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54 pages, 506 KiB  
Article
Enhancing Complex Decision-Making Under Uncertainty: Theory and Applications of q-Rung Neutrosophic Fuzzy Sets
by Omniyyah Saad Alqurashi and Kholood Mohammad Alsager
Symmetry 2025, 17(8), 1224; https://doi.org/10.3390/sym17081224 - 3 Aug 2025
Viewed by 188
Abstract
This thesis pioneers the development of q-Rung Neutrosophic Fuzzy Rough Sets (q-RNFRSs), establishing the first theoretical framework that integrates q-Rung Neutrosophic Sets with rough approximations to break through the conventional μq+ηq+νq1 constraint of existing [...] Read more.
This thesis pioneers the development of q-Rung Neutrosophic Fuzzy Rough Sets (q-RNFRSs), establishing the first theoretical framework that integrates q-Rung Neutrosophic Sets with rough approximations to break through the conventional μq+ηq+νq1 constraint of existing fuzzy–rough hybrids, achieving unprecedented capability in extreme uncertainty representation through our generalized model (Tq+Iq+Fq3). The work makes three fundamental contributions: (1) theoretical innovation through complete algebraic characterization of q-RNFRSs, including two distinct union/intersection operations and four novel classes of complement operators (with Theorem 1 verifying their involution properties via De Morgan’s Laws); (2) clinical breakthrough via a domain-independent medical decision algorithm featuring dynamic q-adaptation (q = 2–4) for criterion-specific uncertainty handling, demonstrating 90% diagnostic accuracy in validation trials—a 22% improvement over static models (p<0.001); and (3) practical impact through multi-dimensional uncertainty modeling (truth–indeterminacy–falsity), robust therapy prioritization under data incompleteness, and computationally efficient approximations for real-world clinical deployment. Full article
(This article belongs to the Special Issue The Fusion of Fuzzy Sets and Optimization Using Symmetry)
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19 pages, 1806 KiB  
Article
A Novel Approach to Solving Generalised Nonlinear Dynamical Systems Within the Caputo Operator
by Mashael M. AlBaidani and Rabab Alzahrani
Fractal Fract. 2025, 9(8), 503; https://doi.org/10.3390/fractalfract9080503 - 31 Jul 2025
Viewed by 137
Abstract
In this study, we focus on solving the nonlinear time-fractional Hirota–Satsuma coupled Korteweg–de Vries (KdV) and modified Korteweg–de Vries (MKdV) equations, using the Yang transform iterative method (YTIM). This method combines the Yang transform with a new iterative scheme to construct reliable and [...] Read more.
In this study, we focus on solving the nonlinear time-fractional Hirota–Satsuma coupled Korteweg–de Vries (KdV) and modified Korteweg–de Vries (MKdV) equations, using the Yang transform iterative method (YTIM). This method combines the Yang transform with a new iterative scheme to construct reliable and efficient solutions. Readers can understand the procedures clearly, since the implementation of Yang transform directly transforms fractional derivative sections into algebraic terms in the given problems. The new iterative scheme is applied to generate series solutions for the provided problems. The fractional derivatives are considered in the Caputo sense. To validate the proposed approach, two numerical examples are analysed and compared with exact solutions, as well as with the results obtained from the fractional reduced differential transform method (FRDTM) and the q-homotopy analysis transform method (q-HATM). The comparisons, presented through both tables and graphical illustrations, confirm the enhanced accuracy and reliability of the proposed method. Moreover, the effect of varying the fractional order is explored, demonstrating convergence of the solution as the order approaches an integer value. Importantly, the time-fractional Hirota–Satsuma coupled KdV and modified Korteweg–de Vries (MKdV) equations investigated in this work are not only of theoretical and computational interest but also possess significant implications for achieving global sustainability goals. Specifically, these equations contribute to the Sustainable Development Goal (SDG) “Life Below Water” by offering advanced modelling capabilities for understanding wave propagation and ocean dynamics, thus supporting marine ecosystem research and management. It is also relevant to SDG “Climate Action” as it aids in the simulation of environmental phenomena crucial to climate change analysis and mitigation. Additionally, the development and application of innovative mathematical modelling techniques align with “Industry, Innovation, and Infrastructure” promoting advanced computational tools for use in ocean engineering, environmental monitoring, and other infrastructure-related domains. Therefore, the proposed method not only advances mathematical and numerical analysis but also fosters interdisciplinary contributions toward sustainable development. Full article
(This article belongs to the Special Issue Recent Trends in Computational Physics with Fractional Applications)
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14 pages, 275 KiB  
Article
New Identities and Equation Solutions Involving k-Oresme and k-Oresme–Lucas Sequences
by Bahar Demirtürk
Mathematics 2025, 13(14), 2321; https://doi.org/10.3390/math13142321 - 21 Jul 2025
Viewed by 244
Abstract
Number sequences are among the research areas of interest in both number theory and linear algebra. In particular, the study of matrix representations of recursive sequences is important in revealing the structural properties of these sequences. In this study, the relationships between the [...] Read more.
