DOCSLIB.ORG

Singular Value Decomposition of Quaternion Matrices

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Singular Value Decomposition of Quaternion Matrices Signal Processing 84 (2004) 1177–1199 www.elsevier.com/locate/sigpro Singular value decomposition ofquaternion matrices: a new tool for vector-sensor signal processing Nicolas Le Bihan∗,JÃerˆome Mars Laboratoire des Images et des Signaux, ENSIEG, CNRS UMR 5083, 961Rue de la Houille Blanche, Domaine Universitaire, B.P. 46, 38402 Saint Martin d’Heres Cedex, France Received 31 May 2002; received in revised form 30 October 2003 Abstract We present a new approach for vector-sensor signal modelling and processing, based on the use of quaternion algebra. We introduce the concept ofquaternionic signal and give some primary tools to characterize it. We then study the problem ofvector-sensor array signals, and introduce a subspace method forwave separation on such arrays. For this purpose, we expose the extension ofthe Singular Value Decomposition (SVD) algorithm to the ÿeld ofquaternions. We discuss in more details Singular Value Decomposition for matrices of Quaternions (SVDQ) and linear algebra over quaternions ÿeld. The SVDQ allows to calculate the best rank- approximation ofa quaternion matrix and can be used in subspace method for wave separation over vector-sensor array. As the SVDQ takes into account the relationship between components, we show that SVDQ is more e>cient than classical SVD in polarized wave separation problem. ? 2004 Elsevier B.V. All rights reserved. Keywords: Vector-sensor array; Quaternion model for vector-sensor signal; Quaternion matrix algebra; Singular Value Decomposition of Quaternion matrix (SVDQ); Subspace method over quaternion ÿeld; Polarized wave separation 1. Introduction geophones in the case ofelastic waves. Sensors are po- sitioned close together and record vibrations in three Vector-sensor signal processing concerns many orthogonal directions. A schematic representation of areas such as acoustic [25], seismic [1,18], propagation and recording ofpolarized waves using communications [2,16] and electromagnetics [24,25]. vector-sensor array is presented in Fig. 1. The use of A vector-sensor is generally composed ofthree multicomponent sensors allows to recover polariza- components which record three-dimensional (3D) tion ofthe received waves. This physical information vibrations propagating through the medium. The is helpful in path recovering and waves identiÿcation components ofa vector-sensor are, in fact,dipoles or classiÿcation. Classical approaches in vector-sensor in the case ofelectromagnetic waves and directional signal processing propose to concatenate the compo- nents into a long vector before processing [1,24,25]. In this paper, we propose a diHerent approach to process vector-sensor signals, based on a quaternionic model. ∗ Corresponding author. Tel.: +33-4-76-82-64-86; fax: +33-4-76-82-63-84. A polarized signal, obtained by recording a polar- E-mail address: [email protected] (N. Le Bihan). ized wave using a vector-sensor, is a signal which 0165-1684/$ - see front matter ? 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.sigpro.2004.04.001 1178 N. Le Bihan, J. Mars / Signal Processing 84 (2004) 1177–1199 Vector sensors one-dimensional (1D) signal by means ofquaternion z z z vectors, and the bidimensional (2D) signals by means y y y Source ofquaternion matrices. We propose a new model for x x x Wave fronts vector-sensor array signals. This model allows us to manipulate polarized signals and to include polariza- tion property directly in the processing. We also intro- duce the mixture model for the polarized wave sepa- ration technique presented next. Section 5 is devoted to introduction ofa new subspace method forwave Fig. 1. Schematic representation ofa vector-sensor array during a separation on vector-sensor arrays based on SVDQ. polarized seismic wave acquisition. Its e>ciency is then evaluated on synthetic polar- ized dataset in Section 6. Conclusions are given in Section 7. samples live in 3D space (in three components vector-sensor case). We deÿne the quaternionic signal to be a time series with samples being 2. Quaternions quaternions. The three components ofthe signal are placed into the imaginary parts ofthe quater- Quaternions are an extension ofcomplex numbers nion. In this case the possibly non-linear rela- from the 2D plane to the 3D space (as well as 4D tions between them are kept unchanged. This is space) and form one of the four existing division alge- not the case when using long-vector approach bra (real R, complex C, quaternions H and octonions as this model assume intrinsically that only lin- O). Firstly discovered by Sir Hamilton [12] in 1843, ear relations exist between components. This they can be regarded as a special case of hypercom- motivates the introduction