Physics and Symmetry Section: Feature Papers 2022

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 17560

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1. Information Media Center, Hiroshima University, 1-7-1, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8521, Japan
2. Core of Research for the Energetic Universe, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
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Dear Colleagues,

We are pleased to announce this new Special Issue on “Symmetry: Feature Papers 2022”. We aim to introduce new insights into science development or cutting-edge technology related to the physics and symmetry field, which are expected to make a great contribution to the community. The issue will cover topics, original research, and peer-reviewed articles related to the latest research and developments in any field of physics where symmetry plays a key role.

In general, this Special Issue will be a platform for researchers to publish their scientific work, helping them to influence the scientific community as well as the general public.

Prof. Dr. Tomohiro Inagaki
Dr. Olga Kodolova
Guest Editors

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Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (16 papers)

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Research

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17 pages, 2773 KiB  
Article
On the Effects of Tokamak Plasma Edge Symmetries on Turbulence Relaxation
by Nakia Carlevaro, Giovanni Montani and Fabio Moretti
Symmetry 2023, 15(9), 1745; https://doi.org/10.3390/sym15091745 - 11 Sep 2023
Viewed by 492
Abstract
The plasma edge of a tokamak configuration is characterized by turbulent dynamics leading to enhanced transport. We construct a simplified 3D Hasegawa–Wakatani model reducing to a single partial differential equation for the turbulent electric potential dynamics. Simulations demonstrate how the 3D turbulence relaxes [...] Read more.
The plasma edge of a tokamak configuration is characterized by turbulent dynamics leading to enhanced transport. We construct a simplified 3D Hasegawa–Wakatani model reducing to a single partial differential equation for the turbulent electric potential dynamics. Simulations demonstrate how the 3D turbulence relaxes on a 2D axisymmetric profile, corresponding to the so-called interchange turbulence. The spectral features of this regime are found to be strongly dependent on the initialization pattern. We outline that the emergence of axisymmetric turbulence is also achieved when the corresponding mode amplitude is not initialized. Then, we introduce the symmetries of the magnetic X-point of a tokamak configuration. We linearize the governing equation by treating the poloidal field as a small correction. We show that it is not always possible to solve the electric potential dynamics following a perturbative approach. This finding, which is due to resonance between the modes of the background and the poloidal perturbation, confirms that the X-point symmetries can alter the properties of turbulent transport in the edge region. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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32 pages, 882 KiB  
Article
Meson-Exchange Currents in Quasielastic Electron Scattering in a Generalized Superscaling Approach
by Paloma Rodriguez Casale, Jose Enrique Amaro and Maria B. Barbaro
Symmetry 2023, 15(9), 1709; https://doi.org/10.3390/sym15091709 - 06 Sep 2023
Cited by 2 | Viewed by 1031
Abstract
We introduce a method for consistently incorporating meson-exchange currents (MEC) within the superscaling analysis with relativistic effective mass, featuring a new scaling variable, ψ*, and single-nucleon cross-sections derived from the relativistic mean field (RMF) model of nuclear matter. The single-nucleon prefactor [...] Read more.
We introduce a method for consistently incorporating meson-exchange currents (MEC) within the superscaling analysis with relativistic effective mass, featuring a new scaling variable, ψ*, and single-nucleon cross-sections derived from the relativistic mean field (RMF) model of nuclear matter. The single-nucleon prefactor is obtained from the 1p1h matrix element of the one-body current, combined with the two-body current, averaged over a momentum distribution of Fermi kind. The approach is applied to selected quasielastic cross-sectional data on 12C. The results reveal a departure from scaling behavior, yet, intriguingly, the data collapse into a discernible band that is parametrized using a simple function of ψ*. This calculation, as developed, is not intended to provide pinpoint precision in extracting nuclear responses. Instead, it offers a global description of the quasielastic data with a considerable level of uncertainty. However, this approach effectively captures the overall trends of the quasielastic data beyond the Fermi gas model with a minimal number of parameters. The model incorporates partially transverse enhancement of the response, as embedded within the relativistic mean field framework. However, it does not account for enhancements attributed to the combined effects of tensor correlations and MEC, given that the initial RMF model lacks these correlations. A potential avenue for improvement involves starting with a correlated Fermi gas model to incorporate additional enhancements into single-nucleon responses. This study serves as a practical demonstration of implementing such corrections. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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22 pages, 5890 KiB  
Article
Large-Scale Asymmetry in the Distribution of Galaxy Spin Directions—Analysis and Reproduction
by Lior Shamir
Symmetry 2023, 15(9), 1704; https://doi.org/10.3390/sym15091704 - 06 Sep 2023
Cited by 2 | Viewed by 970
Abstract
Recent independent observations using several different telescope systems and analysis methods have provided evidence of parity violation between the numbers of galaxies that spin in opposite directions. On the other hand, other studies argue that no parity violation can be identified. This paper [...] Read more.