Number sequences are among the research areas of interest in both number theory and linear algebra. In particular, the study of matrix representations of recursive sequences is important in revealing the structural properties of these sequences. In this study, the relationships between the elements of the k-Fibonacci and k-Oresme sequences were analyzed using matrix algebra through matrix structures created by connecting the characteristic equations and roots of these sequences. In this context, using the properties of these matrices, the identities An2An+1An1=k2n, An2AnAn1+1k2An12=k2n, and Bn2BnBn1+1k2Bn12=(k24)k2n, and some generalizations such as Bn+m2(k24)AntBn+mAt+m(k24)k2t2nAt+m2=k2m2tBnt2, At+m2BtnAn+mAt+m+k2n2tAn+m2=k2n2mAtn2, and more were derived, where m,n,t and tn. In addition to this, the solution pairs of the algebraic equations x2Bpxy+k2py2=k2qAp2, x2(k24)Apxy(k24)k2py2=k2qBp2, and x2Bpxy+k2py2=(k24)k2qAp2 are presented, where Ap and Bp are k-Oresme and k-Oresme–Lucas numbers, respectively. Full article
(This article belongs to the Section A: Algebra and Logic)
21 pages, 315 KiB  
Article
Module Algebra Structures of Non-Standard Quantum Group Xq(A1) on C[x,y,z]
by Dong Su
Mathematics 2025, 13(14), 2227; https://doi.org/10.3390/math13142227 - 8 Jul 2025
Viewed by 257
Abstract
In this paper, we investigate the module algebra structures of Xq(A1) on the quantum polynomial algebra Cq[x,y,z]. The automorphism group of [...] Read more.
In this paper, we investigate the module algebra structures of Xq(A1) on the quantum polynomial algebra Cq[x,y,z]. The automorphism group of Cq[x,y,z] is denoted by Aut(Cq[x,y,z]), and we give a complete classification of Xq(A1)-module algebra structures on Cq[x,y,z], where K1,K2Aut(Cq[x,y,z]). Full article
24 pages, 1601 KiB  
Article
Finding the q-Appell Convolution of Certain Polynomials Within the Context of Quantum Calculus
by Waseem Ahmad Khan, Khidir Shaib Mohamed, Francesco Aldo Costabile, Can Kızılateş and Cheon Seoung Ryoo
Mathematics 2025, 13(13), 2073; https://doi.org/10.3390/math13132073 - 23 Jun 2025
Cited by 1 | Viewed by 206
Abstract
This article introduces the theory of three-variable q-truncated exponential Gould–Hopper-based Appell polynomials by employing a generating function approach that incorporates q-calculus functions. This study further explores these polynomials by using a computational algebraic approach. The determinant form, recurrences, and differential equations [...] Read more.
This article introduces the theory of three-variable q-truncated exponential Gould–Hopper-based Appell polynomials by employing a generating function approach that incorporates q-calculus functions. This study further explores these polynomials by using a computational algebraic approach. The determinant form, recurrences, and differential equations are proven. Relationships with the monomiality principle are given. Finally, graphical representations are presented to illustrate the behavior and potential applications of the three-variable q-truncated exponential Gould–Hopper-based Appell polynomials. Full article
(This article belongs to the Special Issue Polynomials: Theory and Applications, 2nd Edition)
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23 pages, 317 KiB  
Article
On the Symbols of Strictly m-Null Elementary Operators
by Isabel Marrero
Mathematics 2025, 13(12), 2026; https://doi.org/10.3390/math13122026 - 19 Jun 2025
Cited by 1 | Viewed by 657
Abstract
This paper extends the previous work by the author on m-null pairs of operators in Hilbert space. If an elementary operator L has elementary symbols A and B that are p-null and q-null, respectively, then L is  [...] Read more.
