Pub Date : 2025-01-29DOI: 10.1007/s00006-025-01370-1
Zhiqiang Wang, Xingya Fan
This paper presents a discussion on the branching problem that arises in the Weil representation of the exceptional Lie group of type (G_2). The focus is on its decomposition under the threefold cover of (SL(2,, {mathbb {R}})) associated with the short root of (G_2).
{"title":"Branching of Weil Representation for $$G_2$$","authors":"Zhiqiang Wang, Xingya Fan","doi":"10.1007/s00006-025-01370-1","DOIUrl":"https://doi.org/10.1007/s00006-025-01370-1","url":null,"abstract":"<p>This paper presents a discussion on the branching problem that arises in the Weil representation of the exceptional Lie group of type <span>(G_2)</span>. The focus is on its decomposition under the threefold cover of <span>(SL(2,, {mathbb {R}}))</span> associated with the short root of <span>(G_2)</span>.</p>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"74 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143056622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-22DOI: 10.1007/s00006-025-01372-z
Andrey Krutov, Pavle Pandžić
We construct the q-deformed Clifford algebra of (mathfrak {sl}_2) and study its properties. This allows us to define the q-deformed noncommutative Weil algebra (mathcal {W}_q(mathfrak {sl}_2)) for (U_q(mathfrak {sl}_2)) and the corresponding cubic Dirac operator (D_q). In the classical case this was done by Alekseev and Meinrenken in 2000. We show that the cubic Dirac operator (D_q) is invariant with respect to the (U_q({mathfrak {sl}}_2))-action and (*)-structures on (mathcal {W}_q(mathfrak {sl}_2)), moreover, the square of (D_q) is central in (mathcal {W}_q(mathfrak {sl}_2)). We compute the spectrum of the cubic element on finite-dimensional and Verma modules of (U_q(mathfrak {sl}_2)) and the corresponding Dirac cohomology.
{"title":"Cubic Dirac operator for (U_q({mathfrak {sl}}_2))","authors":"Andrey Krutov, Pavle Pandžić","doi":"10.1007/s00006-025-01372-z","DOIUrl":"10.1007/s00006-025-01372-z","url":null,"abstract":"<div><p>We construct the <i>q</i>-deformed Clifford algebra of <span>(mathfrak {sl}_2)</span> and study its properties. This allows us to define the <i>q</i>-deformed noncommutative Weil algebra <span>(mathcal {W}_q(mathfrak {sl}_2))</span> for <span>(U_q(mathfrak {sl}_2))</span> and the corresponding cubic Dirac operator <span>(D_q)</span>. In the classical case this was done by Alekseev and Meinrenken in 2000. We show that the cubic Dirac operator <span>(D_q)</span> is invariant with respect to the <span>(U_q({mathfrak {sl}}_2))</span>-action and <span>(*)</span>-structures on <span>(mathcal {W}_q(mathfrak {sl}_2))</span>, moreover, the square of <span>(D_q)</span> is central in <span>(mathcal {W}_q(mathfrak {sl}_2))</span>. We compute the spectrum of the cubic element on finite-dimensional and Verma modules of <span>(U_q(mathfrak {sl}_2))</span> and the corresponding Dirac cohomology.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-21DOI: 10.1007/s00006-025-01369-8
Moab Croft, Hamish Todd, Edward Corbett
This paper presents the Geometric Algebra approach to the Wigner little group for photons using the Spacetime Algebra, incorporating a mirror-based view for physical interpretation. The shift from a point-based view to a mirror-based view is a modern movement that allows for a more intuitive representation of geometric and physical entities, with vectors and their higher-grade counterparts viewed as hyperplanes. This reinterpretation simplifies the implementation of homogeneous representations of geometric objects within the Spacetime Algebra and enables a relative view via projective geometry. Then, after utilizing the intrinsic properties of Geometric Algebra, the Wigner little group is seen to induce a projective geometric algebra as a subalgebra of the Spacetime Algebra. However, the dimension-agnostic nature of Geometric Algebra enables the generalization of induced subalgebras to ((1+n))-dimensional Minkowski geometric algebras, termed little photon algebras. The lightlike transformations (translations) in these little photon algebras are seen to leave invariant the (pseudo)canonical electromagetic field bivector. Geometrically, this corresponds to Lorentz transformations that do not change the intersection of the spacelike polarization hyperplane with the lightlike wavevector hyperplane while simultaneously not affecting the lightlike wavevector hyperplane. This provides for a framework that unifies the analysis of symmetries and substructures of point-based Geometric Algebra with mirror-based Geometric Algebra.
