Standard conjecture for nearby and vanishing cohomology

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Let X→SX\to S be the projective family in the paper, let XsX_s be its special fiber, let XηX_\eta be its generic fiber, and let Hψ∗(Xs)H^*_{\psi}(X_s) and Hϕ∗(Xs)H^*_{\phi}(X_s) denote the nearby- and vanishing-cycle cohomology groups. Fix an ample line bundle LL on XX, and let L{\mathsf L} be cup product with c1(L)∈H2(Xs)(1)c_1(L)\in H^2(X_s)(1). Set n=dim⁡Xηn=\dim X_\eta. Standard conjecture for nearby and vanishing cohomology. For i≤ni\leq n, there is an isomorphism

Li:Hψn−i(Xs)⟶∼Hψn+i(Xs)(i),{\mathsf L}^i:H^{n-i}_{\psi}(X_s)\overset{\sim}{\longrightarrow}H^{n+i}_{\psi}(X_s)(i),

and for i≤n+1i\leq n+1, there is an isomorphism

Li:Hϕn+1−i(Xs)⟶∼Hϕn+1+i(Xs)(i).{\mathsf L}^i:H^{n+1-i}_{\phi}(X_s)\overset{\sim}{\longrightarrow}H^{n+1+i}_{\phi}(X_s)(i).

This is proposed as an analogue of Grothendieck's standard conjectures for nearby and vanishing cohomology; the supplied text gives no resolution status.

References

Primary source

Shou-Wu Zhang, “Standard Conjectures and Height Pairings”, arXiv:2009.07089 (2022).

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