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In algebraic topology, the intersection number appears as the Poincaré dual of the cup product. Specifically, if two manifolds, X and Y , intersect transversely in a manifold M , the homology class of the intersection is the Poincaré dual of the cup product D M X ⌣ D M Y {\displaystyle D_{M}X\smile D_{M}Y} of the Poincaré duals of X and Y .
Intuitively, the fixed points are the points of intersection of the graph of f with the diagonal (graph of the identity mapping) in , and the Lefschetz number thereby becomes an intersection number. The Atiyah–Bott theorem is an equation in which the LHS must be the outcome of a global topological (homological) calculation, and the RHS a sum ...
At the other extreme, if A = B is a non-singular subvariety, the self-intersection formula says that A · B is represented by the top Chern class of the normal bundle of A in X. To give a definition, in the general case, of the intersection multiplicity was the major concern of André Weil's 1946 book Foundations of Algebraic Geometry.
In mathematics, and especially differential topology and gauge theory, Donaldson's theorem states that a definite intersection form of a compact, oriented, smooth manifold of dimension 4 is diagonalizable. If the intersection form is positive (negative) definite, it can be diagonalized to the identity matrix (negative identity matrix) over the ...
A three-dimensional model of a figure-eight knot.The figure-eight knot is a prime knot and has an Alexander–Briggs notation of 4 1.. Topology (from the Greek words τόπος, 'place, location', and λόγος, 'study') is the branch of mathematics concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling ...
The topological recursion is a construction in algebraic geometry. [1] It takes as initial data a spectral curve: the data of (,,,,,), where: : is a covering of Riemann surfaces with ramification points; , is a meromorphic differential 1-form on , regular at the ramification points; , is a symmetric meromorphic bilinear differential form on having a double pole on the diagonal and no residue.
encodes all the intersection indices as its coefficients. Witten's conjecture states that the partition function Z = exp F is a τ-function for the KdV hierarchy , in other words it satisfies a certain series of partial differential equations corresponding to the basis { L − 1 , L 0 , L 1 , … } {\displaystyle \{L_{-1},L_{0},L_{1},\ldots ...
By Wu's formula, a spin 4-manifold must have even intersection form, i.e., (,) is even for every x. For a simply-connected smooth 4-manifold (or more generally one with no 2-torsion residing in the first homology), the converse holds. The signature of the intersection form is an important invariant.