Solution
= Solution
With stationary flow $Q(x,y)=\pi(x)P(x,y)$, the <conductance of a Markov chain> is $\Phi(A)=Q(A,A^c)/\pi(A)$. The bottleneck ratio and isoperimetric profile are
$$
\Phi_*=\inf_{0<\pi(A)\leq1/2}\Phi(A),
\qquad
\Phi_*(r)=\inf_{0<\pi(A)\leq r}\Phi(A),
\quad0<r\leq\frac12.
$$