http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.108.573 Katis, Sabadini, Walters, [2002] "Feedback, trace and fixed-point semantics"
> a monoidal category in which the only arrows are identities is, ignoring the arrows, exactly a monoid structure on the objects, whereas a compact closed category with only identity arrows is an Abelian group. The notion of traced monoidal category in this special case turns out to be cancellative monoid.
> a monoidal category in which the only arrows are identities is, ignoring the arrows, exactly a monoid structure on the objects, whereas a compact closed category with only identity arrows is an Abelian group. The notion of traced monoidal category in this special case turns out to be cancellative monoid.