Families of rationally simply connected varieties over surfaces and torsors for semisimple groups
Publications Mathématiques de l'IHÉS, Volume 114 (2011), pp. 1-85

Under suitable hypotheses, we prove that a form of a projective homogeneous variety G/P defined over the function field of a surface over an algebraically closed field has a rational point. The method uses an algebro-geometric analogue of simple connectedness replacing the unit interval by the projective line. As a consequence, we complete the proof of Serre’s Conjecture II in Galois cohomology for function fields over an algebraically closed field.

Received:
Accepted:
Online First:
Published online:
DOI: 10.1007/s10240-011-0035-1

A. J. Jong 1; Xuhua He 2; Jason Michael Starr 3

1 Department of Mathematics, Columbia University New York, NY, 10027 USA
2 Department of Mathematics, The Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong
3 Department of Mathematics, Stony Brook University Stony Brook, NY, 11794 USA
@article{PMIHES_2011__114__1_0,
     author = {A. J. Jong and Xuhua He and Jason Michael Starr},
     title = {Families of rationally simply connected varieties over surfaces and torsors for semisimple groups},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {1--85},
     year = {2011},
     publisher = {Springer-Verlag},
     volume = {114},
     doi = {10.1007/s10240-011-0035-1},
     zbl = {1285.14053},
     language = {en},
     url = {https://pmihes.centre-mersenne.org/articles/10.1007/s10240-011-0035-1/}
}
TY  - JOUR
AU  - A. J. Jong
AU  - Xuhua He
AU  - Jason Michael Starr
TI  - Families of rationally simply connected varieties over surfaces and torsors for semisimple groups
JO  - Publications Mathématiques de l'IHÉS
PY  - 2011
SP  - 1
EP  - 85
VL  - 114
PB  - Springer-Verlag
UR  - https://pmihes.centre-mersenne.org/articles/10.1007/s10240-011-0035-1/
DO  - 10.1007/s10240-011-0035-1
LA  - en
ID  - PMIHES_2011__114__1_0
ER  - 
%0 Journal Article
%A A. J. Jong
%A Xuhua He
%A Jason Michael Starr
%T Families of rationally simply connected varieties over surfaces and torsors for semisimple groups
%J Publications Mathématiques de l'IHÉS
%D 2011
%P 1-85
%V 114
%I Springer-Verlag
%U https://pmihes.centre-mersenne.org/articles/10.1007/s10240-011-0035-1/
%R 10.1007/s10240-011-0035-1
%G en
%F PMIHES_2011__114__1_0
A. J. Jong; Xuhua He; Jason Michael Starr. Families of rationally simply connected varieties over surfaces and torsors for semisimple groups. Publications Mathématiques de l'IHÉS, Volume 114 (2011), pp. 1-85. doi: 10.1007/s10240-011-0035-1

[AV02] D. Abramovich; A. Vistoli Compactifying the space of stable maps, J. Am. Math. Soc., Volume 15 (2002), pp. 27-75 (electronic) | MR | Zbl | DOI

[BGI71] Théorie des intersections et théorème de Riemann-Roch (P. Berthelot; A. Grothendieck; L. Illusie, eds.), Springer, Berlin, 1971 Séminaire de Géométrie Algébrique du Bois-Marie 1966–1967 (SGA 6), Dirigé par P. Berthelot, A. Grothendieck et L. Illusie. Avec la collaboration de D. Ferrand, J. P. Jouanolou, O. Jussila, S. Kleiman, M. Raynaud et J. P. Serre, Lecture Notes in Mathematics, Vol. 225 | Zbl

[BLR90] S. Bosch; W. Lütkebohmert; M. Raynaud Néron Models, Ergebnisse der Mathematik und ihrer Grenzgebiete (3) [Results in Mathematics and Related Areas (3)], 21, Springer, Berlin, 1990 | Zbl

[BM96] K. Behrend; Yu. Manin Stacks of stable maps and Gromov-Witten invariants, Duke Math. J., Volume 85 (1996), pp. 1-60 | MR | Zbl | DOI

[Bor91] A. Borel Linear Algebraic Groups, Springer, Berlin, 1991 | Zbl | DOI

[CC98] A. M. Cohen; B. N. Cooperstein Lie incidence systems from projective varieties, Proc. Am. Math. Soc., Volume 126 (1998), pp. 2095-2102 | MR | Zbl | DOI

[Che95] C. Chevalley Certains schémas de groupes semi-simples, Séminaire Bourbaki (6), Soc. Math. France, Paris (1995), pp. 219-234

