  We consider the model of random surfaces with extrinsic curvature term
embedded into 3d Euclidean lattice $Z^3$. On a 3d Euclidean lattice it has
equivalent representation in terms of transfer matrix $K(Q_{i},Q_{f})$, which
describes the propagation of loops $Q$. We study the spectrum of the transfer
matrix $K(Q_{i},Q_{f})$ on finite dimensional lattices. The renormalisation
group technique is used to investigate phase structure of the model and its
critical behaviour.