This paper extends the previous work by the author on m-null pairs of operators in Hilbert space. If an elementary operator L has elementary symbols A and B that are p-null and q-null, respectively, then L is (p+q1)-null. Here, we prove the converse under strictness conditions, modulo some nonzero multiplicative constant—if L is strictly (p+q1)-null, then a scalar λ0 exists such that λA is strictly p-null and λ1B is strictly q-null. Our constructive argument relies essentially on algebraic and combinatorial methods. Thus, the result obtained by Gu on m-isometries is recovered without resorting to spectral analysis. For several operator classes that generalize m-isometries and are subsumed by m-null operators, the result is new. Full article
(This article belongs to the Section C: Mathematical Analysis)
24 pages, 313 KiB  
Article
Common Neighborhood Energy of the Non-Commuting Graphs and Commuting Graphs Associated with Dihedral and Generalized Quaternion Groups
by Hanaa Alashwali and Anwar Saleh
Mathematics 2025, 13(11), 1834; https://doi.org/10.3390/math13111834 - 30 May 2025
Viewed by 295
Abstract
This paper explores the common neighborhood energy (ECN(Γ)) of graphs derived from the dihedral group D2n and generalized quaternion group Q4n, specifically the non-commuting graph (NCM-graph) and the commuting graph (CM-graph). [...] Read more.
This paper explores the common neighborhood energy (ECN(Γ)) of graphs derived from the dihedral group D2n and generalized quaternion group Q4n, specifically the non-commuting graph (NCM-graph) and the commuting graph (CM-graph). Studying graphs associated with groups offers a powerful approach to translating algebraic properties into combinatorial structures, enabling the application of graph-theoretic tools to understand group behavior. The common neighborhood energy, defined as the sum of the absolute values of the eigenvalues of the common neighborhood (CN) matrix, i.e., i=1p|ζi|, where {ζi}i=1p are the CN eigenvalues, provides insights into the structural properties of these graphs. We derive explicit formulas for the CN characteristic polynomials and corresponding CN eigenvalues for both the NCM-graph and CM-graph as functions of n. Consequently, we establish closed-form expressions for the ECN of these graphs, which are parameterized by n. The validity of our theoretical results is confirmed through computational examples. This study contributes to the spectral analysis of algebraic graphs, demonstrating a direct connection between the group-theoretic structure of D2n and Q4n, as well as the combinatorial energy of their associated graphs, thus furthering the understanding of group properties through spectral graph theory. Full article
(This article belongs to the Special Issue Algebraic Combinatorics and Spectral Graph Theory)
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32 pages, 1301 KiB  
Article
A Novel Multi-Q Valued Bipolar Picture Fuzzy Set Approach for Evaluating Cybersecurity Risks
by Nidaa Mohammed Alsughayyir and Kholood Mohammad Alsager
Symmetry 2025, 17(5), 749; https://doi.org/10.3390/sym17050749 - 13 May 2025
Viewed by 335
Abstract
This paper presents a unique multi-Q valued bipolar picture fuzzy set (MQVBPFS) methodology to tackle issues in cybersecurity risk assessment under conditions of ambiguity and contradicting data. The MQVBPFS framework enhances classical fuzzy theory through three key innovations: (1) multi-granular Q-valued membership, (2) [...] Read more.
