Slower-speed degeneration of a large deviation principle ($a_n/b_n\to \infty :I_b(x)=0\text{ at }\mu ,I_b(x)=\infty \text{ elsewhere}$)

Suppose a large deviation principle at speed $a_n$ has a good rate function with unique zero mu. At any slower speed $b_n\to \infty$ with $a_n/b_n\to \infty$, its rate is zero at mu and infinity elsewhere. On a closed set excluding mu, the positive original rate gives decay faster than every exponential at speed $b_n$. Neighborhoods of mu have probability tending to one, giving the slower-speed open-set lower bound. The new rate is good because its finite sublevel set is the singleton mu.