  There exists the Krichever map from the set of quintets (C,p,F,t,e) (where C
is an integral and complete algebraic curve, p a smooth rational point, F a
rank 2 torsion free coherent sheaf on C, t a local formal parameter in p and e
a formal trivialization of F around p) to the infinite Grassmanian of $k((z))
\oplus k((z))$. We describe the images of quintets with (semi)stable sheaves F
in terms of Plucker coordinates and get some analog of GIT Hilbert-Mumford
numerical criterion with respect to actions of some 1-parametric subgroups of
the group $SL(2,k[[z]])$ on the determinant bundle of the infinite Grassmanian.
