Inalgebra, agraded-commutative ring (also called askew-commutative ring) is agraded ring that is commutative in the graded sense; that is,homogeneous elementsx,y satisfy
where |x | and |y | denote the degrees ofx andy.
Acommutative (non-graded) ring, with trivial grading, is a basic example. For a nontrivial example, anexterior algebra is generally not acommutative ring but is agraded-commutative ring.
Acup product oncohomology satisfies the skew-commutative relation; hence, acohomology ring is graded-commutative. In fact, many examples of graded-commutative rings come fromalgebraic topology andhomological algebra.
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