It is just amazing that both of the mean hitting time and the cover time of a random walk on a finite graph, in which the
vertex visited next is selected from the adjacent vertices at random with the same probability, are bounded by
O(
n
3) for any undirected graph with order
n, despite of the lack of global topological information. Thus a natural guess is that a better transition matrix is designable
if more topological information is available. For any undirected connected graph
G = (
V,E), let
P(
β) = (
p
uv
(β)
)
u,v∈V be a transition matrix defined by
|
$
p_{uv}^{\left( \beta \right)} = \frac{{\exp \left[ { - \beta U\left( {u,v} \right)} \right]}}
{{\sum _{w \in N\left( u \right)} \exp \left[ { - \beta U\left( {u,w} \right)} \right]}}foru \in V,v \in N\left( u \right),
$
p_{uv}^{\left( \beta \right)} = \frac{{\exp \left[ { - \beta U\left( {u,v} \right)} \right]}}
{{\sum _{w \in N\left( u \right)} \exp \left[ { - \beta U\left( {u,w} \right)} \right]}}foru \in V,v \in N\left( u \right),
|
where
β is a real number,
N(
u) is the set of vertices adjacent to a vertex
u, deg(
u) = |
N(
u)|, and
U(
•, •) is a potential function defined as
U(
u, v) = log (max {deg(
u), deg(
v)}) for
u ∈ V, v ∈ N(
u). In this paper, we show that for any undirected graph with order
n, the cover time and the mean hitting time with respect to
P
(1) are bounded by
O(
n
2 log
n) and
O(
n
2), respectively. We further show that
P
(1) is best possible with respect to the mean hitting time, in the sense that the mean hitting time of a path graph of order
n, with respect to
any transition matrix, is
Ω (
n
2).