Recent independent observations using several different telescope systems and analysis methods have provided evidence of parity violation between the numbers of galaxies that spin in opposite directions. On the other hand, other studies argue that no parity violation can be identified. This paper provides detailed analysis, statistical inference, and reproduction of previous reports that show no preferred spin direction. Code and data used for the reproduction are publicly available. The results show that the data used in all of these studies agree with the observation of a preferred direction as observed from Earth. In some of these studies, the datasets were too small, or the statistical analysis was incomplete. In other papers, the results were impacted by experimental design decisions that led directly to showing nonpreferred direction. In some of these cases, these decisions were not stated in the papers but were revealed after further investigation in cases where the reproduction of the work did not match the results reported in the papers. These results show that the data used in all of these previous studies, in fact, agree with the contention that galaxies as observed from Earth have a preferred spin direction, and the distribution of galaxy spin directions as observed from Earth forms a cosmological-scale dipole axis. This study also shows that the reason for the observations is not necessarily an anomaly in the large-scale structure, and can also be related to internal structure of galaxies. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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13 pages, 981 KiB  
Article
Symmetric Phase Portraits of Homogeneous Polynomial Hamiltonian Systems of Degree 1, 2, 3, 4, and 5 with Finitely Many Equilibria
by Rebiha Benterki and Jaume Llibre
Symmetry 2023, 15(8), 1476; https://doi.org/10.3390/sym15081476 - 25 Jul 2023
Viewed by 629
Abstract
Roughly speaking, the Poincaré disc D2 is the closed disc centered at the origin of the coordinates of R2, where the whole of R2 is identified with the interior of D2 and the circle of the boundary of [...] Read more.
Roughly speaking, the Poincaré disc D2 is the closed disc centered at the origin of the coordinates of R2, where the whole of R2 is identified with the interior of D2 and the circle of the boundary of D2 is identified with the infinity of R2, because in the plane R2, we can go to infinity in as many directions as points have the circle. The phase portraits of the quadratic Hamiltonian systems in the Poincaré disc were classified in 1994. Since then, no new interesting classes of Hamiltonian systems have been classified on the Poincaré disc. In this paper, we determine the phase portraits in the Poincaré disc of five classes of homogeneous Hamiltonian polynomial differential systems of degrees 1, 2, 3, 4, and 5 with finitely many equilibria. Moreover, all these phase portraits are symmetric with respect to the origin of coordinates. We showed that these polynomial differential systems exhibit precisely 2, 2, 3, 3, and 4 topologically distinct phase portraits in the Poincaré disc. Of course, the new results are for the homogeneous Hamiltonian polynomial differential systems of degrees 3, 4, and 5. The tools used here for obtaining these phase portraits also work for obtaining any phase portrait of a homogeneous Hamiltonian polynomial differential system of arbitrary degree. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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22 pages, 388 KiB  
Article
Mirror Symmetry for New Physics beyond the Standard Model in 4D Spacetime
by Wanpeng Tan
Symmetry 2023, 15(7), 1415; https://doi.org/10.3390/sym15071415 - 14 Jul 2023
Cited by 2 | Viewed by 852
Abstract
The two discrete generators of the full Lorentz group O(1,3) in 4D spacetime are typically chosen to be parity inversion symmetry P and time reversal symmetry T, which are responsible for the four topologically separate components [...] Read more.
