Marcelo De Martino, Alexis Langlois-Rémillard, Roy Oste
{"title":"The Double Dihedral Dunkl Total Angular Momentum Algebra","authors":"Marcelo De Martino, Alexis Langlois-Rémillard, Roy Oste","doi":"10.1007/s00006-026-01441-x","DOIUrl":"10.1007/s00006-026-01441-x","url":null,"abstract":"<div><p>The Dunkl total angular momentum algebra (TAMA) is realised as the dual partner of the orthosymplectic Lie superalgebra containing the Dunkl deformation of the Dirac operator. In this paper, we consider the case when the reflection group associated with the Dunkl operators is a product of two dihedral groups acting on a four-dimensional Euclidean space. We show that in this case there is a subalgebra of the total angular momentum algebra that admits a triangular decomposition. In analogy to the celebrated theory of semisimple Lie algebras, we use this triangular subalgebra to give precise necessary conditions that a finite-dimensional irreducible representation must obey, in terms of weights. In specific cases, which includes unitary representations, we construct a basis of weight vectors with explicit actions of all TAMA elements. Examples of these modules occur in the kernel of the Dunkl–Dirac operator in the context of deformations of Howe dual pairs.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00006-026-01441-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147829994","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}
{"title":"Complex Structure-Preserving Algorithm for LU Decomposition of Dual Quaternion Matrices and Its Application","authors":"Xiaochen Liu, Ying Li, Ruyu Tao, Jianhua Sun","doi":"10.1007/s00006-026-01446-6","DOIUrl":"10.1007/s00006-026-01446-6","url":null,"abstract":"<div><p>Dual quaternion has a wide range of applications in various fields, and the study of its matrix theory has become a hot topic in recent years. In the theoretical study of dual quaternion matrices, the <i>LU</i> decomposition plays an important role. However, due to the non-commutativity of dual quaternions, the calculation of <i>LU</i> decomposition becomes difficult. In this paper, by means of the quaternion representation of the dual quaternion matrices given by semi-tensor product of matrices and the complex representation of the quaternion matrices, we give the complex representation of the dual quaternion matrices and its properties. The complex representation we proposed greatly facilitates the simplification of computational processes. And using these properties, we propose a fast and efficient complex structure-preserving algorithm for <i>LU</i> decomposition of dual quaternion matrices. The algorithm avoids the complexity of dual quaternion operations (essentially, quaternion operations). In order to ensure the stability of the algorithm, we further give a partial pivoting dual quaternion <i>LU</i> decomposition algorithm. Based on <i>LU</i> decomposition, we also present a complex structure-preserving algorithm for <span>(LDL^H)</span> decomposition of dual quaternion Hermitian matrices. In addition, we illustrate the effectiveness of the complex structure-preserving algorithms through numerical experiments. Finally, we give the application of dual quaternion matrix <i>LU</i> decomposition in color image authentication and kinematic linear equations.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147756100","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}
{"title":"Limiting Sobolev Inequalities for k-Cauchy–Fueter Complex","authors":"Xin Luo, Sihan Ning","doi":"10.1007/s00006-026-01443-9","DOIUrl":"10.1007/s00006-026-01443-9","url":null,"abstract":"<div><p>The <i>k</i>-Cauchy–Fueter complex is the quaternionic counterpart of the Cauchy–Riemann complex in several complex variables, which plays a fundamental role in quaternionic analysis. In this work, we investigate the regularity of solutions to the non-homogeneous <i>k</i>-Cauchy–Fueter equation. Based on the Bourgain–Brezis inequalities, we extend the Limiting Sobolev inequalities to <i>k</i>-Cauchy–Fueter complex. In particular, we get the Gagliardo–Nirenberg inequality for the <i>k</i>-CF operator. In certain cases, the Hardy space <span>({mathcal {H}}^1)</span> is used in place of <span>(L^1.)</span></p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147751199","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}
Aziz Blali, Abdellah El Allaoui, Abdelkhalek El Amrani
