  We study Cerenkov radiation from moving straight strings which glisse with
respect to each other in such a way that the projected intersection point moves
faster than light. To calculate this effect we develop classical perturbation
theory for the system of Nambu-Goto strings interacting with dilaton, two-form
and gravity. In the first order one encounters divergent self-action terms
which are eliminated by classical renormalization of the string tension.
Cerenkov radiation arises in the second order. It is generated by an effective
source which contains contributions localized on the strings world-sheets and
bulk contributions quadratic in the first order fields. In the
ultra-relativistic limit radiation exhibits angular peaking on the Cerenkov
cone in the forward direction of the fast string in the rest frame of another.
The radiation spectrum then extends up to high frequencies proportional to
square of the Lorentz-factor of the relative velocity. Gravitational radiation
is absent since the 1+2 space-time transverse to the straight string does not
allow for gravitons. A rough estimate of the Cerenkov radiation in the
cosmological cosmic strings network is presented.
