SMS scnews item created by Leo Tzou at Mon 8 May 2017 1806
Type: Seminar
Distribution: World
Expiry: 7 Nov 2017
Calendar1: 26 May 2017 1400-1500
CalLoc1: UNSW Red Centre 4082
CalTitle1: Derived equivalence and Grothendieck ring of varieties
Auth: leo@dyn-129-78-250-131.wirelessguest.usyd.edu.au (ltzo2369) in SMS-WASM

# Joint Colloquium: Okawa -- Derived equivalence and Grothendieck ring of varieties

Bounded derived category of coherent sheaves of an algebraic variety is a relatively new
but very important invariant.  There are examples of non-singular projective varieties
XX and YY which have the equivalent derived category but are even not birational to each
other (meaning, their geometric relationship is not so obvious).  Though it is expected
that derived equivalent XX and YY should share some invariants, we have only partial
knowledge in this direction.  On the other hand, the Grothendieck ring of varieties is
defined as the free abelian group generated by the set of isomorphism classes of
algebraic varieties (over a fixed field kk) modulo the relations
[X]=[Z]+[Xâˆ’Z][X]=[Z]+[Xâˆ’Z], where ZZ is a closed subscheme of XX.  It is a
commutative ring with the product [X][Y]=[XÃ—Y][X][Y]=[XÃ—Y].  Some of the important
invariants of a variety can be recovered from its class in the Grothendieck ring, such
as the number of rational points (when kk is a finite field), topological Euler number
(when k=Ck=C), and the Hodge numbers (again when k=Ck=C).  In this talk I would like to
discuss a question, with a couple of examples, which asks if a pair of derived
equivalent algebraic varieties share the same class in "some" modification of the
Grothendieck ring of varieties.


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