{"title":"Extensions of Jacobson’s Lemma and Cline’s formula in the Quaternionic Setting","authors":"Aziz Blali, Abdellah El Allaoui, Abdelkhalek El Amrani","doi":"10.1007/s00006-026-01440-y","DOIUrl":"10.1007/s00006-026-01440-y","url":null,"abstract":"<div><p>Let <i>X</i> be a two-sided Banach quaternionic space and <span>(A, C, B, D: X rightarrow X)</span> be the right bounded linear operators satisfying operator equation set </p><div><div><span>$$begin{aligned} A C D=D B D ;and; D B A=A C A. end{aligned}$$</span></div></div><p>In this paper, we generalize Jacobson’s Lemma and investigate the common properties of <span>((A C)^2-2 operatorname {Re}(q) A C+|q|^2 I)</span> and <span>((B D)^2-2 operatorname {Re}(q) B D+|q|^2 I)</span> where <i>I</i> stands for the identity operator on <i>X</i> and non-zero quaternion <i>q</i>. In particular, we show that </p><div><div><span>$$ sigma _{mathcal {*}}^S(A C) backslash {0}=sigma _{mathcal {*}}^S(B D) backslash {0}, $$</span></div></div><p>where <span>(sigma _{mathcal {*}}^S(.))</span> is a distinguished part of the spherical spectrum.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642990","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}
{"title":"Riemann–Hilbert Problems for Biaxially Symmetric Null Solutions to Iterated Perturbed Dirac Equations in (mathbb {R}^{n})","authors":"Dian Zuo, Min Ku, Fuli He","doi":"10.1007/s00006-026-01444-8","DOIUrl":"10.1007/s00006-026-01444-8","url":null,"abstract":"<div><p>This work addresses Riemann–Hilbert boundary value problems (RHBVPs) for null solutions to iterated perturbed Dirac operators over biaxially symmetric domains in <span>(mathbb {R}^n)</span> with Clifford-algebra-valued variable coefficients. We first resolve the unperturbed case of poly-monogenic functions, i.e., null solutions to iterated Dirac operators, by constructing explicit solutions via a biaxially adapted Almansi-type decomposition, which decouples hierarchical structures through recursive integral operators. Then, generalizing to vector wave number-perturbed iterated Dirac operators, we extend the decomposition to manage spectral anisotropy while preserving symmetry constraints, ensuring regularity under Clifford-algebraic parameterizations. As a key application, closed-form solutions to the Schwarz problem are derived, demonstrating unified results across classical and higher-dimensional settings. The interplay of symmetry, decomposition, and perturbation theory establishes a cohesive framework for higher-order boundary value challenges in Clifford analysis.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147619692","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}
{"title":"Fourier Transform on Cayley–Dickson Algebras","authors":"Shihao Fan, Guangbin Ren","doi":"10.1007/s00006-026-01439-5","DOIUrl":"10.1007/s00006-026-01439-5","url":null,"abstract":"<div><p>We introduce the <i>Cayley–Dickson Fourier transform (CDFT)</i>, a novel framework for harmonic analysis of functions valued in the non-associative Cayley–Dickson algebras <span>( mathcal {C}_m )</span>. The central challenge lies in the failure of associativity and alternativity for <span>( m geqslant 4 )</span>, which obstructs classical Fourier analytic methods. To overcome this, we develop a two-stage approach: first, we construct the transform on real-valued Schwartz-type spaces, establishing continuity, inversion, and isometric properties; second, we extend the theory to fully <span>( mathcal {C}_m )</span>-valued functions by leveraging intrinsic algebraic structures, such as slice-wise multiplicativity and weak commutativity. Key innovations include a modified duality between differentiation and multiplication, governed by twisted sign involutions that precisely compensate for non-associative distortions, and a restricted convolution theorem for Gaussian-type functions that exploits the real scalar structure of their transforms. We prove that the CDFT admits an explicit inverse via symmetrization over coordinate reflections, acts isometrically on <span>( L^2(mathbb {R}^m, mathcal {C}_m) )</span>, and exhibits a period-four symmetry that generalizes classical Fourier periodicity. These results collectively establish the CDFT as a rigorous and structurally faithful extension of Fourier analysis to the full Cayley–Dickson hierarchy.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146230777","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}
