Math 2.0

Algebraic topology Stable homotopy theory and generalized cohomology Counterexample

Telescope conjecture

Builds on Ravenel conjecturesChromatic homotopy theorySpectrum

Counterexample

Fix a prime pp and n≥1n \ge 1. Let XX be a finite pp-local spectrum of type nn. Let v ⁣:ΣdX→Xv \colon \Sigma^d X \to X be a vnv_n self-map, as given by the periodicity theorem among the Ravenel conjectures. The telescope of vv is the homotopy colimit v−1X=hocolim⁡(X→vΣ−dX→vΣ−2dX→⋯ ).v^{-1} X = \operatorname{hocolim}\left( X \xrightarrow{v} \Sigma^{-d} X \xrightarrow{v} \Sigma^{-2d} X \to \cdots \right). The telescope conjecture asserted that the natural map v−1X→LK(n)Xv^{-1} X \to L_{K(n)} X is an equivalence, where LK(n)L_{K(n)} is Bousfield localization at the nn-th Morava K-theory. The conjecture is false for every prime pp and every height n≥2n \ge 2. In 2023 Burklund, Hahn, Levy and Schlank showed that for such pp and nn the map v−1X→LK(n)Xv^{-1} X \to L_{K(n)} X is not an equivalence.

Remarks

The telescope v−1Xv^{-1} X does not depend on the choice of vv, and its Bousfield class depends only on nn; the localization at it is written LT(n)L_{T(n)}. So the conjecture says LT(n)=LK(n)L_{T(n)} = L_{K(n)}. At height 11 the conjecture is true: Mahowald proved it for p=2p = 2 and Miller for pp odd. The counterexample of Burklund, Hahn, Levy and Schlank uses algebraic K-theory to build T(n)T(n)-local spectra that are not K(n)K(n)-local. It shows that the homotopy of telescopes is genuinely larger than what K(n)K(n)-local computations see.

Reading path

To understand this page from the ground up, read these 10 pages in order. The foundations come first.

Show the path as a graph
Each page uses the pages above it. The colour of the bar on a box shows how strong the evidence is, and the box also gives it as text. The list has the same pages.
  • no evidence level
  1. Chromatic homotopy theory concept
  2. Complex cobordism concept
  3. Prime number concept
  4. Ring spectrum concept
  5. Spectrum concept
  6. Stable homotopy groups of spheres concept
  7. Nishida nilpotence theorem statement
  8. Nilpotence theorem statement
  9. Ravenel conjectures statement
  10. Telescope conjecture counterexample

Further reading

  1. Web https://en.wikipedia.org/wiki/Ravenel's_conjectures
About this page
Tag68650624FF
URIm2://68650624FF
Kindcounterexample
WritingW0 stub
MSC55P42, 55Q51, 55P60
UsesRavenel conjectures, Chromatic homotopy theory, Spectrum
Changed2 November 2026

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