The two discrete generators of the full Lorentz group O(1,3) in 4D spacetime are typically chosen to be parity inversion symmetry P and time reversal symmetry T, which are responsible for the four topologically separate components of O(1,3). Under general considerations of quantum field theory (QFT) with internal degrees of freedom, mirror symmetry is a natural extension of P, while CP symmetry resembles T in spacetime. In particular, mirror symmetry is critical as it doubles the full Dirac fermion representation in QFT and essentially introduces a new sector of mirror particles. Its close connection to T-duality and Calabi–Yau mirror symmetry in string theory is clarified. Extension beyond the Standard Model can then be constructed using both left- and right-handed heterotic strings guided by mirror symmetry. Many important implications such as supersymmetry, chiral anomalies, topological transitions, Higgs, neutrinos, and dark energy are discussed. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
19 pages, 327 KiB  
Article
An Evolving Spacetime Metric Induced by a ‘Static’ Source
by Martin Land
Symmetry 2023, 15(7), 1381; https://doi.org/10.3390/sym15071381 - 07 Jul 2023
Viewed by 669
Abstract
In a series of recent papers we developed a formulation of general relativity in which spacetime and the dynamics of matter evolve with a Poincaré invariant parameter τ. In this paper, we apply the formalism to derive the metric induced by a [...] Read more.
In a series of recent papers we developed a formulation of general relativity in which spacetime and the dynamics of matter evolve with a Poincaré invariant parameter τ. In this paper, we apply the formalism to derive the metric induced by a ‘static’ event evolving uniformly along its t-axis at the spatial origin x=0. The metric is shown to vary with t and τ, as well as spatial distance r, taking its maximum value for a test particle at the retarded time τ=tr/c. In the resulting picture, an event localized in space and time produces a metric field similarly localized, where both evolve in τ. We first derive this metric as a solution to the wave equation in linearized field theory, and discuss its limitations by studying the geodesic motion it produces for an evolving event. By then examining this solution in the 4+1 formalism, which poses an initial value problem for the metric under τ-evolution, we clarify these limitations and indicate how they may be overcome in a solution to the full nonlinear field equations. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
17 pages, 524 KiB  
Article
Chandrasekhar Mass Limit of White Dwarfs in Modified Gravity
by Artyom V. Astashenok, Sergey D. Odintsov and Vasilis K. Oikonomou
Symmetry 2023, 15(6), 1141; https://doi.org/10.3390/sym15061141 - 24 May 2023
Cited by 12 | Viewed by 1294
Abstract
We investigate the Chandrasekhar mass limit of white dwarfs in various models of f(R) gravity. Two equations of state for stellar matter are used: the simple relativistic polytropic equation with polytropic index n=3 and the realistic Chandrasekhar equation [...] Read more.
We investigate the Chandrasekhar mass limit of white dwarfs in various models of f(R) gravity. Two equations of state for stellar matter are used: the simple relativistic polytropic equation with polytropic index n=3 and the realistic Chandrasekhar equation of state. For calculations, it is convenient to use the equivalent scalar–tensor theory in the Einstein frame and then to return to the Jordan frame picture. For white dwarfs, we can neglect terms containing relativistic effects from General Relativity and we consider the reduced system of equations. Its solution for any model of f(R)=R+βRm (m2, β>0) gravity leads to the conclusion that the stellar mass decreases in comparison with standard General Relativity. For realistic equations of state, we find that there is a value of the central density for which the mass of a white dwarf peaks. Therefore, in frames of modified gravity, there is a lower limit on the radius of stable white dwarfs, and this minimal radius is greater than in General Relativity. We also investigate the behavior of the Chandrasekhar mass limit in f(R) gravity. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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15 pages, 483 KiB  
Article
Viability of Baryon to Entropy Ratio in Modified Hořava–Lifshitz Gravity
by Abdul Jawad, Abdul Malik Sultan and Shamaila Rani
Symmetry 2023, 15(4), 824; https://doi.org/10.3390/sym15040824 - 29 Mar 2023
Cited by 2 | Viewed by 1147
Abstract
In this paper, we study the matter–antimatter imbalance in the universe through baryogenesis (also known as baryosynthesis), which is a physical process that took off just a little while after the big bang explosion, producing a supremacy of matter over antimatter. In this [...] Read more.