{"title":"Bicomplex Polyholomorphic Bergman Spaces Associated with a Bicomplex Magnetic Laplacian on the Discus","authors":"Issame Ahizoune, Aiad Elgourari, Allal Ghanmi","doi":"10.1007/s00006-026-01438-6","DOIUrl":"10.1007/s00006-026-01438-6","url":null,"abstract":"<div><p>We consider a bicomplex analogue of the Landau Hamiltonian defined via its idempotent representation as a couple of the classical Landau Hamiltonians on two separate complex discs. We provide a complete characterization of its <span>(L^2)</span>-eigenspaces when acting on the so-called bicomplex <i>p</i>-Hilbert space, which next employed to explore the common eigenfunction problem associated with the magnetic bc-Laplacian and its <span>(dagger )</span>-conjugate. The corresponding eigenspaces give rise to the polyanalytic version of the bicomplex Bergman spaces for which we provide the explicit expressions for their reproducing kernels.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146196658","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}
{"title":"Construction of Exceptional Lie Algebra G2 and Non-associative Algebras Using Clifford Algebra","authors":"G. P. Wilmot","doi":"10.1007/s00006-025-01423-5","DOIUrl":"10.1007/s00006-025-01423-5","url":null,"abstract":"<div><p>This article uses Clifford algebra of positive definite signature to derive octonions and the Lie exceptional algebra <span>(textrm{G2})</span> from calibrations using <span>(mathrm{Pin(7)})</span>. This is simpler than the usual exterior algebra derivation and uncovers a subalgebra of <span>(mathrm{Spin(}7))</span> that enables <span>(textrm{G2})</span> and an invertible element used to classify six new power-associative algebras, which are found to be related to the symmetries of <span>(textrm{G2})</span> in a way that breaks the symmetry of octonions. The 4-form calibration terms of <span>(mathrm{Spin(7)})</span> are related to an ideal with three idempotents and provides a direct construction of <span>(textrm{G2})</span> for each of the 480 representations of the octonions. Clifford algebra thus provides a new construction of <span>(textrm{G2})</span> without using the Lie bracket. A calibration in 15 dimensions is shown to generate the sedenions and to include one of the power-associative algebras, a result previously found by Cawagas.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00006-025-01423-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146196673","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}
{"title":"Monoids of Compatible Bilinear Forms in Relation to Lipschitz Monoids","authors":"Jacques Helmstetter","doi":"10.1007/s00006-026-01437-7","DOIUrl":"10.1007/s00006-026-01437-7","url":null,"abstract":"<div><p>Let <i>V</i> be a vector space of finite dimension over a field <i>K</i>, and <i>Q</i> a quadratic form on <i>V</i>. A bilinear form compatible with <i>Q</i> is a bilinear form <span>(varphi )</span> defined on any subspace <i>S</i> of <i>V</i> such that <span>(varphi (s,s)=Q(s))</span> for all <span>(sin S)</span>. The bilinear forms compatible with <i>Q</i>, together with an exceptional empty element, constitute an associative and unital monoid <span>(textrm{Cbf}(V,Q))</span>. In the first part of this work, the main purpose is a surjective homomorphism from the Lipschitz monoid <span>(textrm{Lip}(V,Q))</span> onto this monoid <span>(textrm{Cbf}(V,Q))</span>. In the second part, <i>V</i> is provided with an alternating bilinear form <span>(Omega ,)</span> and some analogous properties are established for the monoid of bilinear forms compatible with <span>(Omega )</span>. When <i>K</i> is the field of real numbers, the controversy about an eventual Lipschitz monoid for <span>(Omega )</span> is recalled.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138555","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}
{"title":"The Dirac Equation from the Perspective of Quaternionic Analysis","authors":"Jürgen Bolik","doi":"10.1007/s00006-026-01436-8","DOIUrl":"10.1007/s00006-026-01436-8","url":null,"abstract":"<div><p>The Dirac equation is mapped to a first order differential equation for complex quaternionic functions to benefit from potential theory and quaternionic analysis. This method provides solutions which do not depend on particular matrix representations for Clifford algebras. We additionally deduce zero-mode solutions for the Dirac–Weyl equation, when non-vanishing vector potentials are presupposed.</p></div>","PeriodicalId":7330,"journal":{"name":"Advances in Applied Clifford Algebras","volume":"36 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00006-026-01436-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138556","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}