{"title":"The Wigner Little Group for Photons is a Projective Subalgebra","authors":"Moab Croft, Hamish Todd, Edward Corbett","doi":"10.1007/s00006-025-01369-8","DOIUrl":"10.1007/s00006-025-01369-8","url":null,"abstract":"<div><p>This paper presents the Geometric Algebra approach to the Wigner little group for photons using the Spacetime Algebra, incorporating a mirror-based view for physical interpretation. The shift from a <i>point-based view</i> to a <i>mirror-based view</i> is a modern movement that allows for a more intuitive representation of geometric and physical entities, with vectors and their higher-grade counterparts viewed as hyperplanes. This reinterpretation simplifies the implementation of homogeneous representations of geometric objects within the Spacetime Algebra and enables a <i>relative view</i> via projective geometry. Then, after utilizing the intrinsic properties of Geometric Algebra, the Wigner little group is seen to induce a projective geometric algebra as a subalgebra of the Spacetime Algebra. However, the dimension-agnostic nature of Geometric Algebra enables the generalization of induced subalgebras to <span>((1+n))</span>-dimensional Minkowski geometric algebras, termed <i>little photon algebras</i>. The lightlike transformations (translations) in these little photon algebras are seen to leave invariant the (pseudo)<i>canonical electromagetic field bivector</i>. Geometrically, this corresponds to Lorentz transformations that do not change the intersection of the spacelike polarization hyperplane with the lightlike wavevector hyperplane while simultaneously not affecting the lightlike wavevector hyperplane. This provides for a framework that unifies the analysis of symmetries and substructures of point-based Geometric Algebra with mirror-based Geometric Algebra.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-18DOI: 10.1007/s00006-025-01371-0
Yufeng Wang, Zhongxiang Zhang
In this article, we verify the boundedness of the Cauchy type integral operators under the generalized Hölder norm in Clifford analysis, which are called H-B theorems of the Cauchy integral operators in Clifford analysis. We first demonstrate the generalized 2P theorems and the generalized Muskhelishvili theorem in Clifford analysis by Du’s method derived from Du (J Math (PRC) 2(2):115–12, 1982) and Lu (Boundary value problems of analytic functions. World Scientific, Singapore, 1993), which greatly refines the coefficients estimate of inequality in Du et al. (Acta Math Sci 29B(1):210–224, 2009) and Zhang (Complex Var Elliptic Equ 52(6):455–473, 2007). Then, we obtain the H-B theorems which extend and improve the corresponding results in Du et al. (2009) and Wang and Du (Z Anal Anwend, 2024).
本文证明了Clifford分析中广义Hölder范数下柯西型积分算子的有界性,称为Clifford分析中柯西积分算子的H-B定理。本文首先利用Du (J Math (PRC) 2(2):115 - 12,1982)和Lu(解析函数的边值问题)导出的Du方法,证明了Clifford分析中的广义2P定理和广义Muskhelishvili定理。世界科学,新加坡,1993),大大改进了Du等人(数学学报29B(1): 210-224, 2009)和Zhang(复Var椭圆方程52(6):455-473,2007)的不等式系数估计。然后,我们得到了H-B定理,该定理扩展和改进了Du et al.(2009)和Wang and Du (Z Anal Anwend, 2024)的相应结果。
{"title":"H-B Theorems of Cauchy Integral Operators in Clifford Analysis","authors":"Yufeng Wang, Zhongxiang Zhang","doi":"10.1007/s00006-025-01371-0","DOIUrl":"10.1007/s00006-025-01371-0","url":null,"abstract":"<div><p>In this article, we verify the boundedness of the Cauchy type integral operators under the generalized Hölder norm in Clifford analysis, which are called H-B theorems of the Cauchy integral operators in Clifford analysis. We first demonstrate the generalized 2P theorems and the generalized Muskhelishvili theorem in Clifford analysis by Du’s method derived from Du (J Math (PRC) 2(2):115–12, 1982) and Lu (Boundary value problems of analytic functions. World Scientific, Singapore, 1993), which greatly refines the coefficients estimate of inequality in Du et al. (Acta Math Sci 29B(1):210–224, 2009) and Zhang (Complex Var Elliptic Equ 52(6):455–473, 2007). Then, we obtain the H-B theorems which extend and improve the corresponding results in Du et al. (2009) and Wang and Du (Z Anal Anwend, 2024).</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-17DOI: 10.1007/s00006-025-01373-y
Derek Courchesne, Sébastien Tremblay
In this article we study some algebraic aspects of multicomplex numbers ({mathbb {M}}_n). For (nge 2) a canonical representation is defined in terms of the multiplication of (n-1) idempotent elements. This representation facilitates computations in this algebra and makes it possible to introduce a generalized conjugacy (Lambda _n), i.e. a composition of the n multicomplex conjugates (Lambda _n:=dagger _1cdots dagger _n), as well as a multicomplex norm. The ideals of the ring of multicomplex numbers are then studied in details, free ({mathbb {M}}_n)-modules and their linear operators are considered and, finally, we develop Hilbert spaces on the multicomplex algebra.