ofquaternions to model plex numbers systems [17]. Quaternion algebra is also vector-sensor signals. The quaternionic signal model + the even CliHord algebra Cl3 [21]. allows then to develop new tools for vector-sensor Quaternions are mostly used in computer vision be- signals, based on quaternion algebra. cause oftheir ability to represent rotations in 3D and We concentrate in this paper on the presentation 4D spaces. In fact, a quaternion can represent any ro- ofthe extension ofa classical and very usefultool tation ofthe rotation group SO(3). Also, two quater- in numerical signal processing: the Singular Value nions can represent any rotation from the group of Decomposition (SVD). We present the extension of rotations SO(4) [21]. Real and complex numbers are SVD to the quaternion ÿeld and we propose a new special cases ofquaternions (i.e. R ⊂ C ⊂ H). simple subspace method for vector-sensor signal pro- We now give the deÿnition ofquaternions and cessing. This new approach (that takes into account introduce diHerent notations for them. Then we relationship between components) is applied on some brieMy introduce some basic properties. Interested simulated data. reader may ÿnd some more complete material in The paper is organized as follows. In Section 2,we [5,10,12,13,17,21]. give a briefrecall on quaternions and some oftheir properties. In Section 3, a review ofsome quater- nion linear matrix algebra theorems is presented, as 2.1. Deÿnition well as a presentation ofthe isomorphism between quaternion and complex ÿelds. Using this isomor- A quaternion q is an element ofthe 4D normed phism, quaternion matrix operations can be computed algebra over the real number with basis {1; i; j; k}. by means ofclassical complex matrix computation al- So, q has a real part and three imaginary parts: gorithms. Particular attention is paid to the extension q = a + bi + cj + dk; (1) ofthe SVD to matrices with quaternions entries, called SVDQ. In Section 4, using deÿnition ofright Hilbert where a; b; c; d ∈ R, and i; j; k are imaginary units. space from Section 1, we can study the quaternion a is called the real part and q − a the vector part. N. Le Bihan, J. Mars / Signal Processing 84 (2004) 1177–1199 1179 The multiplication rules between the three imaginary where and are respectively the azimuth and eleva- numbers are: tion angles that deÿne the position of in the 3D space. The polar notation will be used in the quaternion i2 = j2 = k2 = ijk = −1; model for vector signals in Section 4. ij = −ji = k; 2.2. Properties ki = −ik = j; jk = −kj = i: (2) We now give some properties ofquaternions. In- terested reader will ÿnd an extensive list ofquater- Note that the multiplication ofquaternions is not com- nions properties in [12,13,17,37]. We focus here on mutative, and this is due to the relations between the properties that we need in our work. 1 the three imaginary parts. Several notations exist The conjugate ofa quaternion, Oq, is deÿned as for quaternions [5,10,12,13,28]. A quaternion q can uniquely be expressed as qO = a − bi − cj − dk: (6) q = + ÿj; (3) A pure quaternion is a quaternion with a null real where = a + bi and ÿ = c + di ∈ C. This is cur- part (a = 0). Quaternions with non-null real parts are rently known as the Cayley–Dickson notation. can sometimes called full quaternions. be seen as the projection of q on the complex plane The norm ofa quaternion is [15]. We will later use the Cayley–Dickson notation |q| = qqO = qqO = a2 + b2 + c2 + d2: (7) for quaternion matrix processing. It is well known that the Euler formula also general- q is called a unit quaternion ifits norm is 1. The izes to quaternion [13]. This allows to interpret quater- inverse ofa quaternion is nions in terms ofmodulus and phase. Any quaternion qO q−1 = : (8) q = a + bi + cj + dk can thus be written as 2 |q| 2 2 2 2 = a + b + c + d ; Multiplication ofquaternions is not commutative. bi + cj + dk Given two quaternions q and q , we have = √ ; 1 2  2 2 2 q = e with b + c + d (4) q q = q q : (9) √ 1 2 2 1 2 2 2 b + c + d  = arctan : This property involves the possible deÿnition oftwo a kinds ofvector spaces over H. In order to study signals In this polar formulation, is the modulus of q, is a with values in H, we now give some details on the pure unitary quaternion (see Section 2.2 for deÿnition) deÿnition ofHilbert spaces over the quaternion ÿeld. sometimes called eigenaxis [28] and  is the angle This deÿnition is necessary for validation of the model (or eigenangle [28]) between the real part and the 3D that we propose for vector signals in Section 4. imaginary (or vector) part. This can be rewritten in a trigonometric version as 2.3. Quaternion Hilbert space e  = (cos  + sin Â) Here we will consider right vector spaces over H. = (cos  + sin  cos sin i As said before, H is a division algebra, and HN can be seen as a vector space ofdimension N over H.
