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A Weiss–Williams theorem for spaces of embeddings and the homotopy type of spaces of long knots

Samuel Muñoz-Echániz

Geometry & Topology 30 (2026) 701–780
Abstract

We establish a pseudoisotopy result for embedding spaces in the line of that of Weiss and Williams for diffeomorphism groups. In other words, for P M an embedding of codimension at least 3, we describe the difference in a range of homotopical degrees between the spaces of block and ordinary embeddings of P into M as a certain infinite loop space involving the relative algebraic K-theory of the pair (M,M P). This range of degrees is the so-called concordance embedding stable range, which, by recent developments of Goodwillie, Krannich, and Kupers, is far beyond that of the aforementioned theorem of Weiss and Williams.

We use this result to obtain split fibre sequences in the concordance embedding stable range, with explicit analysable base and fibre, which determine the homotopy type of spaces of long knots of codimension at least 3. This leads to explicit computations of homotopy groups, including torsion information, in that range. In doing so, we carry out an extensive analysis of certain geometric involutions in algebraic K-theory that may be of independent interest.

Keywords
embedding space, pseudoisotopy, long knot
Mathematical Subject Classification
Primary: 18F50, 19D10, 57R40, 57R80, 58D10
Secondary: 57S05
References
Publication
Received: 17 May 2024
Revised: 20 August 2025
Accepted: 26 September 2025
Published: 16 March 2026
Proposed: Nathalie Wahl
Seconded: Haynes R Miller, Roman Sauer
Authors
Samuel Muñoz-Echániz
Centre for Mathematical Sciences
University of Cambridge
Cambridge
United Kingdom
Mathematics Department
Massachusetts Institute of Technology
Cambridge, MA
United States

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