Add ones vectors

Author: HengchengZhang

lectures/eigen_II.md

@@ -395,6 +395,8 @@ In the {ref}`exercise<mc1_ex_1>`, we stated that the convergence rate is determi
 
 This can be proven using what we have learned here.
 
+Please note that we use $\mathbb{1}$ for a vector of ones in this lecture.
+
 With Markov model $M$ with state space $S$ and transition matrix $P$, we can write $P^t$ as
 
 $$

lectures/markov_chains_II.md

@@ -209,6 +209,8 @@ Theorem 5.2 of {cite}`haggstrom2002finite`.
 (ergodicity)=
 ## Ergodicity
 
+Please note that we use $\mathbb{1}$ for a vector of ones in this lecture.
+
 Under irreducibility, yet another important result obtains:
 
 ````{prf:theorem}