### Pseudo-isotopies of 4-manifolds

One of the landmark results about the topology of 4-manifolds is Freedman’s proof of the 4-dimensional Poincaré conjecture. The problem with this result was that after some time people claiming to understand its proof disappeared, so that in the last decade the validity of this result was openly questioned (e.g., link). In the end, a … Continue reading "Pseudo-isotopies of 4-manifolds"

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