From: Martin Escardo <escardo...@googlemail.com>
To: stre...@mathematik.tu-darmstadt.de
Cc: "HomotopyT...@googlegroups.com" <HomotopyT...@googlegroups.com>
Subject: Re: [HoTT] Does MLTT have "or"?
Date: Wed, 3 May 2017 15:25:47 +0100 [thread overview]
Message-ID: <d43ff886-58d8-29ce-b24e-c74d9a22c93c@googlemail.com> (raw)
In-Reply-To: <20170503105509.GB12588@mathematik.tu-darmstadt.de>
On 03/05/17 11:55, stre...@mathematik.tu-darmstadt.de wrote:
>> (4) What is a model of intensional MLTT with a universe such that
>> ||-|| doesn't exist?
>
> In my 1992 TCS paper I have constructed an impredicative universe
> within Asm(K_1) (separated objects of effective topos) which is not
> reflective. The universe consists of all powers of N together with the
> initial object. All its elements are empty or contain infinitely many
> global elements.
>
> But or is definable `a la Russel-Prawitz.
What you are saying is that there is model where general propositional
truncations don't exist, but "or" does. Right?
How difficult is to get a model where "or" doesn't exist either?
Best,
Martin
next prev parent reply other threads:[~2017-05-05 4:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-02 9:09 Martin Escardo
2017-05-02 19:04 ` [HoTT] " Michael Shulman
2017-05-03 6:47 ` Martin Escardo
2017-05-12 18:10 ` Martin Escardo
2017-05-12 18:41 ` Martin Escardo
2017-05-13 21:46 ` Michael Shulman
2017-05-14 9:54 ` stre...
2017-05-16 6:20 ` Michael Shulman
2017-05-03 10:55 ` Thomas Streicher
2017-05-03 14:25 ` Martin Escardo [this message]
2017-05-03 14:48 ` Thomas Streicher
2017-05-03 15:04 ` Martin Escardo
2017-05-03 12:17 ` Andrew Polonsky
2017-05-03 12:24 ` [HoTT] " Martin Escardo
2017-05-03 12:24 ` Michael Shulman
2017-05-06 13:51 ` Andrew Swan
2017-05-07 13:49 ` [HoTT] " Martin Escardo
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