On the Meeting Time for Two Random Walks on a Regular Graph
  We provide an analysis of the expected meeting time of two independent random walks on a regular graph. For 1-D circle and 2-D torus graphs, we show that the expected meeting time can be expressed as the sum of the inverse of non-zero eigenvalues of a suitably defined Laplacian matrix. We also conjecture based on empirical evidence that this result holds more generally for simple random walks on arbitrary regular graphs. Further, we show that the expected meeting time for the 1-D circle of size $N$ is $\Theta(N^2)$, and for a 2-D $N \times N$ torus it is $\Theta(N^2 log N)$. 
Yizhen Zhang and Zihan Tan and Bhaskar Krishnamachari
math.PR cs.DM math.CO