三次曲面第二类轨迹的万有覆叠
The universal cover of the second-type locus of a cubic
AI总结：
该数学研究证明一般四次三维空间中第二类直线构成的曲面基本群阶为2，Huybrechts利用第二类直线上高斯映射的两个分歧点构造了其万有覆叠。
AI中文摘要：
我们证明，一般四次三维空间中第二类直线构成的曲面的基本群阶为2。Huybrechts构造的其万有覆叠，是通过考虑每条第二类直线上高斯映射的两个分歧点得到的。
英文摘要：
We prove that the surface of second-type lines on a general cubic fourfold has fundamental group of order two. Its universal cover, constructed by Huybrechts, is obtained by considering the two ramification points of the Gauss map along each second-type line.