[Coh95] A. M. Cohen Point-line spaces related to buildings, Handbook of Incidence Geometry, North-Holland, Amsterdam (1995), pp. 647-737 | Zbl | DOI

[CTGP04] J.-L. Colliot-Thélène; P. Gille; R. Parimala Arithmetic of linear algebraic groups over 2-dimensional geometric fields, Duke Math. J., Volume 121 (2004), pp. 285-341 | MR | Zbl | DOI

[Dem65] M. Demazure Schémas en groupes réductifs, Bull. Soc. Math. Fr., Volume 93 (1965), pp. 369-413 | MR | Zbl | Numdam

[Dem77] M. Demazure Automorphismes et déformations des variétés de Borel, Invent. Math., Volume 39 (1977), pp. 179-186 | MR | Zbl | DOI

[dJS05a] A. J. de Jong and J. Starr, Almost proper git-stacks and discriminant avoidance. preprint, available http://www.math.columbia.edu/~dejong/, 2005. | Zbl

[dJS05b] A. J. de Jong and J. Starr, A remark on isotrivial families. preprint, available http://www.math.columbia.edu/~dejong/, 2005.

[dJS06] A. J. de Jong and J. Starr, Low degree complete intersections are rationally simply connected. In preparation, 2006.

[Elk73] R. Elkik Solutions d’équations à coefficients dans un anneau hensélien, Ann. Sci. École Norm. Sup., Volume 6 (1974), pp. 553-603 | MR | Zbl | Numdam

[Fal03] G. Faltings Finiteness of coherent cohomology for proper fppf stacks, J. Algebr. Geom., Volume 12 (2003), pp. 357-366 | MR | Zbl | DOI

[FP97] W. Fulton; R. Pandharipande Notes on stable maps and quantum cohomology, Algebraic geometry—Santa Cruz 1995 (Proc. Sympos. Pure Math., 62), Amer. Math. Soc., Providence (1997), pp. 45-96 | Zbl

[GHMS05] T. Graber; J. Harris; B. Mazur; J. Starr Rational connectivity and sections of families over curves, Ann. Sci. École Norm. Sup. (4), Volume 38 (2005), pp. 671-692 | MR | Zbl | Numdam

[GHS03] T. Graber; J. Harris; J. Starr Families of rationally connected varieties, J. Am. Math. Soc., Volume 16 (2003), pp. 57-67 (electronic) | MR | Zbl | DOI

[Gro62] A. Grothendieck Fondements de la Géométrie Algébrique. [Extraits du Séminaire Bourbaki, 1957–1962.], Secrétariat mathématique, Paris, 1962 | Zbl

[Gro63] A. Grothendieck Éléments de géométrie algébrique. III. Étude locale des schémas et des morphismes de schémas, Inst. Hautes Études Sci. Publ. Math., Volume 17 (1963), pp. 137-223 (http://www.numdam.org/item?id=PMIHES_1961__11__5_0) | Zbl | Numdam

[Gro67] A. Grothendieck Éléments de géométrie algébrique. IV. Étude locale des schémas et des morphismes de schémas, Inst. Hautes Études Sci. Publ. Math., Volume 32 (1967), pp. 5-361 (http://www.numdam.org/item?id=PMIHES_1965__24__5_0) | DOI | Zbl | Numdam

[Har71] G. Harder Semisimple group schemes over curves and automorphic functions, Actes du Congrès International des Mathématiciens (Nice, 1970), Tome 2, Gauthier-Villars, Paris (1971), pp. 307-312 | Zbl

[Har75] G. Harder Über die Galoiskohomologie halbeinfacher algebraischer Gruppen. III, J. Reine Angew. Math., Volume 274/275 (1975), pp. 125-138 (Collection of articles dedicated to Helmut Hasse on his seventy-fifth birthday, III) | MR | Zbl | DOI

[Har77] R. Hartshorne Algebraic geometry, Springer, New York, 1977 (Graduate Texts in Mathematics, No. 52) | Zbl

[Hir64] H. Hironaka Resolution of singularities of an algebraic variety over a field of characteristic zero. I, II, Ann. of Math., Volume 79 (1964), pp. 109-203 | MR | Zbl | DOI

[Hir64a] H. Hironaka Resolution of singularities of an algebraic variety over a field of characteristic zero. I, II, Ann. of Math., Volume 79 (1964), pp. 205-326 | MR | Zbl | DOI

[HS05] J. Harris; J. Starr Rational curves on hypersurfaces of low degree. II, Compos. Math., Volume 141 (2005), pp. 35-92 | MR | Zbl | DOI

