Fix a smooth complex
projective n-fold X, n ≥ 5, with H1(X,𝒪X) = 0. Then there is a smooth projective
n-fold Y birational to X and H ∈ Pic(Y ), H ample, with the following property. For
any d ∈ Z let M(Y,2,𝒪,d,H) be the moduli scheme of H-stable rank 2 vector
bundles, E, on Y with det(E)≅𝒪Y and c2(E) ⋅ Hn−2 = d. Let m(Y,2,𝒪,d,H) be
the number of its irreducible components. Then limsupd→∞m(Y,2,𝒪,d,
H) = +∞.
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