Load more

Recommended publications
  • Matrix Groups for Undergraduates Second Edition Kristopher Tapp
    STUDENT MATHEMATICAL LIBRARY Volume 79 Matrix Groups for Undergraduates Second Edition Kristopher Tapp https://doi.org/10.1090//stml/079 Matrix Groups for Undergraduates Second Edition STUDENT MATHEMATICAL LIBRARY Volume 79 Matrix Groups for Undergraduates Second Edition Kristopher Tapp Providence, Rhode Island Editorial Board Satyan L. Devadoss John Stillwell (Chair) Erica Flapan Serge Tabachnikov 2010 Mathematics Subject Classification. Primary 20-02, 20G20; Secondary 20C05, 22E15. For additional information and updates on this book, visit www.ams.org/bookpages/stml-79 Library of Congress Cataloging-in-Publication Data Names: Tapp, Kristopher, 1971– Title: Matrix groups for undergraduates / Kristopher Tapp. Description: Second edition. — Providence, Rhode Island : American Mathe- matical Society, [2016] — Series: Student mathematical library ; volume 79 — Includes bibliographical references and index. Identifiers: LCCN 2015038141 — ISBN 9781470427221 (alk. paper) Subjects: LCSH: Matrix groups. — Linear algebraic groups. — Compact groups. — Lie groups. — AMS: Group theory and generalizations – Research exposition (monographs, survey articles). msc — Group theory and generalizations – Linear algebraic groups and related topics – Linear algebraic groups over the reals, the complexes, the quaternions. msc — Group theory and generalizations – Repre- sentation theory of groups – Group rings of finite groups and their modules. msc — Topological groups, Lie groups – Lie groups – General properties and structure of real Lie groups. msc Classification: LCC QA184.2 .T37 2016 — DDC 512/.2–dc23 LC record available at http://lccn.loc.gov/2015038141 Copying and reprinting. Individual readers of this publication, and nonprofit libraries acting for them, are permitted to make fair use of the material, such as to copy select pages for use in teaching or research. Permission is granted to quote brief passages from this publication in reviews, provided the customary acknowledgment of the source is given.
    [Show full text]
  • On the Solutions of Linear Matrix Quaternionic Equations and Their Systems
    Mathematica Aeterna, Vol. 6, 2016, no. 6, 907 - 921 On The Solutions of Linear Matrix Quaternionic Equations and Their Systems Ahmet Ipek_ Department of Mathematics Faculty of Kamil Ozda˘gScience¨ Karamano˘gluMehmetbey University Karaman, Turkey [email protected] Cennet Bolat C¸imen Ankara Chamber of Industry 1st Organized Industrial Zone Vocational School Hacettepe University Ankara, Turkey [email protected] Abstract In this paper, our main aim is to investigate the solvability, exis- tence of unique solution, closed-form solutions of some linear matrix quaternion equations with one unknown and of their systems with two unknowns. By means of the arithmetic operations on matrix quater- nions, the linear matrix quaternion equations that is considered herein could be converted into four classical real linear equations, the solu- tions of the linear matrix quaternion equations are derived by solving four classical real linear equations based on the inverses and general- ized inverses of matrices. Also, efficiency and accuracy of the presented method are shown by several examples. Mathematics Subject Classification: 11R52; 15A30 Keywords: The systems of equations; Quaternions; Quaternionic Sys- tems. 1 Introduction The quaternion and quaternion matrices play a role in computer science, quan- tum physics, signal and color image processing, and so on (e.g., [1, 17, 22]. 908 Ahmet Ipek_ and Cennet Bolat C¸imen General properties of quaternion matrices can be found in [29]. Linear matrix equations are often encountered in many areas of computa- tional mathematics, control and system theory. In the past several decades, solving matrix equations has been a hot topic in the linear algebraic field (see, for example, [2, 3, 12, 18, 19, 21 and 30]).
