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Mephist

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Arghhh!!! :grimace: This is an example of intuitionistic dependently typed theory, corresponding to a non-trivial topological space. The previous one ...
January 23, 2020 at 05:27
WOW!!! I understand only partially what the terms mean: analytical continuation of a complex function has something to do with chaotic systems? Did I ...
January 23, 2020 at 03:33
To relate to something that probably you know better: the Riemann zeta function is related to the distribution of prime numbers: why complex functions...
January 23, 2020 at 00:53
Yes, exactly! Look for example at this: https://homotopytypetheory.org/ Well, not only is useful, but if you find a relation between apparently comple...
January 23, 2020 at 00:47
That's an example of the relation between logic and topology. A fiber bundle (topological space) can be interpreted as a set of propositions speaking ...
January 23, 2020 at 00:37
Here's the example of a fiber bundle that I promised. The BASE SPACE is constituted of 3 propositions (propositios are types): P1 := {A;B;C} P2 := {C;...
January 22, 2020 at 23:57
OK, I understand what you want to do. But in the case of fiber bundles you don't define the topology of the total space in terms of the topology of th...
January 22, 2020 at 05:30
The problem with your interpretation is that you don't consider variables. You build a model of propositional calculus ( https://en.wikipedia.org/wiki...
January 22, 2020 at 03:11
The underlying set is the set of all propositions. The fibers are sets of elements of our model. OK. Yes, unfortunately I am not able to follow your p...
January 21, 2020 at 22:55
:smile: Thanks for trying to help! But it's not so simple... I am afraid @"fishfry" has chosen the most complicated way to "build" a topos: the one th...
January 21, 2020 at 22:37
Part one: C is a category ( like A is an abelian group ) Part two: for each pair of objects of A, B there is a "product object" P ( like for each pair...
January 21, 2020 at 05:38
OK, as I said, I'll get to fiber bundles on the next episode.. :smile:
January 21, 2020 at 05:21
Yes, well, the point is that you cannot "count" the objects of a category. You cannot distinguish between isomorphic objects. There is no "equality" r...
January 21, 2020 at 05:17
That's pretty standard old-fashioned model theory and first order logic (the topology is irrelevant: forget about open sets and take simply the set of...
January 21, 2020 at 05:12
Yes, but that correspondence is evident only in a dependent type theory, where you can make sense of the topology defined on your set of propositions ...
January 21, 2020 at 04:44
Yes!
January 21, 2020 at 04:33
Here's the explanation in straightforward terms: a topos is an "extension" of the category of sets. ( probably it should have been called "setos" :gri...
January 21, 2020 at 00:14
About the randomness of sequences, I think a good definition is the following one: a sequence is random if it cannot be generated by a program shorter...
January 20, 2020 at 02:20
Hmm... :chin: You want a topological space for classical logic. OK, a topological space is a set of all subsets of an "universal" set. - The elements ...
January 19, 2020 at 12:40
It wasn't inaccurate, it was a particular case, as you usually do when you give an example.. Yes, but you can easily find the precise definitions on W...
January 19, 2020 at 07:58
A subobject classifier is a pair of an object and an arrow {Omega, "true": T->Omega} with the following property: every monomorphism m: A->B in the ca...
January 19, 2020 at 07:32
Well, OK, but I don't know which point is the halfway...
January 19, 2020 at 06:37
Can you give me some references?
January 19, 2020 at 06:34
OK, I'll drop this topic. Probably nobody is interested... :sad:
January 19, 2020 at 06:33
OK
January 19, 2020 at 06:28
Maybe yes. I see sheaves as a comma category, basically.
January 19, 2020 at 06:28
I know Coq. And I know type theory because it's the logic implemented in coq. And type theory is the internal logic of a topos. I read some books abou...
January 19, 2020 at 06:21
Prop is the type of propositions. It's an object of the category. {Prop, true} is the subobject classifier of the topos
January 19, 2020 at 06:15
Nat is the type of natural numbers. Types are represented by objects of the category, derivations are represented by the arrows. That's in the book fr...
January 19, 2020 at 06:14
Well, if you want the exact definition of sheaf I can copy it from the book on category theory that I posted you yesterday. I don't know all possible ...
January 19, 2020 at 06:06
OK, fair point. Sorry for the intrusion! :sad:
January 19, 2020 at 05:51
I am for the second one: conformity with the facts of the world.
January 19, 2020 at 05:45
OK, you are right! What I wanted to point out is that the sentence "there is an uncountable number of sequences", when expressed in the forall-exists ...
January 19, 2020 at 02:19
Let me just give you just some examples: "x >= 3" is a fibration from the object Nat to the subobject classifier Prop. The proposition "5 >= 3" is a f...
January 18, 2020 at 21:10
OK, I'll start from the example: 1. Let's call Unit our terminal object. 2. Let's call Prop the object that is part of our subobject classifier (usual...
January 18, 2020 at 19:40
I noticed that I was mentioned here, so I started to read this thread from the beginning. And I realized that probably this is the perfect example to ...
January 18, 2020 at 15:51
Yes.
January 18, 2020 at 05:17
No, I like "normal" mathematics: no computers involved. But having a theorem-prover as Coq to be able to verify if you can really write a proof of wha...
January 18, 2020 at 04:55
I agree with you. But now I am too curious: which theorems did you prove?
January 18, 2020 at 04:47
Yes.
January 18, 2020 at 04:42
Yes! I should have added a formal definition, but I have an aversion to writing symbols on this site :confused: I added a link with a clear picture, I...
January 18, 2020 at 04:39
I know about measure theory since when I was at high school (I always liked that stuff), and I heard that sentence about the probability to find a rat...
January 18, 2020 at 04:33
Exactly! We are speaking about two different kinds of "representations" of logic.
January 18, 2020 at 04:22
OK, never mind. Sorry for continuing to repeat the same things!
January 18, 2020 at 04:14
A sheaf is a topos at the same way as a set is a topos: it's the "trick" of the Yoneda embedding! :smile: do you understand now? (sorry: bad example.....
January 18, 2020 at 04:06
Yes, I work as a programmer. And yes, a formal proof completely misses the essence of a proof: it's "meaning". I don't beprove lieve mathematics is ch...
January 18, 2020 at 04:00
OK, that's the "like I'm five" explanation: A topos is a category that "works" as the category of sets, but is not built using a set of rules that ope...
January 18, 2020 at 00:13
Re-reading your question I just realized that probably my answer about homotopy type theory could be misleading: this is really a weird and interestin...
January 17, 2020 at 23:18
Yes, it seems very strange! Here's the "quick and dirty" explanation: A sheaf S over a topological space X is a "fiber bundle", where the fibers over ...
January 17, 2020 at 22:25
Probably you think that I completely missed the "meaning" of what a mathematical proof is. But that's the way computers (formal logic systems) see pro...
January 17, 2020 at 20:13