Relative singular support and the semi-continuity of characteristic cycles for étale sheaves

平展层的导子除子的半连续性

Semi-continuity for conductor divisors of étale sheaves

本文在几何情形下证明了高相对维数平展层的导子除子和对数导子除子的半连续性性质，推广了相对曲线平展层导子的半连续性结果，是André相关结果的高维ℓ-进类比。

On continuity of local epsilon factors of $\ell$-adic sheaves

Let $S$ be a noetherian scheme and $f\colon X\to S$ be a smooth morphism of relative dimension 1. For a locally constant sheaf on the complement of a divisor in $X$ at over $S$, Deligne and Laumon proved that the universal local acyclicity is equivalent to the local constancy of Swan conductors. In this article, assuming the universal local acyclicity, we show an analogous result of the continuity of local epsilon factors. We also give a generalization of this result to a family of isolated singularities.

Semi-continuity for total dimension divisors of étale sheaves

In this article, we extend a pull-back inequality for total dimension divisors of étale sheavs due to Saito. Using this formula, we generalize Deligne and Laumon's lower semi-continuous property for Swan conductors of étale sheaves on relative curves to higher relative dimensions in a geometric situation.

Semi-continuity of Stability for Sheaves and Variation of Gieseker Moduli Spaces

We investigate a semi-continuity property for stability conditions for sheaves that is important for the problem of variation of the moduli spaces as the stability condition changes. We place this in the context of a notion of stability previously considered by the authors, called multi-Gieseker-stability, that generalises the classical notion of Gieseker-stability to allow for several polarisations. As such we are able to prove that on smooth threefolds certain moduli spaces of Gieseker-stable sheaves are related by a finite number of Thaddeus-flips (that is flips arising for Variation of Geo…

Logarithmic ramifications of étale sheaves by restricting to curves

In this article, we prove that the Swan conductor of an étale sheaf on a smooth variety defined by Abbes and Saito's logarithmic ramification theory can be computed by its classical Swan conductors after restricting it to curves. It extends the same result for rank 1 sheaves due to Barrientos. As an application, we give a logarithmic ramification version of generalizations of Deligne and Laumon's lower semi-continuity property for Swan conductors of étale sheaves on relative curves to higher relative dimensions in a geometric situation.

Semi-continuity of conductors, and ramification bound of nearby cycles

For a constructible étale sheaf on a smooth variety of positive characteristic ramified along an effective divisor, the largest slope in Abbes and Saito's ramification theory of the sheaf gives a divisor with rational coefficients called the conductor divisor. In this article, we prove decreasing properties of the conductor divisor after pull-backs. The main ingredient behind is the construction of étale sheaves with pure ramifications. As applications, we first prove a lower semi-continuity property for conductors of étale sheaves on relative curves in the equal characteristic case, which sup…