as a useful appetizer for the more careful and complete treatments of this material that are already available. Full article
(This article belongs to the Special Issue Symmetries, and Symmetry Breaking in String Theory)
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19 pages, 431 KiB  
Article
The Detection of a Defect in a Dual-Coupling Optomechanical System
by Zhen Li and Ya-Feng Jiao
Symmetry 2025, 17(7), 1166; https://doi.org/10.3390/sym17071166 - 21 Jul 2025
Viewed by 253
Abstract
We provide an approach to detect a nitrogen-vacancy (NV) center, which might be a defect in a diamond nanomembrane, using a dual-coupling optomechanical system. The NV center modifies the energy-level structure of a dual-coupling optomechanical system through dressed states arising from its interaction [...] Read more.
We provide an approach to detect a nitrogen-vacancy (NV) center, which might be a defect in a diamond nanomembrane, using a dual-coupling optomechanical system. The NV center modifies the energy-level structure of a dual-coupling optomechanical system through dressed states arising from its interaction with the mechanical membrane. Thus, we study the photon blockade in the cavity of a dual-coupling optomechanical system in which an NV center is embedded in a single-crystal diamond nanomembrane. The NV center significantly influences the statistical properties of the cavity field. We systematically investigate how three key NV center parameters affect photon blockade: (i) its coupling strength to the mechanical membrane, (ii) transition frequency, and (iii) decay rate. We find that the NV center can shift, give rise to a new dip, and even suppress the original dip in a bare quadratic optomechanical system. In addition, we can amplify the effect of the NV center on photon statistics by adding a gravitational potential when the NV center has little effect on photon blockade. Therefore, our study provides a method to detect diamond nanomembrane defects in a dual-coupling optomechanical system. Full article
(This article belongs to the Section Physics)
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38 pages, 4803 KiB  
Review
Charge Density Waves in Solids—From First Concepts to Modern Insights
by Danko Radić
Symmetry 2025, 17(7), 1135; https://doi.org/10.3390/sym17071135 - 15 Jul 2025
Viewed by 581
Abstract
We present a brief overview of the field of charge density waves (CDW) in condensed systems with focus set to the underlying mechanisms behind the CDW ground state. Our intention in this short review is not to count all related facts from the [...] Read more.
We present a brief overview of the field of charge density waves (CDW) in condensed systems with focus set to the underlying mechanisms behind the CDW ground state. Our intention in this short review is not to count all related facts from the vast volume of literature about this decades-old and still developing field, but rather to pinpoint the most important, mostly theoretical ones, presenting the development of the field. Starting from the “early days”, mainly based on weakly coupled, chain-like quasi-1D systems and Peierls instability, in which the Fermi surface nesting has been the predominant and practically paradigmatic mechanism of the CDW ground state stabilisation, we track the change in paradigms while entering the field of layered quasi-2D systems, with Fermi surface far away from the nesting regime, in which rather strong, essentially momentum-dependent interactions and particular reconstructions of the Fermi surface become essential. Examples of real quasi-1D materials, such as organic and inorganic conductors like Bechgaard salts or transition metal trichalcogenides and bronzes, in which experiment and theory have been extremely successful in providing detailed understanding, are contrasted to layered quasi-2D materials, such as high-Tc superconducting cuprates, intercalated graphite compounds or transition metal dichalcogenides, for which the theory explaining an onset of the CDWs constitutes a frontier of this fast-evolving field, strongly boosted by development of modern ab initio calculation methods. Full article
(This article belongs to the Section Physics)
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39 pages, 5065 KiB  
Review
Electroexcitation of Nucleon Resonances and Emergence of Hadron Mass
by Patrick Achenbach, Daniel S. Carman, Ralf W. Gothe, Kyungseon Joo, Victor I. Mokeev and Craig D. Roberts
Symmetry 2025, 17(7), 1106; https://doi.org/10.3390/sym17071106 - 9 Jul 2025
Viewed by 306
Abstract
Developing an understanding of phenomena driven by the emergence of hadron mass (EHM) is one of the most challenging problems in the Standard Model. This discussion focuses on the impact of results on nucleon resonance (N*) electroexcitation amplitudes (or [...] Read more.
Developing an understanding of phenomena driven by the emergence of hadron mass (EHM) is one of the most challenging problems in the Standard Model. This discussion focuses on the impact of results on nucleon resonance (N*) electroexcitation amplitudes (or γvpN* electrocouplings) obtained from experiments during the 6 GeV era in Hall B at Jefferson Lab on understanding EHM. Analyzed using continuum Schwinger function methods (CSMs), these results have revealed new pathways for the elucidation of EHM. A good description of the Δ(1232)3/2+, N(1440)1/2+, and Δ(1600)3/2+ electrocouplings, achieved by CSM analyses that express a realistic dressed quark mass function, sheds light on the strong interaction dynamics underlying EHM. Extensions to N* studies for higher-mass states are outlined, as well as experimental results anticipated in the 12 GeV era at Jefferson Lab and those that would be enabled by a further increase in the beam energy to 22 GeV. Full article
(This article belongs to the Special Issue The Symmetry of QCD Matter and Functional QCD Approaches)
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21 pages, 661 KiB  
Article
Semi-Analytical Solutions of the Rayleigh Oscillator Using Laplace–Adomian Decomposition and Homotopy Perturbation Methods: Insights into Symmetric and Asymmetric Dynamics
by Emad K. Jaradat, Omar Alomari, Audai A. Al-Zgool and Omar K. Jaradat
Symmetry 2025, 17(7), 1081; https://doi.org/10.3390/sym17071081 - 7 Jul 2025
Viewed by 256
Abstract
This study investigates the solution structure of the nonlinear Rayleigh oscillator equation through two widely used semi-analytical techniques: the Laplace–Adomian Decomposition Method (LADM) and the Homotopy Perturbation Method (HPM). The Rayleigh oscillator exhibits inherent asymmetry in its nonlinear damping term, which disrupts the [...] Read more.
This study investigates the solution structure of the nonlinear Rayleigh oscillator equation through two widely used semi-analytical techniques: the Laplace–Adomian Decomposition Method (LADM) and the Homotopy Perturbation Method (HPM). The Rayleigh oscillator exhibits inherent asymmetry in its nonlinear damping term, which disrupts the time-reversal symmetry present in linear oscillatory systems. Applying the LADM and HPM, we derive approximate solutions for the Rayleigh oscillator. Due to the absence of exact analytical solutions in the literature, these approximations are benchmarked against high-precision numerical results obtained using Mathematica’s NDSolve function. We perform a detailed error analysis across different damping parameter values ε and time intervals. Our results reveal how the asymmetric damping influences the accuracy and convergence behavior of each method. This study highlights the role of nonlinear asymmetry in shaping the solution dynamics and provides insight into the suitability of the LADM and HPM under varying conditions. Full article
(This article belongs to the Section Physics)
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