Whitehead product in homotopy theory

E886920

The Whitehead product in homotopy theory is a bilinear operation on homotopy groups that captures how spheres can be nontrivially linked or composed within a topological space.

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Surface form Occurrences
Whitehead product 0

Statements (48)

Predicate Object
instanceOf algebraic operation
bilinear operation on homotopy groups
construction in homotopy theory
actsOn homotopy groups
π_m(X)
π_n(X)
appearsIn homotopy spectral sequences
long exact sequences of homotopy groups for pairs
arity binary operation
captures interaction of homotopy classes of maps from spheres
linking behavior of spheres in a space
nontrivial compositions of sphere maps
codomain π_{n+m-1}(X)
constructionUses attaching map from S^{m+n-1} to S^m ∨ S^n
commutator-like map on spheres
wedge sum S^m ∨ S^n
context graded homotopy groups π_*(X)
definedIn homotopy category of pointed spaces
domainCondition α ∈ π_m(X), β ∈ π_n(X)
field algebraic topology
firstIntroducedBy J. H. C. Whitehead NERFINISHED
generalizes commutator in fundamental groups
gives higher order operations in homotopy
isDefinedFor pointed topological spaces
isToolFor detecting nontrivial elements in homotopy groups
studying attaching maps of cells in CW-complexes
isZeroFor simply connected suspensions under suitable conditions
namedAfter J. H. C. Whitehead NERFINISHED
nontrivialExample Hopf invariant phenomena in homotopy groups of spheres
[ι_n,ι_n] in π_{2n-1}(S^n) for n>1
outputCondition [α,β] ∈ π_{m+n-1}(X)
property bilinear
functorial
graded skew-commutative
natural with respect to continuous maps
relatedTo Lie algebra structure on homotopy groups of an H-space
Samelson product NERFINISHED
requires chosen basepoint
satisfies [α,β] = −(−1)^{mn}[β,α] for α∈π_m, β∈π_n
graded Jacobi identity up to sign
structureType graded Lie algebra up to homotopy
usedIn Postnikov tower computations
description of k-invariants
homotopy Lie algebra of a space
obstruction theory
study of homotopy groups of spheres
vanishesOn H-spaces under suitable conditions
yearIntroducedApprox mid 20th century

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J. H. C. Whitehead knownFor Whitehead product in homotopy theory