Central algebra

An algebra with a unit element over a field, the centre of which (see Centre of a ring) coincides with the ground field. For example, the division ring of quaternions is a central algebra over the field of real numbers, but the field of complex numbers is not. The full matrix algebra over a field is a central algebra. The tensor product of a simple algebra and a central simple algebra is a simple algebra, which is central if and only if the first one is. Every automorphism of a finite-dimensional central simple algebra is inner and its dimension is the square of an integer.

References

[1]	Yu.A. Drozd, V.V. Kirichenko, "Finite-dimensional algebras" , Kiev (1980) (In Russian)
[2]	L.A. Skornyakov, "Elements of general algebra" , Moscow (1983) (In Russian)
[a1]	R.S. Peirce, "Associative algebras" , Springer (1980)
[a2]	A.A. Albert, "Structure of algebras" , Amer. Math. Soc. (1939)
[a3]	M. Deuring, "Algebren" , Springer (1935)
[a4]	I.N. Herstein, "Noncommutative rings" , Math. Assoc. Amer. (1968)
[a5]	N. Jacobson, "Structure of rings" , Amer. Math. Soc. (1956)