In discrete percolation theory, bond percolation is a percolation model on a regular point
lattice 
in 
-dimensional
Euclidean space which considers the lattice graph edges
as the relevant entities (left figure). The precise mathematical construction for
the Bernoulli percolation model version
of bond percolation is given below.
First, define the set 
of edges of 
to be the set
 |
(1)
|
and designate each edge of 
to be independently "open" with probability ![p in [0,1]](/images/equations/BondPercolation/Inline6.svg)
and closed with probability
. Next, define an open path to be
any path in 
all of whose edges are open, and define the so-called open cluster 
to be the connected component of the random subgraph of
consisting of only open edges and containing
the vertex 
.
Write 
.
The main objects of study in the bond percolation model are then the percolation
probability
 |
(2)
|
and the critical probability
 |
(3)
|
where 
is defined to be the product measure
 |
(4)
|
is the Bernoulli measure which assigns
whenever 
is closed and assigns 
when 
is open, and 
is the percolation
threshold. Bond models for which 
will have infinite connected components (i.e., percolations)
whereas those for which 
will not.
In general, bond percolation is considered less general than site percolation due to the fact that every bond model may be reformulated as a site model on a different lattice but not vice versa. Mixed percolation is considered to be a bridge between the two. Note, too, the existence of several other variants of bond percolation; for example, one could drop the assumption of independence to obtain a non-Bernoulli, dependent bond model.
