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arxiv: math/0603090 · v1 · submitted 2006-03-03 · 🧮 math.AG

On the Picard number of almost Fano threefolds with pseudo-index >1

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keywords fanoalmostnumberpicardthreefoldsboundarycanonicalcase
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We study Gorenstein almost Fano threefolds X with canonical singularities and pseudoindex > 1. We show that the maximal Picard number of X is 10 in general, 3 if X is Fano, and 8 if X is toric. Moreover, we characterize the boundary cases. In the Fano case, we prove that the generalized Mukai conjecture holds.

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