  The optical afterglows of the gamma ray bursts can be strongly polarized, in
principle up to tens of percents, if: (i) the afterglow is synchrotron
radiation from an ultra-relativistic blast, (ii) the blast is beamed during the
afterglow phase, i.e. the shock propagates within a narrow jet, (iii) we
observe at the right time from the right viewing angle, (iv) magnetic fields
parallel and perpendicular to the jet have different proper strengths.
