|  Quaternions | 
In General
  > s.a. examples of lie groups [SO(4)]; SU(2).
  * Idea: Elements of an associative but non-commutative algebra.
  * Notation: May be written as ordered pairs of complex numbers, or as
\(\mathbb H\) = {a + i b + j c + k d | a, b, c, d ∈ \(\mathbb R\)} ,
    with i2 = j2 =
    k2 = −1, i ·  j = − j ·
    i = k and cyclic permutations; i, j, k can be represented using Pauli matrices by
    iτ1, iτ2,
    and iτ3, respectively.
  * Relationships: The unit quaternions
    are isomorphic to SU(2), topologically S3.
  @ Textbooks: Conway & Smith 03;
    Morais et al 14 [real quaternionic calculus, IIb].
  @ General references: Aslaksen MI(96) [matrix determinants];
    Kravchenko et al in(01)mp [quaternionic Riccati equation];
    De Leo et al JMP(02)mp [eigenvalue problems];
    De Leo & Ducati JMP(03)mp [quaternionic differential equations];
    Staley EJP(10) [and the Dirac belt trick for spinors and rotations];
    Colombo & Sabadini JGP(10) [functional calculus];
    Familton a1504 [history];
    Borsten & Marrani CQG(17)
      [6-algebra Freudenthal–Rosenfeld–Tits magic square].
  @ Biquaternions: Liu mp/01;
    Kassandrov & Rizcallah G&C(16)-a1612 [biquaternion algebra on a curved manifold].
  @ Other generalizations:
    Raptis mp/01 [graded, deformed];
    Volkov a1006 [ternary quaternions].
  > Online resources:
    see Wikipedia page.
Applications
  * Idea:
    Quaternions are used to describe rigid body rotations.
  @ And rotations, dynamics:
    Graf a0811 [and dynamics, introduction];
    Delphenich a1205 [use to representat physical motions].
  @ Quaternionic quantum mechanics: Adler 95;
    Adler JMP(96)ht [projective group representations];
    Brumby & Joshi CSF(96)qp;
    Horwitz FP(96)qp;
    Maia ht/99 [spin];
    De Leo & Ducati JMP(01)mp/00;
    Maia & Bezerra IJTP(01)ht [geometric phase];
    De Leo & Ducati JMP(06)mp [diffusion by potential step],
    JMP(07)-a0706 [wave packet behavior];
    de Melo & Pimentel AACA(10)-a0809-conf [variational formulation];
    McKague a0911 [non-local boxes];
    De Leo et al JMP(10)-a1012 [barrier transmission coefficients];
    Baez FP(12)-a1101;
    Graydon FP(13)-a1103 [reduced to ordinary quantum formalism];
    Muraleetharan & Thirulogasanthar JMP(15)-a1406 [coherent state quantization];
    Giardino a1706 [solutions];
    Moretti & Oppio RVMP(19)-a1709 [Poincaré symmetry and reduction to ordinary quantum theory];
    Giardino a1803 [in real Hilbert space];
    Steinberg et al a2001;
    > s.a. modified quantum theory [supersymmetric];
      Squeezed States.
  @ Dirac fields, spinors:
    De Leo & Rodrigues IJTP(98),
    IJTP(98) [Dirac electrons];
    Arbab IJLEO(17)-a1301 [Maxwell-like equations from quaternionic Dirac equation];
    Giardino FP(16)-a1504 [in a square box];
    Bolokhov IJMPA(19)-a1712 [wave functions with spin].
  @ Field theory: De Leo IJTP(96)ht/95 [guts];
    Vandoren ht/00-conf [Yang-Mills instantons];
    Maia et al FP(09)-a0809 [and quantum gravity];
    Sachs 10 [unified field theory and cosmology];
    Giardino & Teotônio-Sobrinho MPLA(13)-a1211 [non-associative scalar field theory];
    Peña & Bory a2007,
    Giardino MPLA-a2010 [electrodynamics];
    > s.a. klein-gordon fields.
  @ Cosmology: Misner in(94) [mixmaster universe];
    Brumby et al PLB(97) [dark matter];
    Majerník GRG(04)ap/03,
    GRG(03) [dark energy].
  @ Other physics:
    Robinson JMP(91) [4D conformal structure];
    Lambek MI(95);
    De Leo & Ducati IJTP(99)ht [general];
    Gsponer  & Hurni mp/02-conf [general],
    mp/05,
    mp/05 [bibliography];
    Schwartz JMP(06)ht,
    JMP(07)ht [wave equation];
    Konno QSMF-a1412 [quaternion walks].
  > In physics: see modified quantum mechanics;
    modified quantum field theories; quantum oscillators;
    special relativity; spinors; spin-3/2
    field theories.
  > Online resources on quaternions and spatial rotations:
    see Noel Hughes site [and attitude description, kinematics and dynamics];
    Wikipedia page.
 main page
  – abbreviations
  – journals – comments
  – other sites – acknowledgements
  send feedback and suggestions to bombelli at olemiss.edu – modified 24 may 2021