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Lefschetz hyperplane theorem information


In mathematics, specifically in algebraic geometry and algebraic topology, the Lefschetz hyperplane theorem is a precise statement of certain relations between the shape of an algebraic variety and the shape of its subvarieties. More precisely, the theorem says that for a variety X embedded in projective space and a hyperplane section Y, the homology, cohomology, and homotopy groups of X determine those of Y. A result of this kind was first stated by Solomon Lefschetz for homology groups of complex algebraic varieties. Similar results have since been found for homotopy groups, in positive characteristic, and in other homology and cohomology theories.

A far-reaching generalization of the hard Lefschetz theorem is given by the decomposition theorem.

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Lefschetz hyperplane theorem

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specifically in algebraic geometry and algebraic topology, the Lefschetz hyperplane theorem is a precise statement of certain relations between the shape...

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Solomon Lefschetz

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Lefschetz pencil of hyperplane sections is a more subtle system than a Morse function because hyperplanes intersect each other). The Picard–Lefschetz...

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Hyperplane section

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collectively as Bertini's theorem. The topology of hyperplane sections is studied in the topic of the Lefschetz hyperplane theorem and its refinements. Because...

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List of theorems

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theorem (topology) Lefschetz hyperplane theorem (algebraic topology) Lefschetz theorem on (1,1)-classes (algebraic geometry) Lehmann–Scheffé theorem (statistics)...

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Hodge index theorem

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non-singular projective surface, and let H be the divisor class on V of a hyperplane section of V in a given projective embedding. Then the intersection H...

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Hodge structure

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{\displaystyle H^{1,1}(X)} given by the Lefschetz class [ L ] {\displaystyle [L]} . From the Lefschetz hyperplane theorem and Hodge duality, the rest of the...

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Raoul Bott

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inverse Parallelizable manifold Thom's and Bott's proofs of the Lefschetz hyperplane theorem Atiyah, Michael (2007). "Raoul Harry Bott. 24 September 1923...

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Leray spectral sequence

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\geq 2} (this is because of the Hurewicz homomorphism and the Lefschetz hyperplane theorem). In this case the local systems R q f ∗ ( Q _ X ) {\displaystyle...

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Chern class

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using the definition of the Euler characteristic and using the Lefschetz hyperplane theorem. If X ⊂ P 3 {\displaystyle X\subset \mathbb {P} ^{3}} is a degree...

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Pierre Deligne

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analogue of the Riemann hypothesis. It also led to the proof of Lefschetz hyperplane theorem and the old and new estimates of the classical exponential sums...

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Projective variety

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projective spaces Adequate equivalence relation Hilbert scheme Lefschetz hyperplane theorem Minimal model program Kollár & Moduli, Ch I. Shafarevich, Igor...

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Hodge theory

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building on Hodge theory. The results include the Lefschetz hyperplane theorem, the hard Lefschetz theorem, and the Hodge-Riemann bilinear relations. Many...

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Ample line bundle

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vanishing theorem Lefschetz hyperplane theorem: an ample divisor in a complex projective variety X is topologically similar to X. Hartshorne (1977), Theorem II...

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Standard conjectures on algebraic cycles

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axioms of a Weil theory is the so-called hard Lefschetz theorem (or axiom): Begin with a fixed smooth hyperplane section W = H ∩ X, where X is a given smooth...

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Theodore Frankel

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René Thom, Frankel and Aldo Andreotti gave a new proof of the Lefschetz hyperplane theorem using Morse theory. The crux of the argument is the algebraic...

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Complete intersection

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\mathbb {CP} ^{n+m}} are the intersection of hyperplane sections, we can use the Lefschetz hyperplane theorem to deduce that H j ( X ) = Z {\displaystyle...

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Jacobian ideal

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has an associated long exact sequence in cohomology. From the Lefschetz hyperplane theorem there is only one interesting cohomology group of X {\displaystyle...

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Glossary of algebraic topology

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space of formal group laws. Lefschetz 1.  Solomon Lefschetz 2.  The Lefschetz fixed-point theorem says: given a finite simplicial complex K and its geometric...

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List of algebraic geometry topics

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projective space Plane at infinity, hyperplane at infinity Projective frame Projective transformation Fundamental theorem of projective geometry Duality (projective...

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Mirror symmetry conjecture

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structure on H 3 ( X ) {\displaystyle H^{3}(X)} . Using the Lefschetz hyperplane theorem the only non-trivial cohomology group is H 3 ( X ) {\displaystyle...

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Local cohomology

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analogues of the Lefschetz hyperplane theorems. In general such theorems state that homology or cohomology is supported on a hyperplane section of an algebraic...

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Glossary of arithmetic and diophantine geometry

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equal. Subspace theorem Schmidt's subspace theorem shows that points of small height in projective space lie in a finite number of hyperplanes. A quantitative...

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Weil cohomology theory

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be the inclusion Z ⊂ K. Weak Lefschetz axiom: For any smooth hyperplane section j: W ⊂ X (i.e. W = X ∩ H, H some hyperplane in the ambient projective space)...

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