24 research outputs found
Cohomological descent theory for a morphism of stacks and for equivariant derived categories
In the paper we answer the following question: for a morphism of varieties
(or, more generally, stacks), when the derived category of the base can be
recovered from the derived category of the covering variety by means of descent
theory? As a corollary, we show that for an action of a reductive group on a
scheme, the derived category of equivariant sheaves is equivalent to the
category of objects, equipped with an action of the group, in the ordinary
derived category.Comment: 28 page
Nef divisors for moduli spaces of complexes with compact support
In [BM14b], the first author and Macr\`i constructed a family of nef divisors
on any moduli space of Bridgeland-stable objects on a smooth projective variety
X. In this article, we extend this construction to the setting of any separated
scheme Y of finite type over a field, where we consider moduli spaces of
Bridgeland-stable objects on Y with compact support. We also show that the nef
divisor is compatible with the polarising ample line bundle coming from the GIT
construction of the moduli space in the special case when Y admits a tilting
bundle and the stability condition arises from a \theta-stability condition for
the endomorphism algebra.
Our main tool generalises the work of Abramovich--Polishchuk [AP06] and
Polishchuk [Pol07]: given a t-structure on the derived category D_c(Y) on Y of
objects with compact support and a base scheme S, we construct a constant
family of t-structures on a category of objects on YxS with compact support
relative to S.Comment: 36 pages. In memory of Johan Louis Dupont. V2: updated following
comments from the referee and from Joe Karmazyn who gave a counterexample to
a false claim in version 1. To appear in Selecta Mat