    [Show full text]
  • Perturbation Analysis of Matrices Over a Quaternion Division Algebra∗
    Electronic Transactions on Numerical Analysis. Volume 54, pp. 128–149, 2021. ETNA Kent State University and Copyright © 2021, Kent State University. Johann Radon Institute (RICAM) ISSN 1068–9613. DOI: 10.1553/etna_vol54s128 PERTURBATION ANALYSIS OF MATRICES OVER A QUATERNION DIVISION ALGEBRA∗ SK. SAFIQUE AHMADy, ISTKHAR ALIz, AND IVAN SLAPNICARˇ x Abstract. In this paper, we present the concept of perturbation bounds for the right eigenvalues of a quaternionic matrix. In particular, a Bauer-Fike-type theorem for the right eigenvalues of a diagonalizable quaternionic matrix is derived. In addition, perturbations of a quaternionic matrix are discussed via a block-diagonal decomposition and the Jordan canonical form of a quaternionic matrix. The location of the standard right eigenvalues of a quaternionic matrix and a sufficient condition for the stability of a perturbed quaternionic matrix are given. As an application, perturbation bounds for the zeros of quaternionic polynomials are derived. Finally, we give numerical examples to illustrate our results. Key words. quaternionic matrices, left eigenvalues, right eigenvalues, quaternionic polynomials, Bauer-Fike theorem, quaternionic companion matrices, quaternionic matrix norms AMS subject classifications. 15A18, 15A66 1. Introduction. The goal of this paper is the derivation of a Bauer-Fike-type theorem for the right eigenvalues and a perturbation analysis for quaternionic matrices, as well as a specification of the location of the right eigenvalues of a perturbed quaternionic matrix and perturbation bounds for the zeros of quaternionic polynomials. The Bauer-Fike theorem is a standard result in the perturbation theory for diagonalizable matrices over the complex −1 field. The theorem states that if A 2 Mn(C) is a diagonalizable matrix, with A = XDX , and A + E is a perturbed matrix, then an upper bound for the distance between a point µ 2 Λ(A + E) and the spectrum Λ(A) is given by [4] (1.1) min jµ − λj ≤ κ(X)kEk: λ2Λ(A) Here, κ(X) = kXkkX−1k is the condition number of the matrix X.
    [Show full text]
  • Quaternions and Quantum Theory
    Quaternions and Quantum Theory by Matthew A. Graydon A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Science in Physics Waterloo, Ontario, Canada, 2011 c Matthew A. Graydon 2011 I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Abstract The orthodox formulation of quantum theory invokes the mathematical apparatus of complex Hilbert space. In this thesis, we consider a quaternionic quantum formalism for the description of quantum states, quantum channels, and quantum measurements. We prove that probabilities for outcomes of quaternionic quantum measurements arise from canonical inner products of the corresponding quaternionic quantum effects and a unique quaternionic quantum state. We embed quaternionic quantum theory into the framework of usual complex quantum information theory. We prove that quaternionic quantum measurements can be simulated by usual complex positive operator valued measures. Furthermore, we prove that quaternionic quantum channels can be simulated by completely positive trace preserving maps on complex quantum states. We also derive a lower bound on an orthonormality measure for sets of positive semi-definite quaternionic linear operators. We prove that sets of operators saturating the aforementioned lower bound facilitate a reconciliation of quaternionic quantum theory with a generalized Quantum Bayesian framework for reconstructing quantum state spaces. This thesis is an extension of work found in [42]. iii Acknowledgements First and foremost, I would like to deeply thank my supervisor, Dr.
