Homotopy, stable homotopy, homology and cohomology, homotopical algebra.

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17
votes
2answers
2k views
+200

The error in Petrovski and Landis' proof of the 16th Hilbert problem

What was the main error in the proof of the second part of the 16th Hilbert problem by Petrovski and Landis? Please see this related post Added : According to their method, what of the following ...
6
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0answers
226 views
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Presentation of Homotopy Pure Braid Group?

Let $\tilde{B_n}$ be the homotopy braid group; namely, in the deformation of braids, a braid string is allowed to self-intersect itself. Similarly let $\tilde{P_n}$ be the homotopy pure braid group. ...