In this paper, we study the matter–antimatter imbalance in the universe through baryogenesis (also known as baryosynthesis), which is a physical process that took off just a little while after the big bang explosion, producing a supremacy of matter over antimatter. In this work, we commit the reproduction of the baryon to entropy ratio (ηBS=ηβηβ¯S), where ηβ(ηβ¯) is a baryon(anti-baryon) number and S is the entropy of the universe in the presence of modified Hořava-Lifshitz F(R) gravity, which is also called F(R˜)-gravity. We inspect different baryogenesis interactions proportional to R˜ (where R˜ is the argument of general function F used for the development of modified Hořava-Lifshitz gravity). For this study, we examine two models by choosing different values of F(R˜). In the first model, the functional value of F(R˜)=R˜+αR˜2 (where α is a real constant). The second model is more generalized and extended as compare to first one. Mathematically, this model is given by F(R˜)=R˜+αR˜2+βR˜m, where α, β are real constants and m>2 is a real model parameter. Our results for both models and different values of m point out that matter-antimatter asymmetry does not vanish under the effect of the modified Hořava-Lifshitz theory of gravity, which shows a consistent and compatible fact of gravitational baryogenesis with recent observational data. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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15 pages, 50245 KiB  
Article
The Effects of Reduced Gravity and Radiative Heat Transfer on the Magnetohydrodynamic Flow Past a Non-Rotating Stationary Sphere Surrounded by a Porous Medium
by Amir Abbas, Ioannis E. Sarris, Muhammad Ashraf, Kaouther Ghachem, Nidhal Hnaien and Badr M. Alshammari
Symmetry 2023, 15(4), 806; https://doi.org/10.3390/sym15040806 - 26 Mar 2023
Cited by 13 | Viewed by 1140
Abstract
In the present study, the effects of reduced gravity and solar radiation on the magnetohydrodynamics (MHD) fluid flow and heat transfer past a solid and stationary sphere embedded in a porous medium are investigated. A model describing the considered configuration is put in [...] Read more.
In the present study, the effects of reduced gravity and solar radiation on the magnetohydrodynamics (MHD) fluid flow and heat transfer past a solid and stationary sphere embedded in a porous medium are investigated. A model describing the considered configuration is put in dimensionless form using appropriate dimensionless variables and then transformed to primitive form for a smooth algorithm on a computing tool. A primitive form of the model is solved by employing the finite difference method. Solutions for variables of interest, such as velocity distribution and temperature field, along with their gradients, are depicted in graphs and tables. The main goal of the paper is to study the physical impact of reduced gravity on heat transfer and fluid flow around a sphere surface inserted in a porous medium in the presence of an applied magnetic field and solar radiation. The effects of the governing parameters, which are the reduced gravity parameter, magnetic field parameter, radiation parameter, porous medium parameter, and the Prandtl number, are discussed and physically interpreted. The displayed solutions indicate that velocity rises with the reduced gravity and solar radiation parameters but decreases with augmenting the Prandtl number, magnetic field parameter, and porous medium parameter. It is deduced from the presented results that the temperature becomes lower by increasing the values of the reduced gravity parameter and the Prandtl number, but, on the other hand, it becomes higher by increasing the values of the magnetic field, the porous medium, and the radiation parameters at all the considered positions of the surface of the sphere. A comparison between the present and already published results is performed to check the validity of the proposed numerical model. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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16 pages, 6468 KiB  
Article
Study of Propeller Vortex Characteristics under Loading Conditions
by Jiawei Yu, Bo Zhou, Hui Liu, Xiaoshuang Han, Guobiao Hu and Teng Zhang
Symmetry 2023, 15(2), 445; https://doi.org/10.3390/sym15020445 - 07 Feb 2023
Viewed by 1738
Abstract
Marine load is an important factor affecting propeller propulsion efficiency, and the study of the wake evolution mechanism under different conditions is an essential part of the propeller equipment design, which needs to meet the requirements of complex engineering. Based on the large [...] Read more.
Marine load is an important factor affecting propeller propulsion efficiency, and the study of the wake evolution mechanism under different conditions is an essential part of the propeller equipment design, which needs to meet the requirements of complex engineering. Based on the large eddy simulation (LES) method, the wake instability characteristics are researched with the hydrodynamic load and wake dynamics theory, and the vortices composition and evolution mechanism under various load conditions are analyzed. Meanwhile, the propeller wake using the unsteady Reynolds-averaged Navier–Stokes (URANS) and LES methods is numerically simulated and compared. In addition, a comparison between a simulation and an experiment is carried out. The vortices evolution is described by dimensionless values of the velocity, pressure field, and vorticity field. The breaking and reassembling of different vortices are discussed. The results show that the pitch of the helicoidal tip vortices is larger under light loading conditions with high advance coefficients, and the wake is more stable, in contrast, which is smaller and the vortices break down earlier. By comparison, the topology of the vortices system is more complex under the low advance coefficient. Considering the interference effect between adjacent tip vortices, the energy dissipation is accelerated, resulting in the increased instability of vortices. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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12 pages, 274 KiB  
Article
Type I Shapovalov Wave Spacetimes in the Brans–Dicke Scalar-Tensor Theory of Gravity
by Konstantin Osetrin, Altair Filippov, Ilya Kirnos and Evgeny Osetrin
Symmetry 2022, 14(12), 2636; https://doi.org/10.3390/sym14122636 - 13 Dec 2022
Cited by 1 | Viewed by 714
Abstract
Exact solutions for Shapovalov wave spacetimes of type I in Brans–Dicke’s scalar-tensor theory of gravity are constructed. Shapovalov wave spacetimes describe gravitational wave models that allow for the the separation of wave variables in privileged coordinate systems. In contrast to general relativity, the [...] Read more.