    [Show full text]
  • Arxiv:Math/0206211V1 [Math.QA] 20 Jun 2002 Xml.Te a Ewitna Ai Fplnmasin Polynomials of Ratio a As Written Be Can They Example
    QUATERNIONIC QUASIDETERMINANTS AND DETERMINANTS Israel Gelfand, Vladimir Retakh, Robert Lee Wilson Introduction Quasideterminants of noncommutative matrices introduced in [GR, GR1] have proved to be a powerfull tool in basic problems of noncommutative algebra and geometry (see [GR, GR1-GR4, GKLLRT, GV, EGR, EGR1, ER,KL, KLT, LST, Mo, Mo1, P, RS, RRV, Rsh, Sch]). In general, the quasideterminants of matrix A =(aij) are rational functions in (aij)’s. The minimal number of successive inver- sions required to express an rational function is called the height of this function. The ”inversion height” is an important invariant showing a degree of ”noncommu- tativity”. In general, the height of the quasideterminants of matrices of order n equals n−1 (see [Re]). Quasideterminants are most useful when, as in commutative case, their height is less or equal to 1. Such examples include quantum matrices and their generalizations, matrices of differential operators, etc. (see [GR, GR1-GR4, ER]). Quasideterminants of quaternionic matrices A = (aij) provide a closely related example. They can be written as a ratio of polynomials in aij’s and their conju- gates. In fact, our Theorem 3.3 shows that any quasideterminant of A is a sum of monomials in the aij’s and thea ¯ij’s with real coefficients. The theory of quasideterminants leads to a natural definition of determinants of square matrices over noncommutative rings. There is a long history of attempts to develop such a theory. These works have resulted in a number of useful generalizations of determinants to special classes arXiv:math/0206211v1 [math.QA] 20 Jun 2002 of noncommutative rings, e.g.
    [Show full text]
  • Algebraic Tools for the Study of Quaternionic Behavioral Systems
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repositório Institucional da Universidade de Aveiro Algebraic tools for the study of quaternionic behavioral systems Ricardo Pereira,∗ Paula Rocha and Paolo Vettori Department of Mathematics University of Aveiro {ricardo, procha, pvettori}@mat.ua.pt Abstract In this paper we study behavioral systems whose trajectories are given as solutions of quaternionic difference equations. As happens in the commutative case, it turns out that quaternionic polynomial matrices play an important role in this context. Therefore we pay special attention to such matrices and derive new results concerning their Smith form. Based on these results, we obtain a characterization of system theoretic properties such as controllability and stability of a quaternionic behavior. 1 Introduction The behavioral approach to dynamical systems, introduced by J. C. Willems [15, 16] in the eighties, considers as the main object of study in a system the set of all the trajectories which are compatible with its laws, known as the system behavior. Whereas the classical approaches start by dividing the tra- jectories into input, output and/or state space variables, according to some predefined mathematical model (for instance, the input-output or the state space model), the point of view of the behavioral approach is rather innov- ative. One looks at the set of trajectories without imposing any structure, i.e., without speaking, at an early stage, of inputs and outputs, of causes and effects. This point of view does not only unify the previous approaches, ∗Supported by Funda¸c˜aopara a Ciˆencia e a Tecnologia 1 fitting them within an elegant theory, but it also permits to study a larger class of dynamical systems, including situations where it is not possible or desirable to make any distinction between input and output variables.
    [Show full text]
  • Dynamical Properties of Quaternionic Behavioral Systems
    Dynamical properties of quaternionic behavioral systems Ricardo Pereira∗ and Paolo Vettori Department of Mathematics University of Aveiro {ricardo, pvettori}@mat.ua.pt Abstract In this paper we study behavioral systems whose trajectories are given as solutions of quaternionic difference equations. As happens in the commutative case, it turns out that quaternionic polynomial matrices play an important role in this context. Therefore we focus our attention on such matrices and derive new results concerning their Smith form. Based on these results, we obtain characterizations of system theoretic properties of quaternionic behaviors. 1 Introduction In the eighties, J. C. Willems introduced the rather innovative behavioral approach to dynamical systems [9, 10], which essentially consists in extracting all the knowledge about a system from its behavior, i.e., the set of its admissible trajectories. Unlike the classical approaches, in the behavioral approach one looks at the set of trajectories without imposing any structure, that is, without speaking of inputs and outputs or of causes and effects at an early stage. This point of view does not only unify the previous approaches, fitting them within an elegant theory, but it also permits to study a larger class of dynamical systems including situations where it is not possible or desirable to make any distinction between input and output variables. During the last two decades the importance of the noncommutative quaternion algebra has been widely recognized. In fact, using this algebra, phenomena occurring in areas such as electro- magnetism, quantum physics and robotics may be described by a more compact notation that leads to a higher efficiency in computational terms [2, 4].