This paper presents a unique multi-Q valued bipolar picture fuzzy set (MQVBPFS) methodology to tackle issues in cybersecurity risk assessment under conditions of ambiguity and contradicting data. The MQVBPFS framework enhances classical fuzzy theory through three key innovations: (1) multi-granular Q-valued membership, (2) integrated bipolarity for representing conflicting evidence, and (3) refined algebraic operations, encompassing union, intersection, and complement. Contemporary fuzzy set methodologies, such as intuitionistic and image fuzzy sets, inadequately encapsulate positive, negative, and neutral membership degrees while maintaining bipolar information. Conversely, our MQVBPFS architecture effectively resolves this restriction. Utilizing this framework for threat assessment and risk ranking, we create a tailored cybersecurity algorithm that exhibits 91.7% accuracy (in contrast to 78.2–83.5% for baseline methods) and attains 94.6% contradiction tolerance in empirical evaluations, alongside an 18% decrease in false negatives relative to conventional approaches. This study offers theoretical progress in fuzzy set algebra and practical enhancements in security analytics, improving the handling of ambiguous and conflicting threat data while facilitating new research avenues in uncertainty-aware cybersecurity systems. Full article
(This article belongs to the Section Mathematics)
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20 pages, 321 KiB  
Article
Constructing Q-Ideals for Boolean Semiring Partitioning Using Seeds
by Claudia Ledbury Justus, Karin-Therese Howell and Cang Hui
Mathematics 2025, 13(8), 1250; https://doi.org/10.3390/math13081250 - 10 Apr 2025
Viewed by 338
Abstract
Semiring partitioning is widely used in mathematics, computer science, and data analysis. The purpose of this paper is to add to the theory of semirings by proposing a novel method to construct Q-ideals for partitioning Boolean semirings. We introduce the set of [...] Read more.
Semiring partitioning is widely used in mathematics, computer science, and data analysis. The purpose of this paper is to add to the theory of semirings by proposing a novel method to construct Q-ideals for partitioning Boolean semirings. We introduce the set of all seeds—all s-tuples over a particular Boolean algebra—and the notion of their weight and complement. Utilizing this new method for constructing Q-ideals, we develop a nested hierarchical partitioning algorithm based on the weight of selected seeds. Additionally, we determine the maximal semiring homomorphism corresponding to this proposed method. Full article
(This article belongs to the Section A: Algebra and Logic)
11 pages, 241 KiB  
Article
On the Strong Atoms of Q-Algebras
by Kittisak Saengsura, Napaporn Sarasit and Ananya Anantayasethi
Axioms 2025, 14(4), 271; https://doi.org/10.3390/axioms14040271 - 3 Apr 2025
Viewed by 319
Abstract
The concept of strong atoms in Q-algebras is discussed herein. In this work, some properties of strong atoms are provided. We show that there is no Q-algebra X with |X|3 such that all elements are strong atoms. [...] Read more.
The concept of strong atoms in Q-algebras is discussed herein. In this work, some properties of strong atoms are provided. We show that there is no Q-algebra X with |X|3 such that all elements are strong atoms. We also find that any two-element subset of X containing a constant 0 is a subalgebra of X whenever X contains a strong atom. Moreover, any subset of X with the cardinality equal to 3 containing a strong atom and a constant 0 is always a subalgebra. We present some results concerning the concept of an ideal. In a Q-algebra X that contains a strong atom, any ideal of X is a subalgebra of X. An ideal of a Q-algebra X that is induced by any subset containing a strong atom is equal to X. Furthermore, we show that, for any Q-algebra X with a strong atom, there is only one ideal containing a strong atom. In particular, for |X|4, we propose that a finite union of ideals of X is again an ideal of X. Full article
(This article belongs to the Section Algebra and Number Theory)
21 pages, 448 KiB  
Article
A Contemporary Algebraic Attributes of m-Polar Q-Hesitant Fuzzy Sets in BCK/BCI Algebras and Applications of Career Determination
by Kholood Mohammad Alsager
Symmetry 2025, 17(4), 535; https://doi.org/10.3390/sym17040535 - 31 Mar 2025
Cited by 1 | Viewed by 306
Abstract
To systematically address the intricate multiple criteria decision-making (MCDM) challenges to practical situations where uncertain and hesitant information plays a critical role in guiding optimal choices. In this article, we introduce the concept of m-polar Q-hesitant fuzzy (MPQHF) [...] Read more.
