<s>
In	O
statistical	O
mechanics	O
,	O
the	O
n-vector	B-Algorithm
model	I-Algorithm
or	O
O(n )	O
model	O
is	O
a	O
simple	O
system	O
of	O
interacting	O
spins	O
on	O
a	O
crystalline	O
lattice	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
H	O
.	O
Eugene	O
Stanley	O
as	O
a	O
generalization	O
of	O
the	O
Ising	O
model	O
,	O
XY	B-Algorithm
model	I-Algorithm
and	O
Heisenberg	O
model	O
.	O
</s>
<s>
In	O
the	O
n-vector	B-Algorithm
model	I-Algorithm
,	O
n-component	O
unit-length	O
classical	O
spins	O
are	O
placed	O
on	O
the	O
vertices	O
of	O
a	O
d-dimensional	O
lattice	O
.	O
</s>
<s>
The	O
Hamiltonian	O
of	O
the	O
n-vector	B-Algorithm
model	I-Algorithm
is	O
given	O
by	O
:	O
</s>
<s>
Special	O
cases	O
of	O
the	O
n-vector	B-Algorithm
model	I-Algorithm
are	O
:	O
</s>
<s>
The	O
general	O
mathematical	O
formalism	O
used	O
to	O
describe	O
and	O
solve	O
the	O
n-vector	B-Algorithm
model	I-Algorithm
and	O
certain	O
generalizations	O
are	O
developed	O
in	O
the	O
article	O
on	O
the	O
Potts	O
model	O
.	O
</s>
<s>
The	O
continuum	B-Algorithm
limit	I-Algorithm
can	O
be	O
understood	O
to	O
be	O
the	O
sigma	O
model	O
.	O
</s>
