This article is about the object in geometric algebra. For the vector concept, see Rotor (operator).
A rotor is an object in the geometric algebra (also called Clifford algebra) of a vector space that represents a rotation about the origin.[1] The term originated with William Kingdon Clifford,[2] in showing that the quaternion algebra is just a special case of Hermann Grassmann's "theory of extension" (Ausdehnungslehre).[3] Hestenes[4] defined a rotor to be any element of a geometric algebra that can be written as the product of an even number of unit vectors and satisfies , where is the "reverse" of —that is, the product of the same vectors, but in reverse order.
^Clifford, William Kingdon (1878). "Applications of Grassmann's Extensive Algebra". American Journal of Mathematics. 1 (4): 353. doi:10.2307/2369379. JSTOR2369379.
^Grassmann, Hermann (1862). Die Ausdehnugslehre (second ed.). Berlin: T. C. F. Enslin. p. 400.
^Hestenes, David; Sobczyk, Garret (1987). Clifford Algebra to Geometric Calculus (paperback ed.). Dordrecht, Holland: D. Reidel. p. 105. Hestenes uses the notation for the reverse.