Exact solutions for Shapovalov wave spacetimes of type I in Brans–Dicke’s scalar-tensor theory of gravity are constructed. Shapovalov wave spacetimes describe gravitational wave models that allow for the the separation of wave variables in privileged coordinate systems. In contrast to general relativity, the vacuum field equations of the Brans–Dicke scalar-tensor theory of gravity lead to exact solutions for type I Shapovalov spaces, allowing for the the construction of observational tests to detect such wave disturbances. Furthermore, the equations for the trajectories of the test particles are obtained for the models considered. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
9 pages, 243 KiB  
Article
Maxwell Equations in Homogeneous Spaces with Solvable Groups of Motions
by V. V. Obukhov
Symmetry 2022, 14(12), 2595; https://doi.org/10.3390/sym14122595 - 08 Dec 2022
Cited by 8 | Viewed by 833
Abstract
The classification of exact solutions of Maxwell vacuum equations for the case where the electromagnetic fields and metrics of homogeneous spaces are invariant with respect to the motion group G3(VII) was completed. All non-equivalent exact solutions of [...] Read more.
The classification of exact solutions of Maxwell vacuum equations for the case where the electromagnetic fields and metrics of homogeneous spaces are invariant with respect to the motion group G3(VII) was completed. All non-equivalent exact solutions of Maxwell vacuum equations for electromagnetic fields and spaces with such symmetry were obtained. The vectors of the canonical frame of a homogeneous space of type VII according to the Bianchi classification and the electromagnetic field potentials were found. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
18 pages, 1189 KiB  
Article
A Proposal for a Novel Formulation Based on the Hyperbolic Cattaneo’s Equation to Describe the Mechano-Transduction Process Occurring in Bone Remodeling
by Daria Scerrato, Ivan Giorgio, Alberto Maria Bersani and Daniele Andreucci
Symmetry 2022, 14(11), 2436; https://doi.org/10.3390/sym14112436 - 17 Nov 2022
Cited by 2 | Viewed by 908
Abstract
In this paper, we propose a model for the mechanical stimulus involved in the process of bone remodeling together with its evolution over time. Accumulated evidence suggests that bone remodeling could be interpreted as a feedback control process in which the mechanical state [...] Read more.
In this paper, we propose a model for the mechanical stimulus involved in the process of bone remodeling together with its evolution over time. Accumulated evidence suggests that bone remodeling could be interpreted as a feedback control process in which the mechanical state of the bone tissue is monitored, then appropriate signals are derived from the daily mechanical usage of the bone, these signals are transmitted into the surrounding region, and then they are detected by other agents whose purpose is to adapt the bone mass to the mechanical requirements of the environment. Therefore, we employ the diffusion equation for mass transport which is improved with Cattaneo’s correction to model the stimulus. This last improvement considers the effects of relaxation and non-locality, which we believe play essential roles in signaling messengers transport phenomena and are essential to match the evidence that suggests time-dependent excitations provide a more significant response at specific frequencies. To illustrate this particular behavior, numerical simulations have been performed in a 2D framework. The results fit the central aspect addressed, related to the dependency of the time of the adaptive process of bone, suggesting that our model is promising and deserves further investigation, both theoretical and experimental. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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15 pages, 1310 KiB  
Article
Attractive and Repulsive Fluctuation-Induced Pressure in Peptide Films Deposited on Semiconductor Substrates
by Galina L. Klimchitskaya, Vladimir M. Mostepanenko and Oleg Yu. Tsybin
Symmetry 2022, 14(10), 2196; https://doi.org/10.3390/sym14102196 - 19 Oct 2022
Cited by 2 | Viewed by 1073
Abstract
We consider the fluctuation-induced (Casimir) pressure in peptide films deposited on GaAs, Ge, and ZnS substrates which are either in a dielectric or metallic state. The calculations of the Casimir pressure are performed in the framework of the fundamental Lifshitz theory employing the [...] Read more.
