[HoTT] Re: Free higher groups

[Ulrik Buchholtz <ulrikbuchholtz@gmail.com>]

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Congratulations, that's really great!

And indeed, this is going to be very useful in general: for instance, 
together with Tom de Jong and Egbert Rijke, we used your work as an input 
to give a short constructive proof of the non-triviality of the Higman 
group. I'll talk about this in Vienna on Sunday.

Best wishes,
Ulrik


On Friday, April 21, 2023 at 12:04:20 PM UTC+2 cod...@gmail.com wrote:

> Dear all,
>
> I'm happy to announce a solution to one of the oldest open problems in 
> synthetic homotopy theory: the free higher group on a set is a set.
>
> The proof proceeds by describing path types of pushouts as sequential 
> colimits of pushouts, much like the James construction. This description 
> should be useful also in many other applications. For example it gives a 
> straightforward proof of Blakers-Massey.
>
> Best wishes,
> David
>

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