5 papers · 1 filter
Relative and absolute Lefschetz standard conjectures for some Lagrangian fibrations
Giuseppe Ancona, Mattia Cavicchi, Robert Laterveer +1
We show that the hyper-Kähler varieties of OG10-type constructed by Laza-Saccà -Voisin (LSV) verify the Lefschetz standard conjecture. This is an application of a more general res…
Ramified periods and field of definition
Giuseppe Ancona, DragoÅ FrÄÅ£ilÄ, Alberto Vezzani
Let be an extension of number fields that is ramified above . We give a new obstruction to the descent to of smooth projective varieties defined over . The obstruct…
An Artin--Mumford criterion for conic bundles in characteristic two
Emiliano Ambrosi, Giuseppe Ancona
We prove a characteristic two version of the famous criterion of Artin and Mumford for irrationality of conic bundles. On the one hand, combined with the pathological behaviour of…
The Hilbert symbol in the Hodge standard conjecture
Giuseppe Ancona, Adriano Marmora
We study the Hodge standard conjecture for varieties over finite fields admitting a CM lifting, such as abelian varieties or products of K3 surfaces. For those varieties we show th…
Ngô support theorem and polarizability of quasi-projective commutative group schemes
Giuseppe Ancona, Dragos Fratila
We prove that any commutative group scheme over an arbitrary base scheme of finite type over a field with connected fibers and admitting a relatively ample line bundle is polarizab…