Counterexample to Fujita conjecture in positive characteristic
Speaker: Lei Zhang (USTC)

Time: 8h, 5/2/2021

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Abstract: Fujita conjecture was proposed over complex numbers, which predicts that for a smooth projective variety X and an ample line bundle L on X, K_X + (dim X+1)L is base point free and K_X + nL is very ample if n > dim X+1. Joint with Yi Gu, Yongming Zhang, we find counterexamples to this elegant conjecture in positive characteristic. These examples stem from Raynaud’s surfaces. I will first report some related results on this topic and explain the construction and the proof.

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