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.
and 23 Related for: Lefschetz hyperplane theorem information
specifically in algebraic geometry and algebraic topology, the Lefschetzhyperplanetheorem is a precise statement of certain relations between the shape...
Lefschetz pencil of hyperplane sections is a more subtle system than a Morse function because hyperplanes intersect each other). The Picard–Lefschetz...
collectively as Bertini's theorem. The topology of hyperplane sections is studied in the topic of the Lefschetzhyperplanetheorem and its refinements. Because...
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...
{\displaystyle H^{1,1}(X)} given by the Lefschetz class [ L ] {\displaystyle [L]} . From the Lefschetzhyperplanetheorem and Hodge duality, the rest of the...
inverse Parallelizable manifold Thom's and Bott's proofs of the Lefschetzhyperplanetheorem Atiyah, Michael (2007). "Raoul Harry Bott. 24 September 1923...
\geq 2} (this is because of the Hurewicz homomorphism and the Lefschetzhyperplanetheorem). In this case the local systems R q f ∗ ( Q _ X ) {\displaystyle...
using the definition of the Euler characteristic and using the Lefschetzhyperplanetheorem. If X ⊂ P 3 {\displaystyle X\subset \mathbb {P} ^{3}} is a degree...
analogue of the Riemann hypothesis. It also led to the proof of Lefschetzhyperplanetheorem and the old and new estimates of the classical exponential sums...
building on Hodge theory. The results include the Lefschetzhyperplanetheorem, the hard Lefschetztheorem, and the Hodge-Riemann bilinear relations. Many...
vanishing theoremLefschetzhyperplanetheorem: an ample divisor in a complex projective variety X is topologically similar to X. Hartshorne (1977), Theorem II...
axioms of a Weil theory is the so-called hard Lefschetztheorem (or axiom): Begin with a fixed smooth hyperplane section W = H ∩ X, where X is a given smooth...
René Thom, Frankel and Aldo Andreotti gave a new proof of the Lefschetzhyperplanetheorem using Morse theory. The crux of the argument is the algebraic...
\mathbb {CP} ^{n+m}} are the intersection of hyperplane sections, we can use the Lefschetzhyperplanetheorem to deduce that H j ( X ) = Z {\displaystyle...
has an associated long exact sequence in cohomology. From the Lefschetzhyperplanetheorem there is only one interesting cohomology group of X {\displaystyle...
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...
projective space Plane at infinity, hyperplane at infinity Projective frame Projective transformation Fundamental theorem of projective geometry Duality (projective...
structure on H 3 ( X ) {\displaystyle H^{3}(X)} . Using the Lefschetzhyperplanetheorem the only non-trivial cohomology group is H 3 ( X ) {\displaystyle...
analogues of the Lefschetzhyperplanetheorems. In general such theorems state that homology or cohomology is supported on a hyperplane section of an algebraic...
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...
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)...