{"title":"Multicomplex Ideals, Modules and Hilbert Spaces","authors":"Derek Courchesne, Sébastien Tremblay","doi":"10.1007/s00006-025-01373-y","DOIUrl":"10.1007/s00006-025-01373-y","url":null,"abstract":"<div><p>In this article we study some algebraic aspects of multicomplex numbers <span>({mathbb {M}}_n)</span>. For <span>(nge 2)</span> a canonical representation is defined in terms of the multiplication of <span>(n-1)</span> idempotent elements. This representation facilitates computations in this algebra and makes it possible to introduce a generalized conjugacy <span>(Lambda _n)</span>, i.e. a composition of the <i>n</i> multicomplex conjugates <span>(Lambda _n:=dagger _1cdots dagger _n)</span>, as well as a multicomplex norm. The ideals of the ring of multicomplex numbers are then studied in details, free <span>({mathbb {M}}_n)</span>-modules and their linear operators are considered and, finally, we develop Hilbert spaces on the multicomplex algebra.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142987799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-19DOI: 10.1007/s00006-024-01362-7
Bernd Schmeikal
In the present article, the research work of many years is summarized in an interim report. This concerns the connection between logic, space, time and matter. The author always had in mind two things, namely 1. The discovery/construction of an interface between matter and mind, and 2. some entry points for the topos view that concern graphs, grade rotations and contravariant involutions in geometric Boolean lattices. In this part of the MiTopos theme I follow the historic approach to mathematical physics and remain with the Clifford algebra of the Minkowski space. It turns out that this interface is a basic morphogenetic structure inherent in both matter and thought. It resides in both oriented spaces and logic, and most surprisingly is closely linked to the symmetries of elementary particle physics.
{"title":"MiTopos","authors":"Bernd Schmeikal","doi":"10.1007/s00006-024-01362-7","DOIUrl":"10.1007/s00006-024-01362-7","url":null,"abstract":"<div><p>In the present article, the research work of many years is summarized in an interim report. This concerns the connection between logic, space, time and matter. The author always had in mind two things, namely 1. The discovery/construction of an interface between matter and mind, and 2. some entry points for the topos view that concern graphs, grade rotations and contravariant involutions in geometric Boolean lattices. In this part of the MiTopos theme I follow the historic approach to mathematical physics and remain with the Clifford algebra of the Minkowski space. It turns out that this interface is a basic morphogenetic structure inherent in both matter and thought. It resides in both oriented spaces and logic, and most surprisingly is closely linked to the symmetries of elementary particle physics.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-11DOI: 10.1007/s00006-024-01368-1
C. J. Robson
The study of complex functions is based around the study of holomorphic functions, satisfying the Cauchy-Riemann equations. The relatively recent field of Clifford Analysis lets us extend many results from Complex Analysis to higher dimensions. In this paper, I decompose the Cauchy-Riemann equations for a general Clifford algebra into grades using the Geometric Algebra formalism, and show that for the Spacetime Algebra Cl(3, 1) these equations are the equations for a self-dual source free Maxwell field, and for a massless uncharged Spinor. This shows a deep link between fundamental physics and the Clifford geometry of Spacetime.
