释义 |
QuaternionA member of a noncommutative Division Algebra first invented by William Rowan Hamilton. The quaternions are sometimes also known as Hypercomplex Numbers and denoted . While the quaternions are not commutative, they are associative.
The quaternions can be represented using complex Matrices
 | (1) |
where and are Complex Numbers, , , , and are Real, and is the Complex Conjugate of . By analogy with the Complex Numbers being representableas a sum of Real and Imaginary Parts, , a quaternion can also bewritten as a linear combination
 | (2) |
of the four matrices
(Note that here, is used to denote the Identity Matrix, not .) The matrices are closely related tothe Pauli Spin Matrices , , , combined with the Identity Matrix. From theabove definitions, it follows that
Therefore , , and are three essentially different solutions of the matrix equation
 | (10) |
which could be considered the square roots of the negative identity matrix.
In , the basis of the quaternions can be given by
The quaternions satisfy the following identities, sometimes known as Hamilton's Rules,
 | (15) |
 | (16) |
 | (17) |
 | (18) |
They have the following multiplication table.The quaternions , , , and form a non-Abelian Group of order eight(with multiplication as the group operation) known as .
The quaternions can be written in the form
 | (19) |
The conjugate quaternion is given by
 | (20) |
The sum of two quaternions is then
 | (21) |
and the product of two quaternions is
so the norm is
 | (23) |
In this notation, the quaternions are closely related to Four-Vectors.
Quaternions can be interpreted as a Scalar plus a Vector by writing
 | (24) |
where . In this notation, quaternion multiplication has the particularly simpleform
 | (25) |
Division is uniquely defined (except by zero), so quaternions form a Division Algebra. The inverse of a quaternion is given by
 | (26) |
and the norm is multiplicative
 | (27) |
In fact, the product of two quaternion norms immediately gives the Euler Four-Square Identity.
A rotation about the Unit Vector by an angle can be computed using thequaternion
 | (28) |
(Arvo 1994, Hearn and Baker 1996). The components of this quaternion are called Euler Parameters.After rotation, a point is then given by
 | (29) |
since . A concatenation of two rotations, first and then , can be computed using the identity
 | (30) |
(Goldstein 1980).See also Biquaternion, Cayley-Klein Parameters, Complex Number, Division Algebra, EulerParameters, Four-Vector, Octonion References
QuaternionsAltmann, S. L. Rotations, Quaternions, and Double Groups. Oxford, England: Clarendon Press, 1986. Arvo, J. Graphics Gems II. New York: Academic Press, pp. 351-354 and 377-380, 1994. Baker, A. L. Quaternions as the Result of Algebraic Operations. New York: Van Nostrand, 1911. Beeler, M.; Gosper, R. W.; and Schroeppel, R. HAKMEM. Cambridge, MA: MIT Artificial Intelligence Laboratory, Memo AIM-239, Item 107, Feb. 1972. Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, pp. 230-234, 1996. Crowe, M. J. A History of Vector Analysis: The Evolution of the Idea of a Vectorial System. New York: Dover, 1994. Dickson, L. E. Algebras and Their Arithmetics. New York: Dover, 1960. Du Val, P. Homographies, Quaternions, and Rotations. Oxford, England: Oxford University Press, 1964. Ebbinghaus, H. D.; Hirzebruch, F.; Hermes, H.; Prestel, A; Koecher, M.; Mainzer, M.; and Remmert, R. Numbers. New York: Springer-Verlag, 1990. Goldstein, H. Classical Mechanics, 2nd ed. Reading, MA: Addison-Wesley, p. 151, 1980. Hamilton, W. R. Lectures on Quaternions: Containing a Systematic Statement of a New Mathematical Method. Dublin: Hodges and Smith, 1853. Hamilton, W. R. Elements of Quaternions. London: Longmans, Green, 1866. Hamilton, W. R. The Mathematical Papers of Sir William Rowan Hamilton. Cambridge, England: Cambridge University Press, 1967. Hardy, A. S. Elements of Quaternions. Boston, MA: Ginn, Heath, & Co., 1881. Hardy, G. H. and Wright, E. M. An Introduction to the Theory of Numbers, 5th ed. Cambridge, England: Clarendon Press, 1965. Hearn, D. and Baker, M. P. Computer Graphics: C Version, 2nd ed. Englewood Cliffs, NJ: Prentice-Hall, pp. 419-420 and 617-618, 1996. Joly, C. J. A Manual of Quaternions. London: Macmillan, 1905. Julstrom, B. A. ``Using Real Quaternions to Represent Rotations in Three Dimensions.'' UMAP Modules in Undergraduate Mathematics and Its Applications, Module 652. Lexington, MA: COMAP, Inc., 1992. Kelland, P. and Tait, P. G. Introduction to Quaternions, 3rd ed. London: Macmillan, 1904. Nicholson, W. K. Introduction to Abstract Algebra. Boston, MA: PWS-Kent, 1993. Tait, P. G. An Elementary Treatise on Quaternions, 3rd ed., enl. Cambridge, England: Cambridge University Press, 1890. Tait, P. G. ``Quaternions.'' Encyclopædia Britannica, 9th ed. ca. 1886. ftp://ftp.netcom.com/pub/hb/hbaker/quaternion/tait/Encyc-Brit.ps.gz.
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