题目：On the semisimplicity of geometric monodromy action in F_l-coefficients

报告人: 许俊彦博士（清华大学丘成桐数学中心）

Abstract: Let X be a smooth separated geometrically connected variety defined over a characteristic p finite field, f:Y->X a smooth projective morphism, and w a non-negative integer. A celebrated result of Deligne states that the higher direct image Q_l-sheaf R^w f_* Q_l is semisimple on X geometrically for all prime l not equal to p. By comparing the invariant dimensions of sufficiently many l-adic and mod l representations arising from the sheaves R^w f_* Q_l and R^w f_* F_l respectively, we prove that the F_l-sheaf R^w f_* F_l is likewise semisimple on X geometrically if l is sufficiently large. As an application, a largeness result on the monodromy is obtained. This is a joint work with Anna Cadoret and Akio Tamagawa.

时间：11月2日（周五）下午2:00—3:00

地点：首都师大新教2楼 513教室

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