Explicit criteria for several types of ergodicity

The explicit criteria for several types of ergodicity of one-dimensional diffusions or birth-death processes have been found out recently in a surprisingly short period. One of the criteria is for exponential ergodicity of birth-death processes. This problem has been opened for a long time in the study of Markov chains. The survey article explains in details the idea which leads to solve the problem just mentioned. It is interesting that the problem is connected with several branches of mathematics. Some open problems for the further study are also proposed.