Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-03T01:25:36.182Z Has data issue: false hasContentIssue false

Symmetry and parity in Frobenius action on cohomology

Published online by Cambridge University Press:  08 December 2011

Junecue Suh*
Affiliation:
Department of Mathematics, FAS Harvard University, One Oxford Street, Cambridge, MA 02138, USA (email: [email protected])
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We prove that the Newton polygons of Frobenius on the crystalline cohomology of proper smooth varieties satisfy a symmetry that results, in the case of projective smooth varieties, from Poincaré duality and the hard Lefschetz theorem. As a corollary, we deduce that the Betti numbers in odd degrees of any proper smooth variety over a field are even (a consequence of Hodge symmetry in characteristic zero), answering an old question of Serre. Then we give a generalization and a refinement for arbitrary varieties over finite fields, in response to later questions of Serre and of Katz.

Type
Research Article
Copyright
Copyright © Foundation Compositio Mathematica 2011

References

[SGA4]Artin, M., Grothendieck, A. and Verdier, J. L. (eds), Théorie des topos et cohomologie étale des schemas: Séminaire de Géométrie Algébrique du Bois-Marie 1963/1964 SGA 4, Lecture Notes in Mathematics, vol. 305 (Springer, 1973).Google Scholar
[Ber74]Berthelot, P., Cohomologie cristalline des schémas de caractéristique p>0, Lecture Notes in Mathematics, vol. 407 (Springer, 1974).Google Scholar
[Ber97]Berthelot, P., Finitude et pureté cohomologique en cohomologie rigide, Invent. Math. 128 (1997), 329377, with an appendix by A. J. de Jong.CrossRefGoogle Scholar
[Chi98]Chiarellotto, B., Weights in rigid cohomology. Applications to unipotent F-isocrystals, Ann. Sci. Éc. Norm. Supér. (4) 31 (1998), 683715.CrossRefGoogle Scholar
[CL98]Chiarellotto, B. and Le Stum, B., Sur la pureté de la cohomologie cristalline, C. R. Acad. Sci. Paris Sér. I Math. 326 (1998), 961963.CrossRefGoogle Scholar
[CT03]Chiarellotto, B. and Tsuzuki, N., Cohomological descent of rigid cohomology for étale coverings, Rend. Semin. Mat. Univ. Padova 109 (2003), 63215.Google Scholar
[deJ96]de Jong, A. J., Smoothness, semi-stability and alterations, Publ. Math. Inst. Hautes Études Sci. 83 (1996), 5193.CrossRefGoogle Scholar
[deJ97]de Jong, A. J., Families of curves and alterations, Ann. Inst. Fourier (Grenoble) 47 (1997), 599621.CrossRefGoogle Scholar
[Del68]Deligne, P., Théorème de Lefschetz et critères de dégénérescence de suites spectrales, Publ. Math. Inst. Hautes Études Sci. 35 (1968), 259278.CrossRefGoogle Scholar
[Del74]Deligne, P., La conjecture de Weil. I, Publ. Math. Inst. Hautes Études Sci. 43 (1974), 273307.CrossRefGoogle Scholar
[SGA41/2]Deligne, P., Cohomologie étale: Séminaire de Géométrie Algébrique du Bois-Marie SGA 4 1/2, Lecture Notes in Mathematics, vol. 569 (Springer, 1977).CrossRefGoogle Scholar
[Del80]Deligne, P., La conjecture de Weil. II, Publ. Math. Inst. Hautes Études Sci. 52 (1980), 137252.CrossRefGoogle Scholar
[EGA2]Grothendieck, A., Eléments de géométrie algébrique, II: Étude globale élémentaire de quelques classes de morphismes, Publ. Math. Inst. Hautes Études Sci. 8 (1961).Google Scholar
[EGA4]Grothendieck, A., Éléments de géometrié algébrique, IV: Étude locale des schémás et des morphismes de schémas I–IV, Publ. Math. Inst. Hautes Études Sci. 20, 24, 28, 32 (1964–67).Google Scholar
[ÉL93]Étesse, J.-Y. and Le Stum, B., Fonctions L associées aux F-isocristaux surconvergents. I. Interprétation cohomologique, Math. Ann. 296 (1993), 557576.CrossRefGoogle Scholar
[Gab83]Gabber, O., Sur la torsion dans la cohomologie -adique d’une variété, C. R. Acad. Sci. Paris Sér. I Math. 297 (1983), 179182.Google Scholar
[GM87]Gillet, H. and Messing, W., Cycle classes and Riemann–Roch for crystalline cohomology, Duke Math. J. 55 (1987), 501538.CrossRefGoogle Scholar
[Ill06]Illusie, L., Miscellany on traces in -adic cohomology: a survey, Jpn. J. Math. 1 (2006), 107136.CrossRefGoogle Scholar
[Kat79]Katz, N., Slope filtration of F-crystals, in Journées de Géométrie Algébrique de Rennes (Rennes, 1978), Vol. I, Astérisque, vol. 63 (Société Mathématique de France, Paris, 1979), 113163.Google Scholar
[KM74]Katz, N. and Messing, W., Some consequences of the Riemann hypothesis for varieties over finite fields, Invent. Math. 23 (1974), 7377.CrossRefGoogle Scholar
[Tsu03]Tsuzuki, N., Cohomological descent of rigid cohomology for proper coverings, Invent. Math. 151 (2003), 101133.CrossRefGoogle Scholar