{"title":"Self-Dual Maxwell Fields from Clifford Analysis","authors":"C. J. Robson","doi":"10.1007/s00006-024-01368-1","DOIUrl":"10.1007/s00006-024-01368-1","url":null,"abstract":"<div><p>The study of complex functions is based around the study of holomorphic functions, satisfying the Cauchy-Riemann equations. The relatively recent field of Clifford Analysis lets us extend many results from Complex Analysis to higher dimensions. In this paper, I decompose the Cauchy-Riemann equations for a general Clifford algebra into grades using the Geometric Algebra formalism, and show that for the Spacetime Algebra <i>Cl</i>(3, 1) these equations are the equations for a self-dual source free Maxwell field, and for a massless uncharged Spinor. This shows a deep link between fundamental physics and the Clifford geometry of Spacetime.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00006-024-01368-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142809682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-02DOI: 10.1007/s00006-024-01367-2
Weihua Chen, Caiqin Song
In this paper, we apply the semi-tensor product of matrices and the real vector representation of a quaternion matrix to find the least squares lower (upper) triangular Toeplitz solution of (AX-XB=C), (AXB-CX^{T}D=E) and (anti)centrosymmetric solution of (AXB-CYD=E). And the expressions of the least squares lower (upper) triangular Toeplitz and (anti)centrosymmetric solution for the studied equations are derived. Additionally, the necessary and sufficient conditions for the existence of solutions and general expression of the studied equations are given. Eventually, some numerical examples are provided for showing the validity and superiority of our method.
{"title":"STP Method for Solving the Least Squares Special Solutions of Quaternion Matrix Equations","authors":"Weihua Chen, Caiqin Song","doi":"10.1007/s00006-024-01367-2","DOIUrl":"10.1007/s00006-024-01367-2","url":null,"abstract":"<div><p>In this paper, we apply the semi-tensor product of matrices and the real vector representation of a quaternion matrix to find the least squares lower (upper) triangular Toeplitz solution of <span>(AX-XB=C)</span>, <span>(AXB-CX^{T}D=E)</span> and (anti)centrosymmetric solution of <span>(AXB-CYD=E)</span>. And the expressions of the least squares lower (upper) triangular Toeplitz and (anti)centrosymmetric solution for the studied equations are derived. Additionally, the necessary and sufficient conditions for the existence of solutions and general expression of the studied equations are given. Eventually, some numerical examples are provided for showing the validity and superiority of our method.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1007/s00006-024-01365-4
Vitalii Shpakivskyi
An infinite-dimensional family of exact solutions of a three-dimensional biharmonic equation was constructed by the hypercomplex method.
用超复数法构建了一个三维双谐波方程的无穷维精确解族。
{"title":"Construction of an Infinite-Dimensional Family of Exact Solutions of a Three-Dimensional Biharmonic Equation by the Hypercomplex Method","authors":"Vitalii Shpakivskyi","doi":"10.1007/s00006-024-01365-4","DOIUrl":"10.1007/s00006-024-01365-4","url":null,"abstract":"<div><p>An infinite-dimensional family of exact solutions of a three-dimensional biharmonic equation was constructed by the hypercomplex method.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142694783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1007/s00006-024-01366-3
Zhuo-Heng He, Ting-Ting Liu, Xiang-Xiang Wang
In this paper, we investigate the eigenvalues of quaternion tensors under Einstein Product and their applications in color video processing. We present the Ger(check{s})gorin theorem for quaternion tensors. Furthermore, we have executed some experiments to validate the efficacy of our proposed theoretical framework and algorithms. Finally, we contemplate the application of this methodology in color video compression, in which the reconstruction of an approximate original image is achieved by computing a limited number of the largest eigenvalues, yielding a favorable outcome. In summary, by utilizing block tensors in its iterations, this method converges more rapidly to the desired eigenvalues and eigentensors, which significantly reduces the time required for videos compression.
{"title":"Eigenvalues of Quaternion Tensors: Properties, Algorithms and Applications","authors":"Zhuo-Heng He, Ting-Ting Liu, Xiang-Xiang Wang","doi":"10.1007/s00006-024-01366-3","DOIUrl":"10.1007/s00006-024-01366-3","url":null,"abstract":"<div><p>In this paper, we investigate the eigenvalues of quaternion tensors under Einstein Product and their applications in color video processing. We present the Ger<span>(check{s})</span>gorin theorem for quaternion tensors. Furthermore, we have executed some experiments to validate the efficacy of our proposed theoretical framework and algorithms. Finally, we contemplate the application of this methodology in color video compression, in which the reconstruction of an approximate original image is achieved by computing a limited number of the largest eigenvalues, yielding a favorable outcome. In summary, by utilizing block tensors in its iterations, this method converges more rapidly to the desired eigenvalues and eigentensors, which significantly reduces the time required for videos compression.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"35 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142690705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}