The generalized Eckardt point characterization for smooth hypersurfaces

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Let XX be a smooth hypersurface of degree n≥3n\geq 3 in Pn\mathbb{P}^n. A wild tiger for XX is an anticanonical divisor S∈∣−KX∣S\in |-K_X| attaining the total log canonical threshold of XX, and LCS(X,cS)LCS(X,cS) denotes the locus of log canonical singularities of the pair (X,cS)(X,cS). An Eckardt point is a point p∈Xp\in X for which an anticanonical divisor is a cone in Pn−1\mathbb{P}^{n-1} over a smooth hypersurface of degree nn in Pn−2\mathbb{P}^{n-2} with vertex pp.

Generalized Eckardt point conjecture. If the total log canonical threshold of XX is n−1n\frac{n-1}{n}, then a wild tiger SS for XX is a cone in Pn−1\mathbb{P}^{n-1} over a smooth hypersurface of degree nn in Pn−2\mathbb{P}^{n-2} with vertex pp. Moreover,

LCS(X,n−1nS)={p},LCS\left(X,\frac{n-1}{n}S\right)=\{p\},

where pp is an Eckardt point of XX.

This conjectures that attaining the threshold n−1n\frac{n-1}{n} characterizes the generalized Eckardt-point configuration; the preceding discussion establishes the analogous implication for smooth cubic surfaces and the theorem gives the forward construction from an Eckardt point. The general converse is left open.

References

Primary source

Ivan Cheltsov and Jihun Park, “Log Canonical Thresholds and Generalized Eckardt Points”, arXiv:math/0003121 (2001).

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