canonicalDivisor( R )
Compute the canonical divisor of a ring (warning, the canonical divisor is not unique, but only unique up to linear equivalence). If the IsGraded option is set to true (default false), then it will return a canonical divisor for the $Proj$ of $R$, otherwise it will return one for only the $Spec$. The graded version only works reliably for graded rings over a field (for instance, if you have a Rees algebra you will need to flatten the variables).
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Note the IsGraded option makes a difference. Consider now a non-Gorenstein singularity.
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Text This function assumes that the coefficientRing of the ambient ring is a field (or at least Gorenstein). If the coefficientRing is a more general ring, this function will produce a relative canonical divisor of the ring over its coefficientRing.
The object canonicalDivisor is a method function with options.