Bivector (complex)
In mathematics, a bivector is the vector part of a biquaternion. For biquaternion, w is called the biscalar and is its bivector part. The coordinates w, x, y, z are complex numbers with imaginary unit h:
A bivector may be written as the sum of real and imaginary parts:
where and are vectors.
Thus the bivector
The Lie algebra of the Lorentz group is expressed by bivectors. In particular, if r1 and r2 are right versors so that, then the biquaternion curve traces over and over the unit circle in the plane Such a circle corresponds to the space rotation parameters of the Lorentz group.
Now, and the biquaternion curve is a unit hyperbola in the plane The spacetime transformations in the Lorentz group that lead to FitzGerald contractions and time dilation depend on a hyperbolic angle parameter. In the words of Ronald Shaw, "Bivectors are logarithms of Lorentz transformations."
The commutator product of this Lie algebra is just twice the cross product on R3, for instance,, which is twice.
As Shaw wrote in 1970:
William Rowan Hamilton coined both the terms vector and bivector. The first term was named with quaternions, and the second about a decade later, as in Lectures on Quaternions. The popular text Vector Analysis used the term.
Given a bivector, the ellipse for which r1 and r2 are a pair of conjugate semi-diameters is called the directional ellipse of the bivector r.
In the standard linear representation of biquaternions as 2 × 2 complex matrices acting on the complex plane with basis
The conjugate transpose of this matrix corresponds to −q, so the representation of bivector q is a skew-Hermitian matrix.
Ludwik Silberstein studied a complexified electromagnetic field, where there are three components, each a complex number, known as the Riemann-Silberstein vector.
"Bivectors help describe elliptically polarized homogeneous and inhomogeneous plane waves – one vector for direction of propagation, one for amplitude."
