Using the method of transportation-information inequality introduced in
\cite{GLWY}, we establish Bernstein type's concentration inequalities for
empirical means t1∫0tg(Xs)ds where g is a unbounded
observable of the symmetric Markov process (Xt). Three approaches are
proposed : functional inequalities approach ; Lyapunov function method ; and an
approach through the Lipschitzian norm of the solution to the Poisson equation.
Several applications and examples are studied