User Peter Smith

37 votes

3 answers

2k views

Simple/natural questions in group theory whose answers depend on set theory

asked Mar 5, 2020 at 9:00

26 votes

5 answers

2k views

Alternative set theories

soft-question set-theory education alternative-set-theories

asked Mar 15, 2013 at 21:20

18 votes

1 answer

900 views

Primitive recursive function which isn't $\Delta_0$

logic computability recursion

asked Apr 17, 2013 at 14:52

17 votes

2 answers

437 views

Two styles of semantics for a first-order language: what's to choose?

logic predicate-logic

asked Sep 1, 2013 at 19:51

17 votes

2 answers

935 views

The (un)decidability of Robinson-Arithmetic-without-Multiplication?

logic

asked Jul 21, 2014 at 10:23

17 votes

2 answers

695 views

You've got your head round Basic Category Theory: why look at monads next?

reference-request soft-question category-theory

asked Nov 11, 2015 at 15:45

16 votes

2 answers

330 views

Natural isomorphisms: what is the status now of "the Eilenberg/Mac Lane Thesis"?

category-theory soft-question natural-transformations

asked Jul 9, 2015 at 13:11

16 votes

3 answers

2k views

What's a good motivating example for the concept of a slice category?

category-theory intuition examples-counterexamples big-list motivation

asked Oct 28, 2014 at 0:11

16 votes

1 answer

633 views

Mendelson's $\mathit{Mathematical\ Logic}$ and the missing Appendix on the consistency of PA

reference-request logic math-history

asked Jan 27, 2013 at 15:20

13 votes

1 answer

282 views

Is there a quicker argument from the HBL derivability conditions to the equivalence of fixed points of $\neg\Box$ to $\mathsf{Con}$?

logic incompleteness

asked Jan 20, 2013 at 17:34

12 votes

1 answer

539 views

Olympiad-style question about functions satisfying condition $f(f(f(n))) = f(n+1) + 1$

elementary-number-theory functions

asked Jan 27, 2015 at 20:34

11 votes

0 answers

236 views

Elementary references on Robinson Arithmetic, Prim. Recursive fns etc.

reference-request logic computability incompleteness arithmetic-functions

asked Jan 28, 2014 at 19:55

10 votes

1 answer

208 views

Who first explicitly noted that second-order logic is unaxiomatizable?

logic math-history

asked Nov 22, 2012 at 13:15

9 votes

1 answer

513 views

Do hom-sets really live in the category Set?

reference-request soft-question category-theory

asked Jan 20, 2015 at 19:34

8 votes

1 answer

233 views

What is a nice "naturally occurring" example of an arrow category?

category-theory

asked Oct 11, 2015 at 14:56

8 votes

1 answer

673 views

Introductions to intuitionistic logic?

logic reference-request intuitionistic-logic

asked Dec 8, 2019 at 21:34

7 votes

1 answer

139 views

Survey of varieties of non-standard analysis?

reference-request nonstandard-analysis

asked Feb 2, 2016 at 13:05

7 votes

1 answer

843 views

Symbol for assignment of a truth-value?

logic notation

asked Jan 13, 2018 at 19:16

7 votes

1 answer

271 views

Recent sets of notes/newly available online books on category theory?

reference-request category-theory self-learning online-resources

asked Feb 1, 2018 at 9:04

7 votes

1 answer

507 views

How to prove adjunctions compose (via units and counits)?

category-theory

asked Jun 6, 2015 at 21:29

6 votes

2 answers

358 views

Examples of functors that preserves products but not equalizers, and vice versa.

soft-question category-theory

asked Mar 25, 2015 at 22:41

6 votes

3 answers

137 views

Categories with some but not all exponentials

category-theory examples-counterexamples

asked Sep 1, 2015 at 12:55

5 votes

2 answers

678 views

A proof that right adjoints preserve limits?

category-theory limits-colimits adjoint-functors

asked Jul 14, 2015 at 21:00

5 votes

0 answers

207 views

The counted is to the countable as the ??? is to the (order)-isomorphic.

elementary-set-theory terminology

asked Aug 23, 2013 at 16:23

4 votes

2 answers

1k views

Introductory example(s) of a functor that is full but not faithful

category-theory examples-counterexamples big-list

asked Oct 20, 2014 at 15:06

4 votes

0 answers

81 views

Symbol for function composition [duplicate]

functions notation math-history

asked Jan 26, 2013 at 8:54

4 votes

0 answers

173 views

Cutest proof that PA proves its finitely axiomatised subtheories are consistent?

reference-request logic

asked Aug 3, 2012 at 10:27

4 votes

3 answers

243 views

Free variables, parameters, dummy names -- what policy to choose?

logic quantifiers

asked Mar 14, 2018 at 15:47

4 votes

1 answer

170 views

Mathematicians endorsing platonism -- examples?

big-list foundations philosophy

asked Feb 27 at 10:22

3 votes

0 answers

39 views

Replacement and implementation-independence in set theory

set-theory

asked Jun 27 at 17:41

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37 Questions

Simple/natural questions in group theory whose answers depend on set theory

Alternative set theories

Primitive recursive function which isn't $\Delta_0$

Two styles of semantics for a first-order language: what's to choose?

The (un)decidability of Robinson-Arithmetic-without-Multiplication?

You've got your head round Basic Category Theory: why look at monads next?

Natural isomorphisms: what is the status now of "the Eilenberg/Mac Lane Thesis"?

What's a good motivating example for the concept of a slice category?

Mendelson's $\mathit{Mathematical\ Logic}$ and the missing Appendix on the consistency of PA

Is there a quicker argument from the HBL derivability conditions to the equivalence of fixed points of $\neg\Box$ to $\mathsf{Con}$?

Olympiad-style question about functions satisfying condition $f(f(f(n))) = f(n+1) + 1$

Elementary references on Robinson Arithmetic, Prim. Recursive fns etc.

Who first explicitly noted that second-order logic is unaxiomatizable?

Do hom-sets really live in the category Set?

What is a nice "naturally occurring" example of an arrow category?

Introductions to intuitionistic logic?

Survey of varieties of non-standard analysis?

Symbol for assignment of a truth-value?

Recent sets of notes/newly available online books on category theory?

How to prove adjunctions compose (via units and counits)?

Examples of functors that preserves products but not equalizers, and vice versa.

Categories with some but not all exponentials

A proof that right adjoints preserve limits?

The counted is to the countable as the ??? is to the (order)-isomorphic.

Introductory example(s) of a functor that is full but not faithful

Symbol for function composition [duplicate]

Cutest proof that PA proves its finitely axiomatised subtheories are consistent?

Free variables, parameters, dummy names -- what policy to choose?

Mathematicians endorsing platonism -- examples?

Replacement and implementation-independence in set theory