School of Mathematical Sciences, Fudan University, Shanghai 200433, P. R. China
Abstract:
Let Y be a smooth projective surface defined over an algebraically closed field k with char k ≠ 2, and let τ: X → Y be a double covering branched along a smooth divisor. We show that IX is stable with respect to τ*H if the tangent bundle IY is semi-stable with respect to some ample line bundle H on Y.