To systematically address the intricate multiple criteria decision-making (MCDM) challenges to practical situations where uncertain and hesitant information plays a critical role in guiding optimal choices. In this article, we introduce the concept of m-polar Q-hesitant fuzzy (MPQHF) BCK/BCI algebras, combining m-PFS theory with Q-hesitant fuzzy set theory in the framework of BCK/BCI algebras. This innovative approach enhances the attitudes of uncertainty, vagueness, and hesitance of data in decision-making processes. We investigate the features and actions of this proposed hybrid approach to fuzzy sets and hesitant fuzzy sets, focusing on MPQHF subalgebras, and explore the characteristics of several kinds of ideals under BCK/BCI algebras. It also showed that it can better represent complex levels of uncertainty than regular sets. The proposed method’s theoretical framework offers a better way to show uncertain data in areas like engineering, computer science, and computational mathematics. By linking theoretical advancements of MPQHF sets with practical applications, we highlight the benefits and challenges of this approach. Demonstrating the practical uses of the MPQHF sets aims to encourage broader adoption. Symmetry plays a vital role in algebraic structure and is used in various fields like decision-making, encryption, pattern recognition problems, and automata theory. Furthermore, this work enhances the understanding of algebraic structures and offers a robust tool for career exploration and development through improved decision-making methodologies. Full article
(This article belongs to the Section Mathematics)
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18 pages, 376 KiB  
Article
Traveling-Wave Solutions of Several Nonlinear Mathematical Physics Equations
by Petar Popivanov and Angela Slavova
Mathematics 2025, 13(6), 901; https://doi.org/10.3390/math13060901 - 7 Mar 2025
Viewed by 824
Abstract
This paper deals with several nonlinear partial differential equations (PDEs) of mathematical physics such as the concatenation model (perturbed concatenation model) from nonlinear fiber optics, the plane hydrodynamic jet theory, the Kadomtsev–Petviashvili PDE from hydrodynamic (soliton theory) and others. For the equation of [...] Read more.
This paper deals with several nonlinear partial differential equations (PDEs) of mathematical physics such as the concatenation model (perturbed concatenation model) from nonlinear fiber optics, the plane hydrodynamic jet theory, the Kadomtsev–Petviashvili PDE from hydrodynamic (soliton theory) and others. For the equation of nonlinear optics, we look for solutions of the form amplitude Q multiplied by eiΦ, Φ being linear. Then, Q is expressed as a quadratic polynomial of some elliptic function. Such types of solutions exist if some nonlinear algebraic system possesses a nontrivial solution. In the other five cases, the solution is a traveling wave. It satisfies Abel-type ODE of the second kind, the first order ODE of the elliptic functions (the Weierstrass or Jacobi functions), the Airy equation, the Emden–Fawler equation, etc. At the end of the paper a short survey on the Jacobi elliptic and Weierstrass functions is included. Full article
(This article belongs to the Section C1: Difference and Differential Equations)
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19 pages, 292 KiB  
Article
A Novel Method to Calculate Nonlocal Symmetries from Local Symmetries
by Andronikos Paliathanasis
Symmetry 2025, 17(3), 340; https://doi.org/10.3390/sym17030340 - 24 Feb 2025
Cited by 1 | Viewed by 361
Abstract
We explore nonlocal symmetries in a class of Hamiltonian dynamical systems governed by second-order differential equations. Specifically, we establish an algorithm for deriving nonlocal symmetries by utilizing the Jacobi metric and the Eisenhart–Duval lift to geometrize the dynamical systems. The geometrized systems often [...] Read more.
We explore nonlocal symmetries in a class of Hamiltonian dynamical systems governed by second-order differential equations. Specifically, we establish an algorithm for deriving nonlocal symmetries by utilizing the Jacobi metric and the Eisenhart–Duval lift to geometrize the dynamical systems. The geometrized systems often exhibit additional local symmetries compared to the original systems, some of which correspond to nonlocal symmetries for the original formulation. This novel approach allows us to determine nonlocal symmetries in a systematic way. Within this geometric framework, we demonstrate that the second-order differential equation q¨Fq=0 admits an infinite number of nonlocal symmetries generated by the infinite-dimensional conformal algebra of a two-dimensional Riemannian manifold. Applications to higher-dimensional systems are also discussed. Full article
(This article belongs to the Special Issue Symmetry in Hamiltonian Dynamical Systems)
48 pages, 1898 KiB  
Essay
The Code Underneath
by Julio Rives
Axioms 2025, 14(2), 106; https://doi.org/10.3390/axioms14020106 - 30 Jan 2025
Viewed by 811
Abstract
An inverse-square probability mass function (PMF) is at the Newcomb–Benford law (NBL)’s root and ultimately at the origin of positional notation and conformality. PrZ=2Z2, where ZZ+. Under its tail, we find information [...] Read more.
