Exponentials of Cliffors: Hyperbolic, Null, and Circular Functions

The exponential of a cliffor \hat A is defined as

(1)\qquad e^{\hat A}=1 + \hat A+\frac{\hat A^2}{2!}+\frac{\hat A^3}{3!}+\frac{\hat A^4}{4!}.

If we assume that \hat A^2 is a scalar, then by the law of trichotomy, one and only one of the following cases is true:

(2a)\qquad e^{\hat A}=\cosh |\hat A|+\frac{\hat A}{|\hat A|}\sinh|\hat A|, \quad |\hat A|^2>0
(2b)\qquad e^{\hat A}=1+\hat A,\quad |\hat A|^2=0
(2c)\qquad e^{\hat A}=\cos |\hat A|+\frac{\hat A}{|\hat A|}\sin|\hat A|, \quad |\hat A|^2<0.

Here,

(3)\qquad |\hat A|=\sqrt{|\hat A^2|}

and

(4a)\qquad\cosh|\hat A|=1+\frac{|\hat A|^2}{2!}+\frac{|\hat A|^4}{4!}+\ldots

(4b)\qquad\sinh|\hat A|=|\hat A|+\frac{|\hat A|^3}{3!}+\frac{|\hat A|^5}{5!}+\ldots

(4c)\qquad\cos|\hat A|=1-\frac{|\hat A|^2}{2!}+\frac{|\hat A|^4}{4!}-\ldots

(4d)\qquad\sin|\hat A|=|\hat A|-\frac{|\hat A|^3}{3!}+\frac{|\hat A|^5}{5!}-\ldots.

Let \hat B be another spatial cliffor. If we decompose \hat B as

(5)\qquad \hat B=\hat B_\parallel+\hat B_\perp,

where \hat B_\parallel and \hat B_\perp are the components of \hat B that commute and anticommute with \hat A,

(6a)\qquad \hat B_\parallel\hat A=\hat A\hat B_\parallel,
(6b)\qquad \hat B_\perp\hat A=-\hat A\hat B_\perp.

From the definition of the exponential of \hat A in Eqs. (2a) to (2c), we can easily see that

(7a)\qquad\hat B_\parallel e^{\hat A}=e^{\hat A}\hat B_\parallel,
(7b)\qquad\hat B_\perp e^{\hat A}=e^{-\hat A}\hat B_\perp.

That is, only the component of \hat B that anticommutes with \hat A flips the sign of e^{\hat A}; the component \hat B that commutes with \hat A leaves the exponential e^{\hat A} unchaged after a reordering of the factors.

About Quirino M. Sugon Jr
Theoretical Physicist in Manila Observatory

One Response to Exponentials of Cliffors: Hyperbolic, Null, and Circular Functions

  1. HaugTeele says:

    Oh my god enjoyed reading your post. I added your feed to my blogreader.

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