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Example 1.
We define the quaternions and the split quaternions and compare their multiplication tables:
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Here are the split quaternions.
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We see that the off-diagonal products in the multiplication tables are the same. For the quaternions while for the split quaternions .
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Example 2.
Various conventions can be found in the literature for the multiplication table for the octonions, differing by a labeling of the basis elements. The command AlgebraLibraryData provides 2 different conventions. For the first, the multiplication rules are defined by the formula
where the are the components of a 3-form determined by These multiplication rules are summarized using the Fano plane mnemonic:
The triple of integers lying on a straight line or circle coincide with the non-zero coefficients of .
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For the second version, the non-zero components of the 3-form are
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Both versions have split counterparts.
Example 3.
Let be a vector space with basis and let be a non-degenerate quadratic form on The Clifford algebra is the algebra generated by products of the vectors subject to the multiplication rules
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A vector space basis for the Clifford algebra is the identity and the ordered products , where . The dimension of is The default choice for the quadratic form is given by the identity matrix .
We first display the multiplication tables for
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We note that the Clifford algebras are always associative.
Here is the multiplication table for .
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Finally, we remark that the quaternions and the Clifford algebra are isomorphic.
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Example 4.
Here are the structure equations for the Jordan algebra . This is the algebra of 2 × 2 Hermitian matrices with quaternionic entries and the product
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