Thom isomorphism


Manifolds and cobordisms



Special and general types

Special notions


Extra structure





For HH a multiplicative cohomology theory, and VXV \to X a vector bundle of rank nn, which is HH-orientable, the Thom isomorphism is the isomorphism

()u:H (X)H +n(Th(V)). (-) \cdot u : H^\bullet(X) \stackrel{\simeq}{\to} H^{\bullet + n}(Th(V)) \,.

from the cohomology of XX to the cohomology of the Thom space Th(V)Th(V), induced by multiplication with a Thom class uH n(Th(V))u \in H^n(Th(V)).

We think of this from left to right as wedge-ing with a generalized volume form on the fibers, and from right to left as performing fiber integration.


A fully general abstract discussion is around page 30,31 of (ABGHR).



  • The Thom isomorphism is used to define fiber integration of multiplicative cohomology theories.


The original reference is

  • René Thom, Quelques propriétés globales des variétés différentiables Comm. Math. Helv. , 28 (1954) pp. 17–86

  • W. Cockcroft, On the Thom isomorphism Theorem Mathematical Proceedings of the Cambridge Philosophical Society (1962), 58 (pdf)

A review is in

  • John Francis, Topology of manifolds, course notes (2010) (web)

    Lecture 3 Thom’s theorem (notes by A. Smith) (pdf)

A discussion in differential geometry with fiberwise compactly supported differential forms is around theorem 6.17 of

A comprehensive general abstract account for multiplicative cohomology theories in terms of E-infinity ring spectra is in

An alternative simple formulation in terms of geometric cycles as in bivariant cohomology theory is in

  • Martin Jakob, A note on the Thom isomorphism in geometric (co)homology (arXiv:math/0403540)

See also

  • A. Dold, Relations between ordinary and extraordinary homology , Colloq. Algebraic Topology, August 1–10, 1962 , Inst. Math. Aarhus Univ. (1962) pp. 2–9

  • Yu.B. Rudyak, On the Thom–Dold isomorphism for nonorientable bundles Soviet Math. Dokl. , 22 (1980) pp. 842–844 Dokl. Akad. Nauk. SSSR , 255 : 6 (1980) pp. 1323–1325

  • R.M. Switzer, Algebraic topology - homotopy and homology , Springer (1975)

  • (Planetmath) Thom space, Thom class, Thom isomorphism theorem

Revised on July 5, 2013 19:08:11 by Urs Schreiber (