[HT06] B. Hassett; Y. Tschinkel Weak approximation over function fields, Invent. Math., Volume 163 (2006), pp. 171-190 | MR | Zbl | DOI

[Ill71] L. Illusie Complexe cotangent et déformations. I, Lecture Notes in Mathematics, 239, Springer, Berlin, 1971 | Zbl

[Kem76] G. R. Kempf Linear systems on homogeneous spaces, Ann. of Math. (2), Volume 103 (1976), pp. 557-591 | MR | Zbl | DOI

[Kle66] S. L. Kleiman Toward a numerical criterion of ampleness, Ann. of Math. (2), Volume 84 (1966), pp. 293-344 | MR | Zbl | DOI

[KM76] F. F. Knudsen; D. Mumford The projectivity of the moduli space of stable curves. I. Preliminaries on “det” and “Div”, Math. Scand., Volume 39 (1976), pp. 19-55 | MR | Zbl

[KM97] S. Keel; S. Mori Quotients by groupoids, Ann. of Math. (2), Volume 145 (1997), pp. 193-213 | MR | Zbl | DOI

[KMM92a] J. Kollár; Y. Miyaoka; S. Mori Rational connectedness and boundedness of Fano manifolds, J. Differ. Geom., Volume 36 (1992), pp. 765-779 | Zbl

[KMM92b] J. Kollár; Y. Miyaoka; S. Mori Rationally connected varieties, J. Algebr. Geom., Volume 1 (1992), pp. 429-448 | Zbl

[Kol96] J. Kollár Rational curves on algebraic varieties, Ergebnisse der Mathematik und ihrer Grenzgebiete. 3. Folge. A Series of Modern Surveys in Mathematics [Results in Mathematics and Related Areas. 3rd Series. A Series of Modern Surveys in Mathematics], 32, Springer, Berlin, 1996 | Zbl

[Kon95] M. Kontsevich Enumeration of rational curves via torus actions, The Moduli Space of Curves (Progr. Math., 129), Birkhäuser, Boston (1995), pp. 335-368 | Zbl | DOI

[Lan52] S. Lang On quasi algebraic closure, Ann. of Math. (2), Volume 55 (1952), pp. 373-390 | MR | Zbl | DOI

[Lie06] M. Lieblich Remarks on the stack of coherent algebras, Int. Math. Res. Not., Volume 12 (2006), p. 75273 | MR | Zbl

[LMB00] G. Laumon; L. Moret-Bailly Champs algébriques, Ergebnisse der Mathematik und ihrer Grenzgebiete. 3. Folge. A Series of Modern Surveys in Mathematics [Results in Mathematics and Related Areas. 3rd Series. A Series of Modern Surveys in Mathematics], 39, Springer, Berlin, 2000 | Zbl

[Mat80] H. Matsumura Commutative algebra, Mathematics Lecture Note Series, 56, Benjamin/Cummings, Reading, 1980 | Zbl

[Mil80] J. S. Milne Étale cohomology, Princeton Mathematical Series, 33, Princeton University Press, Princeton, 1980 | Zbl

[MR04] R. J. Marsh; K. Rietsch Parametrizations of flag varieties, Represent. Theory, Volume 8 (2004), pp. 212-242 | MR | Zbl | DOI

[Mum70] D. Mumford Abelian varieties, Tata Institute of Fundamental Research Studies in Mathematics, 5, Published for the Tata Institute of Fundamental Research, Bombay, 1970 | Zbl

[Ols05] M. C. Olsson On proper coverings of Artin stacks, Adv. Math., Volume 198 (2005), pp. 93-106 | MR | Zbl | DOI

[Ols06] M. C. Olsson Hom-stacks and restriction of scalars, Duke Math. J., Volume 134 (2006), pp. 139-164 | MR | Zbl | DOI

[Pop74] V. L. Popov Picard groups of homogeneous spaces of linear algebraic groups and one-dimensional homogeneous vector fiberings, Izv. Akad. Nauk SSSR, Ser. Mat., Volume 38 (1974), pp. 294-322 | MR | Zbl

[Slo80] P. Slodowy Simple singularities and simple algebraic groups, Lecture Notes in Mathematics, 815, Springer, Berlin, 1980 | Zbl

[Spr98] T. A. Springer Linear algebraic groups, Progress in Mathematics, 9, Birkhäuser, Boston, 1998 | Zbl | DOI

[Sta04] J. Starr, Hypersurfaces of low degree are rationally simply-connected. Preprint, 2004.

[Sta06] J. Starr, Artin’s axioms, composition and moduli spaces. Preprint, 2006.

Cited by Sources: