In this note we prove an anolog
of Amitsur’s theorem for central polynomials.
Theorem. Let F be an infinite field, f(x) = f(x1,⋯,xr), g(x) = g(xr+1,⋯,xs)
two noncommutative polynomials in disjoint sets of variables. Assume that
f(x1,⋯,xr) ⋅g(xr+1,⋯,xs) is central but not an identity for Fk. Then both f(x) and
g(x) are central polynomials for Fk.
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