Operator support
= Operator support
{title2=$\operatorname{supp}(A)$}
The <operator support> is the set of subsystems on which an operator may act nontrivially; it acts as the identity outside that set. <Unitary time evolution> can enlarge the support, while a <Lieb-Robinson bound> controls the error of replacing the evolved operator by one with smaller support. The support diameter and the number of sites in the support are different quantities.