nLab
h-principle

Gromovs homotopy principle or h-principle

Gromov’s homotopy principle or h-principle

Definition

Let p:XBp: X\to B be a smooth fiber bundle and the space X (r)X^{(r)} of rr-jets of sections of pp; there is an induced projection X (r)BX^{(r)}\to B which makes it into a smooth bundle.

One considers a fixed partial differential relation (see differential equation) which is a subset RX (r)R\subset X^{(r)}. One is interested in finding formal sections ss of X (r)BX^{(r)}\to B whose image is in RR, and which are, in addition, holonomic sections, i.e. equal to the rr-jet J f rJ_f^r of a C rC^r-section ff of p:XBp:X\to B. One says that RR satisfies the h-principle if every formal section of RR is homotopic to a holonomic section within the appropriate topological space of formal sections.

Applications and examples

For example, in the case of holomorphic fiber bundles RR may be the Cauchy-Riemann relation, thus the question is if there is a deformation of a continuous section into a holomorphic one. In other words, one wants to reduce the problem of existence of maps of certain type to the analogous topological problem. Applications include results on the spaces of immersions, submersions, k-mersions, holomorphic maps, symplectic and isometric embeddings, contact structures and so on.

Mikhail Gromov demonstrated the result that if BB is an open nn-manifold, and if RR is open as a subspace of X (r)X^{(r)} and is Diff(B)Diff(B)-invariant, then RR satisfies the hh-principle (EliasMisha 01, sec 2.1, Haefliger 71, p. 128)

General methods

Gromov introduced many techniques of proving the h-principle including the method of microflexible/continuous sheaves, the methods of convex integration and the removal of singularities.

References

  • eom: H-principle, convex integration; wikipedia: homotopy principle

  • MathOverflow: h-principle-and-pdes

  • Mikhail Gromov, Partial differential relations, Ergebn. Math. Grenzgeb. (3), 9, Springer (1986)

  • M. Gromov, A topological technique for the construction of solutions of differential equations and inequalities, Proc. Int. Congress Math. Nice 1970, vol. 2, 221-225, djvu w OCR, pdf

  • M. Gromov, Papers on h-principle: geometric methods for solving partial differential equations/inequalities and the homotopy structure in the spaces of their solutions, list (with some links)

  • Y. Eliashberg, N. Mishachev, Introduction to the h-principle, Graduate Studies in Mathematics 48. Amer. Math. Soc. 2002 gBooks

  • Y. Eliashberg, N. Mishachev, Holonomic approximation and Gromov’s h-principle, arXiv:math/0101196

  • André Haefliger, Lectures on the Theorem of Gromov, Proceedings of Liverpool Singularities Symposium, II (1969/1970), p. 128-141. Lecture Notes in Math. 209, Springer, Berlin, 1971 (pdf).

  • John Francis, The h-principle in topology (overview pdf)

  • Andrés Angel, Johannes Ebert, Gromov’s h-principle and its applications research seminar, 2010, outline pdf (with useful bibliography)

  • London h-principle learning seminar

Last revised on May 22, 2019 at 15:37:01. See the history of this page for a list of all contributions to it.