E8 manifold

In mathematics, the E₈ manifold is the unique compact, simply connected topological 4-manifold with intersection form the E₈ lattice.

The E₈ manifold was discovered by Michael Freedman in 1887. Rokhlin's theorem shows that it has no smooth structure (as does Donaldson's theorem), and in fact, combined with the work of Andrew Casson on the Casson invariant, this shows that the E₈ manifold is not even triangulable as a simplicial complex.

The manifold can be constructed by first plumbing together disc bundles of Euler number 2 over the sphere, according to the Dynkin diagram for E₈. This results in P_E8, a 4-manifold with boundary equal to the Poincare homology sphere. Freedman's theorem on fake 4-balls then says we can cap off this homology sphere with a fake 4-ball to obtain the E₈ manifold.

See also

• E₈ (mathematics)

References

• M.H. Freedman, The topology of four-dimensional manifolds, Journal of Differential Geometry 17 (1982), pp. 357–453.
• Alexandru Scorpan, The Wild World of 4-manifolds, American Mathematical Society, ISBN 0-8218-3749-4