    [Show full text]
  • Non-Commutative Linear Algebra and Plurisubharmonic Functions
    Non-commutative linear algebra and plurisubharmonic functions of quaternionic variables. Semyon Alesker Department of Mathematics, Tel Aviv University, Ramat Aviv 69978 Tel Aviv, Israel e-mail: [email protected] Abstract We remind known and establish new properties of the Dieudonn´e and Moore determinants of quaternionic matrices. Using these lin- ear algebraic results we develop a basic theory of plurisubharmonic functions of quaternionic variables. 0 Introduction. The main point of this paper is that in quaternionic algebra and analysis there exist structures which have analogues over the fields of real and complex numbers, but should reflect different phenomena. The algebraic part is discussed in Section 1. There we remind the no- arXiv:math/0104209v5 [math.CV] 9 Nov 2017 tions of the Moore and Dieudonn´edeterminants of quaternionic matrices. It turns out that (under appropriate normalization) the Dieudonn´edetermi- nant behaves exactly like the absolute value of the usual determinant of real or complex matrices from all points of view (algebraic and analytic). Let us state some of its properties discussed in more details in Subsection 1.2. Let us denote by Mn(H) the set of all quaternionic n n- matrices. The Dieudonn´e determinant D is defined on this set and takes× values in non-negative real numbers: D : M (H) R n −→ ≥0 1 (see Definition 1.2.2). Then one has the following (known) results (see The- orems 1.2.3 and 1.2.4 below and references given at the beginning of Section 1): Theorem. (i) For any complex n n- matrix X considered as quaternionic matrix × the Dieudonn´edeterminant D(X) is equal to the absolute value of the usual determinant of X.
    [Show full text]
  • Characterisation of the Standard Model Gauge Group
    SO(9) characterisation of the Standard Model gauge group Kirill Krasnov typeset. School of Mathematical Sciences, University of Nottingham, NG7 2RD, UK v3: November 2020 Abstract A recent series of works by M. Dubois-Violette, I. Todorov and S. Drenska characterised the SM gauge group GSM as the subgroup of SO(9) that, in the octonionic model of the later, preserves the split O = C C3 of the space of octonions into a copy of the complex plane plus the rest. This ⊕ description, however, proceeded via the exceptional Jordan algebras J3(O),J2(O) and in this sense remained indirect. One of the goals of this paper is to provide as explicit description as possible version once it has been copyedited and and also clarify the underlying geometry. The other goal is to emphasise the role played by different 2 complex structures in the spaces O and O . We provide a new characterisation of GSM: The group GSM is the subgroup of Spin(9) that commutes with of a certain complex structure JR in the space 2 O of Spin(9) spinors. The complex structure JR is parametrised by a choice of a unit imaginary octonion. This characterisation of GSM is essentially octonionic in the sense that JR is restrictive because octonions are non-associative. The quaternionic analog of JR is the complex structure in the space H2 of Spin(5) spinors that commutes with all Spin(5) transformations. 10.1063/5.0039941 1 Introduction This paper addresses a question that is presently unfashionable, but has a long history1: ”Why is the Standard Model gauge group what it is?” A more recent set of developments related to this question started with the paper [2], and continued in [3], [4].
    [Show full text]
  • Linear Quaternion Differential Equations: Basic Theory and Fundamental Results Arxiv:1510.02224V5 [Math.CA] 7 Sep 2017
    Linear Quaternion Differential Equations: Basic Theory and Fundamental Results Kit Ian Kou1;2∗ Yong-Hui Xia1;3 y 1. School of Mathematical Sciences, Huaqiao University, 362021, Quanzhou, Fujian, China. [email protected]; [email protected] (Y.H.Xia) 2.Department of Mathematics, Faculty of Science and Technology, University of Macau, Macau [email protected] (K. I. Kou) 3. Department of Mathematics, Zhejiang Normal University, Jinhua, 321004, China ∗Kit Ian Kou acknowledges financial support from the National Natural Science Foundation of China under Grant (No. 11401606), University of Macau (No. MYRG2015-00058-FST and No. MYRG099(Y1-L2)- FST13-KKI) and the Macao Science and Technology Development Fund (No. FDCT/094/2011/A and No. FDCT/099/2012/A3). yCorresponding author. Email: [email protected]. Yonghui Xia was supported by the National Natural Science Foundation of China under Grant (No. 11671176 and No. 11271333), Natural Science Foundation of Zhejiang Province under Grant (No. Y15A010022), Marie Curie Individual Fellowship within the European Community Framework Programme(MSCA-IF-2014-EF, ILDS - DLV-655209), the Scientific Research Funds of Huaqiao University and China Postdoctoral Science Foundation (No. 2014M562320). arXiv:1510.02224v5 [math.CA] 7 Sep 2017 1 Abstract Quaternion-valued differential equations (QDEs) is a new kind of differential equations which have many applications in physics and life sciences. The largest difference between QDEs and ODEs is the alge- braic structure. Due to the non-commutativity of the quaternion alge- bra, the algebraic structure of the solutions to the QDEs is completely different from ODEs. It is actually a right free module, not a linear vector space.
