Algebras Satisfying Identities
Ring-like structures with two binary operations and no other restrictions are a broad class, one which is too general to study. For this reason, the best-known kinds of non-associative algebras satisfy identities which simplify multiplication somewhat. These include the following identities.
In the list, x, y and z denote arbitrary elements of an algebra.
- Associative: (xy)z = x(yz).
- Commutative: xy = yx.
- Anticommutative: xy = −yx.
- Jacobi identity: (xy)z + (yz)x + (zx)y = 0.
- Jordan identity: (xy)x2 = x(yx2).
- Power associative: For all x, and any three nonnegative powers of x associate. That is if a, b and c are nonnegative powers of x, then a(bc) = (ab)c. This is equivalent to saying that xm xn = xn+m for all non-negative integers m and n.
- Alternative: (xx)y = x(xy) and (yx)x = y(xx).
- Flexible: x(yx) = (xy)x.
These properties are related by
- associative implies alternative implies power associative;
- associative implies Jordan identity implies power associative;
- Each of the properties associative, commutative, anticommutative, Jordan identity, and Jacobi identity individually imply flexible.
- For a field with characteristic not two, being both commutative and anticommutative implies the algebra is just {0}.
Read more about this topic: Non-associative Algebra
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