Comparison of fundamental group schemes of a projective variety and an ample hypersurface
Authors:
Indranil Biswas and Yogish I. Holla
Journal:
J. Algebraic Geom. 16 (2007), 547-597
DOI:
https://doi.org/10.1090/S1056-3911-07-00449-3
Published electronically:
March 20, 2007
MathSciNet review:
2306280
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References |
Additional Information
Abstract: Let $X$ be a smooth projective variety defined over an algebraically closed field, and let $L$ be an ample line bundle over $X$. We prove that for any smooth hypersurface $D$ on $X$ in the complete linear system $\vert L^{\otimes d}\vert$, the inclusion map $D\hookrightarrow X$ induces an isomorphism of fundamental group schemes, provided $d$ is sufficiently large and $\dim X \geq 3$. If $\dim X = 2$, and $d$ is sufficiently large, then the induced homomorphism of fundamental group schemes remains surjective. We give an example to show that the homomorphism of fundamental group schemes induced by the inclusion map of a reduced ample curve in a smooth projective surface is not surjective in general.
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[At]At M. F. Atiyah: Complex analytic connections in fibre bundles, Trans. Amer. Math. Soc. 85 (1957), 181–207.
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[Gr]Gr A. Grothendieck: Cohomologie locale des faisceaux cohérents et théorèmes de Lefschetz locaux et globaux (SGA 2), Advanced Studies in Pure Mathematics, Vol. 2. North-Holland Publishing Co., Amsterdam; Masson & Cie, Éditeur, Paris, 1968.
[Ha]Ha R. Hartshorne: Ample subvarieties of algebraic varieties, Lecture Notes in Mathematics, Vol. 156 Springer-Verlag, Berlin-New York, 1970.
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[RR]RR S. Ramanan and A. Ramanathan: Some remarks on the instability flag, Tôhoku Math. Jour. 36 (1984), 269–291.
Additional Information
Indranil Biswas
Affiliation:
School of Mathematics, Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400005, India
MR Author ID:
340073
Email:
indranil@math.tifr.res.in
Yogish I. Holla
Affiliation:
School of Mathematics, Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400005, India
Email:
yogi@math.tifr.res.in
Received by editor(s):
February 16, 2006
Received by editor(s) in revised form:
February 20, 2006
Published electronically:
March 20, 2007