Posts

About Logic Interview with Emily Riehl

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51:47 Question about set theory vs type theory. I don't know that there was ever a split. The impression I get is that type theory was developed as a way to reason formally about set theory, and then that structure turned out to fit well with constructive mathematics and intuitionistic logic. So the people who study type theory tend to be constructivists. See  About Logic - Is Mathematics a Story?  and  Andrej Bauer - Models of intuitionism and computability .  Subscribe to  About Logic . 

FUTO FUBS and the Everything App

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From  Eron Woolf on Why Open Source is Failing : I posted something on the FUTO Zulip and thought I'd copy it here: Hello FUTO types, I was just rewatching the short talk by Matt Mikhailov and Vincent McKibbon on open hardware blues https://youtu.be/YLn4vnfchaE and the discussion with Daniel C. on the Rockchip bringup https://youtu.be/5klMcYG-AP0 and I thought I'd post another ten cents worth here. It's not only the directly connected hardware that's being locked down, it's the network infrastructure too. Looking at the crazy stuff that people have to do to "punch holes" so that they can send and receive data peer-to-peer without publicising an IP address. This is in a sense dual to the problem of locked-down hardware, and they actually exacerbate each other. There are security vulnerabilities in the proprietary hardware and firmware, and the networks will route hostile traffic to compromise the crappy router your ISP installed in your house, but that s...

Olive Badger on Masters of the Universe and Men's Mental Health Awareness Month

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Andrej Bauer - Models of intuitionism and computability

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I got a bit lost there, ... but it does sound like there are a lot of things you can say about computability beyond just that "uncomputable functions exist".  It also sounds like Andy Pitts doesn't like modal logic.  I wonder what the quote was that he ended the talk with. I think it was something Jaap Van Oosten wrote somewhere. See  Basic subtoposes of the effective topos  (2013) by Sori Lee and Jaap van Oosten. Subscribe to  De KNAW . Here's a May 2022 talk on the countable reals. Subscribe to Topos Institute . After listening to these two talks last night I dreamed that someone was explaining to me how you could build computational circuits using a kind of "co-clocking". In this scheme the clock was an index into a type which was the successive ticks, and it meant that there was a notion of continuity in temporal evolution which was not the sort of thing Albert Einstein would have immediately understood. It was a really interesting dream! See David Albe...

David Albert Talking Complete Nonsense

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I am having serious trouble listening to this stream of complete crap he's talking. I have only managed an hour so far, with a few breaks. My comment : 17:41 I can't take seriously statements like this one "The laws of Newtonian theory determine the complete physical condition of the world, given the complete physical condition of the world at some earlier time." This was an hypothetical argument made by Laplace and it's become something else entirely, solely through mindless repetition ever since. Nobody seriously believed you could learn anything about the world under this hypothesis, did they? It reduces knowledge to infinite initial information and time becomes meaningless, therefore knowledge cannot change. That's just not an interesting idea at all. No meaningful theory, complete or otherwise, can start from material and information without any understanding subject for whom that information is meaningful. Any such theory is vacuous. These vacuous theo...

Beavers in Europe

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Sounds like this heatwave in Europe and the UK would have been much easier to handle if there were a lot more beavers.  Subscribe to Hope .

FUTO Notes and Rhombus Announcements

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See https://notes.futo.tech/ Subscribe to FUTO .   See  https://rhombus-lang.org/ Subscribe to Racket . 

Charlotte Moser on Data Assimilation

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My comment : There is this 2000 paper "Information theory explanation of the fluctuation theorem, maximum entropy production and self-organized criticality in non-equilibrium stationary states" by Roderick C. Dewar which is really insightful, I think, but I found it quite hard to understand at first. He deals with the problem of defining what are the parameters of the macroscopic model without referring to any details of the microscopic system: so the reproducible macroscopic behaviour is described entirely in terms of expectation values on the underlying distributions in phase space.  The problem is that in a weather forecast it is not even clear what temperature/humidity could mean at the level of even a 10x10x10cm cube of air. So the idea of the accuracy of the measurements is kind of redundant since we have no way to even say what accuracy means!  See  Lyapunov Stability in Dynamical Systems  and  these other posts of mine .   Subscribe to Charlotte Mo...

Physics, Self Reference and Self Consciousness

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The muppets at 5:24 : Subscribe to  Oz Harms . See George Ellis and Ard Louis on top-down causation in  Why is Physics So Difficult? It seems like real life only because we know what it is supposed to be like:  And we know it ends well, ... Subscribe to Secondhand Movie Company . This post is a sequel to  About Logic - Is Mathematics a Story? What is a dependent type? What is a judgement? There's one missing, isn't there? What is a dependent judgement then? It's a judgement about a judgement, because it includes the turnstile. So how do you construct one? 21:06 . All these judgements are hypothetical : they depend upon some actual construction of the contexts Г in which they are valid, just like real life .  11:15 .   See the full list of talks here .  The two texts referred to ( 17:10 ): The HoTT Book, a.k.a. Homotopy type theory: Univalent foundations of mathematics . Introduction to Homotopy Type Theory by Egbert Rijke. Subscribe to  EPIT Spri...

Colleen Fazio Made a New Amp for Sale

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See  https://www.fazioelectric.com/amps . Subscribe to Fazio Electric .