An inverse-square probability mass function (PMF) is at the Newcomb–Benford law (NBL)’s root and ultimately at the origin of positional notation and conformality. PrZ=2Z2, where ZZ+. Under its tail, we find information as harmonic likelihood Ls,t=Ht1Hs1, where Hn is the nth harmonic number. The global Q-NBL is Prb,q=Lq,q+1L1,b=qHb11, where b is the base and q is a quantum (1q<b). Under its tail, we find information as logarithmic likelihood i,j=lnji. The fiducial R-NBL is Prr,d=d,d+11,r=logr1+1d, where rb is the radix of a local complex system. The global Bayesian rule multiplies the correlation between two numbers, s and t, by a likelihood ratio that is the NBL probability of bucket s,t relative to b’s support. To encode the odds of quantum j against i locally, we multiply the prior odds Prb,jPrb,i by a likelihood ratio, which is the NBL probability of bin i,j relative to r’s support; the local Bayesian coding rule is o˜j:i|r=ijlogrji. The Bayesian rule to recode local data is o˜j:i|r=o˜j:i|rlnrlnr. Global and local Bayesian data are elements of the algebraic field of “gap ratios”, ABCD. The cross-ratio, the central tool in conformal geometry, is a subclass of gap ratio. A one-dimensional coding source reflects the global Bayesian data of the harmonic external world, the annulus xQ|1x<b, into the local Bayesian data of its logarithmic coding space, the ball xQ|x<11b. The source’s conformal encoding function is y=logr2x1, where x is the observed Euclidean distance to an object’s position. The conformal decoding function is x=121+ry. Both functions, unique under basic requirements, enable information- and granularity-invariant recursion to model the multiscale reality. Full article
(This article belongs to the Special Issue Mathematical Modelling of Complex Systems)
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20 pages, 304 KiB  
Article
Derivation of Tensor Algebra as a Fundamental Operation—The Fermi Derivative in a General Metric Affine Space
by Michael Tsamparlis
Symmetry 2025, 17(1), 81; https://doi.org/10.3390/sym17010081 - 7 Jan 2025
Viewed by 898
Abstract
The aim of this work is to demonstrate that all linear derivatives of the tensor algebra over a smooth manifold M can be viewed as specific cases of a broader concept—the operation of derivation. This approach reveals the universal role of differentiation, which [...] Read more.
The aim of this work is to demonstrate that all linear derivatives of the tensor algebra over a smooth manifold M can be viewed as specific cases of a broader concept—the operation of derivation. This approach reveals the universal role of differentiation, which simplifies and generalizes the study of tensor derivatives, making it a powerful tool in Differential Geometry and related fields. To perform this, the generic derivative is introduced, which is defined in terms of the quantities Qk(i)(X). Subsequently, the transformation law of these quantities is determined by the requirement that the generic derivative of a tensor is a tensor. The quantities Qk(i)(X) and their transformation law define a specific geometric object on M, and consequently, a geometric structure on M. Using the generic derivative, one defines the tensor fields of torsion and curvature and computes them for all linear derivatives in terms of the quantities Qk(i)(X). The general model is applied to the cases of Lie derivative, covariant derivative, and Fermi derivative. It is shown that the Lie derivative has non-zero torsion and zero curvature due to the Jacobi identity. For the covariant derivative, the standard results follow without any further calculations. Concerning the Fermi derivative, this is defined in a new way, i.e., as a higher-order derivative defined in terms of two derivatives: a given derivative and the Lie derivative. Being linear derivative, it has torsion and curvature tensor. These fields are computed in a general affine space from the corresponding general expressions of the generic derivative. Applications of the above considerations are discussed in a number of cases. Concerning the Lie derivative, it is been shown that the Poisson bracket is in fact a Lie derivative. Concerning the Fermi derivative, two applications are considered: (a) the explicit computation of the Fermi derivative in a general affine space and (b) the consideration of Freedman–Robertson–Walker spacetime endowed with a scalar torsion field, which satisfies the Cosmological Principle and the computation of Fermi derivative of the spatial directions defining a spatial frame along the cosmological fluid of comoving observers. It is found that torsion, even in this highly symmetric case, induces a kinematic rotation of the space axes, questioning the interpretation of torsion as a spin. Finally it is shown that the Lie derivative of the dynamical equations of an autonomous conservative dynamical system is equivalent to the standard Lie symmetry method. Full article
(This article belongs to the Special Issue Advances in Nonlinear Systems and Symmetry/Asymmetry)
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