    [Show full text]
  • Quaternionic Kleinian Modular Groups and Arithmetic Hyperbolic Orbifolds Over the Quaternions
    Università degli Studi di Trieste ar Ts Archivio della ricerca – postprint Quaternionic Kleinian modular groups and arithmetic hyperbolic orbifolds over the quaternions 1 1 Juan Pablo Díaz · Alberto Verjovsky · 2 Fabio Vlacci Abstract Using the rings of Lipschitz and Hurwitz integers H(Z) and Hur(Z) in the quater- nion division algebra H, we define several Kleinian discrete subgroups of PSL(2, H).We define first a Kleinian subgroup PSL(2, L) of PSL(2, H(Z)). This group is a general- ization of the modular group PSL(2, Z). Next we define a discrete subgroup PSL(2, H) of PSL(2, H) which is obtained by using Hurwitz integers. It contains as a subgroup PSL(2, L). In analogy with the classical modular case, these groups act properly and discontinuously on the hyperbolic quaternionic half space. We exhibit fundamental domains of the actions of these groups and determine the isotropy groups of the fixed points and 1 1 describe the orb-ifold quotients HH/PSL(2, L) and HH/PSL(2, H) which are quaternionic versions of the classical modular orbifold and they are of finite volume. Finally we give a thorough study of their descriptions by Lorentz transformations in the Lorentz–Minkowski model of hyperbolic 4-space. Keywords Modular groups · Arithmetic hyperbolic 4-manifolds · 4-Orbifolds · Quaternionic hyperbolic geometry Mathematics Subject Classification (2000) Primary 20H10 · 57S30 · 11F06; Secondary 30G35 · 30F45 Dedicated to Bill Goldman on occasion of his 60th birthday. B Alberto Verjovsky [email protected] Juan Pablo Díaz [email protected] Fabio Vlacci [email protected]fi.it 1 Instituto de Matemáticas, Unidad Cuernavaca, Universidad Nacional Autónoma de México, Av.
    [Show full text]
  • Quaternionic Monge-Ampere Equations
    Quaternionic Monge-Amp`ere equations. Semyon Alesker Department of Mathematics, Tel Aviv University, Ramat Aviv 69978 Tel Aviv, Israel e-mail: [email protected] Abstract The main result of this paper is the existence and uniqueness of so- lution of the Dirichlet problem for quaternionic Monge-Amp`ere equa- tions in quaternionic strictly pseudoconvex bounded domains in Hn. We continue the study of the theory of plurisubharmonic functions of quaternionic variables started by the author at [2]. 0 Introduction. This paper is a continuation of author’s previous paper [2]. In [2] we have de- veloped the necessary algebraic technique and we have introduced and stud- ied the class of plurisubharmonic functions of quaternionic variables (this class was independently introduced also by G. Henkin [36]). The main re- sult of the present paper is the existence of a generalized solution of the Dirichlet problem for quaternionic Monge-Amp`ere equations in quaternionic strictly pseudoconvex bounded domains in Hn. The uniqueness of solution arXiv:math/0208005v4 [math.CV] 5 Jul 2016 was established in [2]. The versions of this result for real and complex Monge-Amp`ere equations were established in classical papers by A.D. Aleksandrov [1] (the real case) and E. Bedford and B. Taylor [10] (the complex case). We prove also a result on the regularity of solution in the Euclidean ball. For real Monge-Amp`ere equations this result was proved by L. Caffarelli, L. Nirenberg, and J. Spruck [14] for arbitrary strictly convex bounded domains, and for complex Monge- Amp`ere equations by L.
    [Show full text]