From: "Martín Hötzel Escardó" <"escardo..."@gmail.com>
To: Homotopy Type Theory <HomotopyT...@googlegroups.com>
Subject: Re: [HoTT] Voevodsky obituary in Nature
Date: Tue, 7 Nov 2017 15:11:58 -0800 (PST) [thread overview]
Message-ID: <380b537f-f78f-4bbb-9357-c55e8cd60b47@googlegroups.com> (raw)
In-Reply-To: <fa3b9780-31b2-44d6-8a39-e771e8615ff1@googlegroups.com>
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On Tuesday, 7 November 2017 22:49:30 UTC, Martín Hötzel Escardó wrote:
>
>
>
> On Tuesday, 7 November 2017 21:50:24 UTC, Dimitris Tsementzis wrote:
>>
>> Dan,
>>
>> It is an interesting idea to refer to univalence as a “mechanism” rather
>> than an “axiom”.
>>
>> Even if you did it for expository reasons, I believe that in certain
>> contexts it is a good phrase to adopt.
>>
>
> I very much like this way of expression, too, even though univalence
> became a mechanism for the first time with cubicaltt.
>
> Nevertheless, although Vladimir certainly didn't have a mechanism for
> univalence, he envisioned its possibility, and even formulated a conjecture
> that is still unsettled, namely that if univalence implies that there is a
> *number* n:N with a property P(n), then we can find, metatheoretically,
> using an algorithm, a *numeral* n':N (a closed term of type N) and a proof
> that univalence implies P(n').
>
The conjecture said that we can find a numeral n':N and a proof that
univalence implies n=n' .
Here is what he actually conjectured:
"
Conjecture 1 There is a terminating algorithm which for any term nn of type
nat constructed
with the use of the univalence axiom outputs a pair (nn 0 , pf ) where nn 0
is a term of type nat
constructed without the use of the univalence axiom and pf is a term of
type paths nat nn nn 0 (i.e.
a proof that nn 0 = nn). The term pf may use the univalence axiom.
"
http://www.math.ias.edu/vladimir/files/univalent_foundations_project.pdf
Martin
No mechanism for univalence can currently provide that, as far as I know.
>
> Martin
>
>
>>
>> Dimitris
>>
>> On Nov 7, 2017, at 16:40, Daniel R. Grayson <daniel...@gmail.com>
>> wrote:
>>
>> See https://www.nature.com/articles/d41586-017-05477-9
>>
>> --
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>>
>>
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prev parent reply other threads:[~2017-11-07 23:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 21:40 Daniel R. Grayson
2017-11-07 21:51 ` [HoTT] " Dimitris Tsementzis
2017-11-07 22:49 ` Martín Hötzel Escardó
2017-11-07 23:11 ` Martín Hötzel Escardó [this message]
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