  A connection between the response and fluctuation in general nonequilibrium
stationary states is investigated. We focus on time-symmetric quantities and
find that the fluctuation of a kind of empirical measure can be expressed with
the response of the empirical measure, current, and the time-symmetric current.
This relation is proven by using the fictitious stalling decomposition: We
decompose a single observed transition (edge in the state space) between two
microscopic states into two transitions such that one of the transitions stalls
in this stationary state. Through this trick, relations for stalling stationary
states apply to general nonequilibrium stationary states, which leads to the
desired relation.
