扭曲旗上异常集合的不存在性和通过非交换动机的范畴可表示性
Non-existence of exceptional collections on twisted flags and categorical representability via noncommutative motives
摘要：
本文证明了Brauer-Severi簇的有限积是零维范畴表示的当且仅当它有一个$k$ -有理点当且仅当它是$k$上的有理点.对于特征不同于2的域$k$上的某些迷向对合簇也是如此。对于广义Brauer-Severi簇的有限积，零维范畴表示等价于存在一个完全例外集。然而，在这种情况下，零维范畴的可表示性并不等同于存在一个有理点。我们还表明，非平凡的扭曲标志的经典类型$A_n$和$C_n$不能有完整的异常集合，以这种方式扩大了以前已知的例子。最后，我们确定的范畴表示维数$\mathrm{rdim}(X)$的广义Brauer-Severi品种的指数$\leq 3$和某些扭曲形式的光滑二次曲面（对合品种）。
英文摘要：
In this paper we prove that a finite product of Brauer--Severi varieties is categorical representable in dimension zero if and only if it admits a $k$-rational point if and only if it is rational over $k$. The same is true for certain isotropic involution varieties over a field $k$ of characteristic different from two. For finite products of generalized Brauer--Severi varieties, categorical representability in dimension zero is equivalent to the existence of a full exceptional collection. In this case however categorical representability in dimension zero is not equivalent to the existence of a rational point. We also show that non-trivial twisted flags of classical type $A_n$ and $C_n$ cannot have full exceptional collections, enlarging in this way the set of previous known examples. Finally, we determine the categorical representability dimension $\mathrm{rdim}(X)$ for generalized Brauer--Severi varieties of index $\leq 3$ and for certain twisted forms of smooth quadrics (involution varieties).
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