Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 2926

first-order and higher-order logic, model theory, set theory, proof theory, computability theory, formal languages, definability, interplay of syntax and semantics, constructive logic, intuitionism, philosophical logic, modal logic, completeness, Gödel incompleteness, decidability, undecidability, theories of truth, truth revision, consistency.

20 votes

What is neutral constructive mathematics

You'll probably have better luck with the phrase "intuitionistic higher-order logic" (IHOL). A good place to start is the book by Lambek and Scott, Introduction to Higher Order Categorical Logic. But …
Todd Trimble's user avatar
  • 53.3k
8 votes

Categories of recursive functions

Regarding question 1.: it's hard to find the statement spelled out in black and white in the literature. Apparently Gavin Wraith proved it in unpublished notes titled "Notes on arithmetic universes an …
Todd Trimble's user avatar
  • 53.3k
10 votes
Accepted

Primitive recursive arithmetic via universal algebra

According to unpublished notes by Gavin Wraith ("Notes on arithmetic universes and Gödel incompleteness theorems" (1985)), PRA can be described as an equational theory or as a Lawvere theory, and is a …
Todd Trimble's user avatar
  • 53.3k
7 votes
Accepted

What is some good introduction to lambda calculus?

There is, of course, the very famous book by Barendregt, The Lambda Calculus, Its Syntax and Semantics (Studies in Logic and the Foundations of Mathematics, Volume 103). Revised Edition, North-Holl …
Todd Trimble's user avatar
  • 53.3k
3 votes

Does the exact pair phenomenon for partial orders occur in your area of mathematics?

In trying to understand better a certain weak choice axiom, I once concocted an example in sheaf theory which involves an exact pair in the sense of this question, without knowing it was a "thing" els …
Todd Trimble's user avatar
  • 53.3k
15 votes
Accepted

Logical complexity of algebraically closed fields

From Dirk van Dalen's Logic and Structure: the theory of algebraically closed fields is not finitely axiomatizable (see page 109 and preceding).
Todd Trimble's user avatar
  • 53.3k
2 votes

In which sense "closure" is a closure?

Actually, there is a topological meaning to closure of logical formulas, if one represents formulas by string diagrams. A description of such a string diagram calculus, interpreting Peirce's existenti …
Todd Trimble's user avatar
  • 53.3k
38 votes
5 answers
5k views

Does "compact iff projections are closed" require some form of choice?

There are many equivalent ways of defining the notion of compact space, but some require some kind of choice principle to prove their equivalence. For example, a classical result is that for $X$ to be …
2 votes

Injecting premises into two implicational premises connected by a tensor (multiplicative con...

Well, this is very easy, but because linear logic might be considered a little too specialized for Mathematics StackExchange, I'll answer. Since the natural semantics of MLL (multiplicative linear l …
Todd Trimble's user avatar
  • 53.3k
18 votes

Is there a natural bijection from $\mathbb{N}$ to $\mathbb{Q}$?

To my aesthetic sensibilities, the Calkin-Wilf tree response is pretty close to optimal, but I'll add some additional glosses. (I only noticed later that Vladimir Dotsenko wrote something similar befo …
Todd Trimble's user avatar
  • 53.3k
4 votes

Brouwer vs. Cantor

Troelstra is a well-known exponent of intuitionism. Here are two online articles that contain philosophical and historical material that may be useful to you: Remarks on Intuitionism and the Philos …
Todd Trimble's user avatar
  • 53.3k
1 vote

Self-similarity for simple algebraic structures

I haven't read your description (and don't know the area well enough) to make an evaluation, but as far as algebraic treatments go... have you seen Tom Leinster's Theory of Self-Similarity? This is ba …
Todd Trimble's user avatar
  • 53.3k
3 votes

"Introduction to mathematical logic" book from a formalist perspective

I don't know of logic textbooks which adopt an explicitly formalist viewpoint (which is not to say I think none exist), but for what it's worth, I'd say that books on categorical logic tend not to ado …
Todd Trimble's user avatar
  • 53.3k
44 votes
Accepted

Completion of a category

Yes, it's a general construction which is related to so-called Isbell conjugation. Let $C$ be a small category. It is well-known that the free colimit cocompletion is given by the Yoneda embedding i …
Todd Trimble's user avatar
  • 53.3k
8 votes
Accepted

Adjoining an arrow to a CCC

They mean this: given a cartesian closed $\mathcal{A}$ and objects $A, B$ of $\mathcal{A}$, the inclusion $i: \mathcal{A} \to \mathcal{A}[x]$ is universal with respect to strict cartesian closed funct …
Todd Trimble's user avatar
  • 53.3k

15 30 50 per page