We consider the fluctuation-induced (Casimir) pressure in peptide films deposited on GaAs, Ge, and ZnS substrates which are either in a dielectric or metallic state. The calculations of the Casimir pressure are performed in the framework of the fundamental Lifshitz theory employing the frequency-dependent dielectric permittivities of all involved materials. The electric conductivity of semiconductor substrates is taken into account within the experimentally and thermodynamically consistent approach. According to our results, the Casimir pressure in peptide films deposited on dielectric-type semiconductor substrates vanishes for some definite film thickness and is repulsive for thinner and attractive for thicker films. The dependence of this effect on the fraction of water in the film and on the static dielectric permittivity of the semiconductor substrate is determined. For the metallic-type semiconductor substrates, the Casimir pressure in peptide coatings is shown to be always repulsive. The possible applications of these results to the problem of stability of thin coatings in microdevices are discussed. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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27 pages, 2176 KiB  
Article
Symmetries of Quantum Fisher Information as Parameter Estimator for Pauli Channels under Indefinite Causal Order
by Francisco Delgado
Symmetry 2022, 14(9), 1813; https://doi.org/10.3390/sym14091813 - 01 Sep 2022
Cited by 3 | Viewed by 1516
Abstract
Quantum Fisher Information is considered in Quantum Information literature as the main resource to determine a bound in the parametric characterization problem of a quantum channel by means of probe states. The parameters characterizing a quantum channel can be estimated until a limited [...] Read more.
Quantum Fisher Information is considered in Quantum Information literature as the main resource to determine a bound in the parametric characterization problem of a quantum channel by means of probe states. The parameters characterizing a quantum channel can be estimated until a limited precision settled by the Cramér–Rao bound established in estimation theory and statistics. The involved Quantum Fisher Information of the emerging quantum state provides such a bound. Quantum states with dimension d=2, the qubits, still comprise the main resources considered in Quantum Information and Quantum Processing theories. For them, Pauli channels are an important family of parametric quantum channels providing the most faithful deformation effects of imperfect quantum communication channels. Recently, Pauli channels have been characterized when they are arranged in an Indefinite Causal Order. Thus, their fidelity has been compared with single or sequential arrangements of identical channels to analyse their induced transparency under a joint behaviour. The most recent characterization has exhibited important features for quantum communication related with their parametric nature. In this work, a parallel analysis has been conducted to extended such a characterization, this time in terms of their emerging Quantum Fisher Information to pursue the advantages of each kind of arrangement for the parameter estimation problem. The objective is to reach the arrangement stating the best estimation bound for each type of Pauli channel. A complete map for such an effectivity is provided for each Pauli channel under the most affordable setups considering sequential and Indefinite Causal Order arrangements, as well as discussing their advantages and disadvantages. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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Review

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76 pages, 2612 KiB  
Review
Tetraquarks and Pentaquarks from Quark Model Perspective
by Hongxia Huang, Chengrong Deng, Xuejie Liu, Yue Tan and Jialun Ping
Symmetry 2023, 15(7), 1298; https://doi.org/10.3390/sym15071298 - 22 Jun 2023
Cited by 12 | Viewed by 1250
Abstract
According to the classification of the quark model, the hadrons going beyond three-quark baryon and quark-antiquark meson pictures are called exotic hadrons. Many new hadrons have been observed since 2003, some of which exhibit exotic behaviors. There are a lot of excellent review [...] Read more.
According to the classification of the quark model, the hadrons going beyond three-quark baryon and quark-antiquark meson pictures are called exotic hadrons. Many new hadrons have been observed since 2003, some of which exhibit exotic behaviors. There are a lot of excellent review articles on exotic hadrons available so far; the present article tries to focus on the recent experimental and theoretical progress on the exotic states from the perspective of the quark model. Although lattice quantum chromodynamics may give the final answer of the problem, the phenomenological models are still powerful tools to explore the exotic states and to provide insight on the phenomenology of hadrons. The spatial and color structures of multiquark states and the channel coupling calculation are emphasized through reviewing some bound states, molecular and color structure resonances. Finally, the unquench effects of some exotic states are reviewed. With the accumulation of experimental data on multiquark states and inspiration of underlying theory developments, more reasonable phenomenological models incorporating multi-body interactions and high Fock components to unify the description of normal hadrons and exotic hadrons are expectable. Full article
(This article belongs to the Special Issue Physics and Symmetry Section: Feature Papers 2022)
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