cobordism theory = manifolds and cobordisms + stable homotopy theory/higher category theory
Concepts of cobordism theory
Pontrjagin's theorem (equivariant, twisted):
$\phantom{\leftrightarrow}$ Cohomotopy
$\leftrightarrow$ cobordism classes of normally framed submanifolds
$\phantom{\leftrightarrow}$ homotopy classes of maps to Thom space MO
$\leftrightarrow$ cobordism classes of normally oriented submanifolds
complex cobordism cohomology theory
flavors of bordism homology theories/cobordism cohomology theories, their representing Thom spectra and cobordism rings:
bordism theory$\;$M(B,f) (B-bordism):
relative bordism theories:
global equivariant bordism theory:
algebraic:
geometric representation theory
representation, 2-representation, ∞-representation
Grothendieck group, lambda-ring, symmetric function, formal group
principal bundle, torsor, vector bundle, Atiyah Lie algebroid
Eilenberg-Moore category, algebra over an operad, actegory, crossed module
Be?linson-Bernstein localization?
algebraic topology – application of higher algebra and higher category theory to the study of (stable) homotopy theory
An equivariant Pontrjagin theorem should generalize the Pontrjagin theorem from plain homotopy theory/cobordism theory to equivariant homotopy theory/equivariant cobordism theory:
Where the plain Pontrjagin theorem identifies the Cohomotopy of a differentiable manifold with its cobordism classes of normally framed submanifolds, an equivariant Pontrjagin theorem should identify equivariant Cohomotopy with fixed submanifolds whose normal framing inherits the linear representation of the given RO(G)-degree.
A fully general version of an equivariant Pontrjagin theorem is not known (?) and not expected to exist (?) because Thom's transversality theorem (which, in one formulation or another, underlies the proof of the ordinary Pontrjagin theorem) is known to fail equivariantly: Since equivariant functions need to send fixed points to fixed points, an equivariant map from an open neighbourhood of fixed points to an isolated fixed point has no equivariant deformation whatsoever, let along a regular one.
This problem with transversaliuty goes away when the action on the domain G-manifold is free action. In this case the equivariant Pontrjagin theorem in Cruickshank 99, Thm. 5.06.
Of course, this case is only “mildly equivariant”: When the $G$-action on the domain G-manifold is free then its equivariant homotopy theory should essentially reduce to plain homotopy theory of the quotient space. Indeed, Cruickshank 99, Cor. 6.0.13 identifies, in this case, equivariant Cohomotopy with cobordism classes of normally twisted-framed submanifolds, i.e. identifies it with the twisted Pontrjagin theorem (Cruickshank 03, Lemma 5.2) on the quotient.
The Pontryagin theorem, i.e. the unstable and framed version of the Pontrjagin-Thom construction, identifying cobordism classes of normally framed submanifolds with their Cohomotopy charge in unstable Borsuk-Spanier Cohomotopy sets, is due to:
Lev Pontrjagin, Classification of continuous maps of a complex into a sphere, Communication I, Doklady Akademii Nauk SSSR 19(3) (1938), 147-149
Lev Pontryagin, Homotopy classification of mappings of an (n+2)-dimensional sphere on an n-dimensional one, Doklady Akad. Nauk SSSR (N.S.) 19 (1950), 957–959 (pdf)
(both available in English translation in Gamkrelidze 86),
as presented more comprehensively in:
The Pontrjagin theorem must have been known to Pontrjagin at least by 1936, when he announced the computation of the second stem of homotopy groups of spheres:
Review:
Daniel Freed, Karen Uhlenbeck, Appendix B of: Instantons and Four-Manifolds, Mathematical Sciences Research Institute Publications, Springer 1991 (doi:10.1007/978-1-4613-9703-8)
Antoni Kosinski, chapter IX of: Differential manifolds, Academic Press 1993 (pdf, ISBN:978-0-12-421850-5)
John Milnor, Chapter 7 of: Topology from the differential viewpoint, Princeton University Press, 1997. (ISBN:9780691048338, pdf)
Mladen Bestvina (notes by Adam Keenan), Chapter 16 in: Differentiable Topology and Geometry, 2002 (pdf)
Michel Kervaire, La méthode de Pontryagin pour la classification des applications sur une sphère, in: E. Vesentini (ed.), Topologia Differenziale, CIME Summer Schools, vol. 26, Springer 2011 (doi:10.1007/978-3-642-10988-1_3)
Rustam Sadykov, Section 1 of: Elements of Surgery Theory, 2013 (pdf, pdf)
András Csépai, Stable Pontryagin-Thom construction for proper maps, Period Math Hung 80, 259–268 (2020) (arXiv:1905.07734, doi:10.1007/s10998-020-00327-0)
Discussion of the early history:
The (fairly straightforward) generalization of the Pontrjagin theorem to the twisted Pontrjagin theorem, identifying twisted Cohomotopy with cobordism classes of normally twisted-framed submanifolds, is made explicit in:
A general equivariant Pontrjagin theorem – relating equivariant Cohomotopy to normal equivariant framed submanifolds – remains elusive, but on free G-manifolds it is again straightforward (and reduces to the twisted Pontrjagin theorem on the quotient space), made explicit in:
In negative codimension, the Cohomotopy charge map from the Pontrjagin theorem gives the May-Segal theorem, now identifying Cohomotopy cocycle spaces with configuration spaces of points:
Peter May, The geometry of iterated loop spaces, Springer 1972 (pdf)
Graeme Segal, Configuration-spaces and iterated loop-spaces, Invent. Math. 21 (1973), 213–221. MR 0331377 (pdf)
c Generalization of these constructions and results is due to
Dusa McDuff, Configuration spaces of positive and negative particles, Topology Volume 14, Issue 1, March 1975, Pages 91-107 (doi:10.1016/0040-9383(75)90038-5)
Carl-Friedrich Bödigheimer, Stable splittings of mapping spaces, Algebraic topology. Springer 1987. 174-187 (pdf, pdf)
Thom's theorem i.e. the unstable and oriented version of the Pontrjagin-Thom construction, identifying cobordism classes of normally oriented submanifolds with homotopy classes of maps to the universal special orthogonal Thom space $M SO(n)$, is due to:
Textbook accounts:
The joint generalization of Pontryagin 38a, 55 (framing structure) and Thom 54 (orientation structure) to any family of tangential structures (“(B,f)-structure”) is first made explicit in
and the general statement that has come to be known as Pontryagin-Thom isomorphism (identifying the stable cobordism classes of normally (B,f)-structure submanifolds with homotopy classes of maps to the Thom spectrum Mf) is Lashof 63, Theorem C.
Textbook accounts:
Stanley Kochman, section 1.5 of: Bordism, Stable Homotopy and Adams Spectral Sequences, AMS 1996
Yuli Rudyak, On Thom spectra, Orientability and Cobordism, Springer 1998 (pdf)
Lecture notes:
John Francis, Topology of manifolds course notes (2010) (web), Lecture 3: Thom’s theorem (pdf), Lecture 4 Transversality (notes by I. Bobkova) (pdf)
Cary Malkiewich, Section 3 of: Unoriented cobordism and $M O$, 2011 (pdf)
Tom Weston, Part I of An introduction to cobordism theory (pdf)
See also:
Last revised on March 3, 2021 at 09:03:26. See the history of this page for a list of all contributions to it.