1
vote
1answer
47 views

Types realized in ultrapowers consisting of definable functions

Let $\mathcal{M}$ be a nonstandard model of arithmetic and let $M$ be its universe. Let $U$ be a nonprincipal ultrafilter over $M$ and let $\mathcal{N}$ be the ultrapower $\mathcal{M}^M / U$. Let $F$ ...
2
votes
2answers
78 views

Are addition and multiplication on naturals algebraically distinguishable?

Suppose (N, +) and (N, *) are the structures of addition and multiplication on N, the natural numbers with 0. Let S be the set of equational identities that hold in (N, +), and let T be the set of ...
1
vote
2answers
63 views

Books/subjects for proof practice

So I want to practice writing proofs. I've studied general proof-writing but now I want to learn how to apply that to mathematics. From what I understand, the best and most accessible subjects for ...
4
votes
3answers
173 views

Where can I learn about Mathematical Philosophy?

This is a very vague question, but a question nonetheless. I am becoming increasingly more interested in what can be vaguely categorized as Mathematical Philosophy, or more specifically perhaps, ...
2
votes
2answers
102 views

Example of a proof using the axiom of commensurability

I'm teaching our intro to proofs course (well, one of them) and one of the classic illustrations of an overturned "axiom" is the Greek axiom of commensurability, which stated in geometric terms the ...
1
vote
1answer
104 views

Miller's Construction, Partition Principle and Failure of Axiom of Choice

Partition Principle ($PP$) is the following statement: For all sets $a$, $b$ there is an injection $f:a\rightarrow b$ iff there is a surjection $g:b\rightarrow a$ It is known that $ZF\vdash ...
1
vote
2answers
30 views

Logic with finite symbols

What obstructions do you run into if you're trying to develop first order logic when you only have finitely many constant, relation, and function symbols? Are there any cases where you actually need ...
2
votes
0answers
42 views

Propositions as sets of witnesses

Under the propositions-as-types paradigms, a proposition is identified with the type of all its proofs. From a more classical perspective (and assuming the full-blown axiom of choice), it sometimes ...
1
vote
2answers
41 views

Method of verifying answers

I have been reading Velleman's How to prove it book and solving problems of the exercise in it. What concerns me is that I cannot verify if actually my solutions are correct. The book has only ...
1
vote
0answers
58 views

Are there axiomatizations of first order logic or set theory defined in first order logic or set theory?

There are several axiomatizations for number theory, group theory, and other theories represented in first order logic. Further, these theories are also representable in set theory such as $\sf ZFC$ ...
0
votes
0answers
31 views

Most suitable book after Bergmann Logic Book

I'd like to know what the best book would be to pick up after this one would be. Essentially, it covers basic logical concepts (validity, soundness, consistency) and goes on to sentential and ...
1
vote
2answers
70 views

Universal quantifiers that are interpreted “almost-everywhere”

Often sentences that are false, are nonetheless "true almost everywhere." Example 0. The integers do not satisfy the cancellation law: $$\forall a\forall xy(ax = ay \rightarrow x=y)$$ This is ...
1
vote
0answers
94 views

A Question Regarding Consistent Fragments of Naive (Ideal) Set Theory

It is well known that Naive (to some, otherwise known as Ideal) set theory, that is, the set theory generated by the axioms: (EXT) (x)(x $\in$ A iff x $\in$ B) iff A=B (COMP) ($\exists$y)(x)(x ...
6
votes
0answers
53 views

Representation theorem for Heyting algebras?

A fundamental theorem by Stone asserts that any Boolean algebra is isomorphic to a subalgebra of the archetypical Boolean algebras, that is the power sets of a set $X$ (equipped with intersection, ...
3
votes
1answer
48 views

Introductions to classical and nonclassical logic?

I've found Eric Schechter: Classical and Nonclassical Logics: An Introduction to the Mathematics of Propositions a really nice book. But I'd like to skim through other books about the same subject, at ...
5
votes
1answer
75 views

Partial order on cardinalities without the axiom of choice

Cardinality can still be defined without choice, e.g. as equivalence class of equipotent sets, see Defining cardinality in the absence of choice. Injections define partial order on cardinalities by ...
4
votes
5answers
106 views

Book about different kind of logic

I'm searching for a book that talks about different kind of logic ( esoteric and particular one too ) and their uses and differences. Does such a book exist?
0
votes
2answers
67 views

Is this a good way to (or correct) proof?

Given: P ⇒ Q. To show: ¬Q ⇒ ¬P. Using modus tollens: Assume that ¬Q. Then ¬P. Thus ¬Q ⇒ ¬P. Does anybody have a good reference to how I can learn how to proof such formulas (including ...
1
vote
1answer
48 views

Best introduction to recursive functions

Hello I'm looking for a solid introduction to recursive functions within the domain of mathematical logic. I'm studying logic and would like to become more informed about this area of theory. I would ...
1
vote
1answer
84 views

Modal set-theory

In his “The Potential Hierarchy of Sets”, Review of Symbolic Logic 6:2 (2013), 205-28 Øystein Linnebo has proposed a modal set-theory. I was wondering what kind of utility can such a theory have for a ...
7
votes
2answers
279 views

Graduate level elementary logic books

I've done two courses on Logic during my Bachelor course, but they were very basic. Now I'm going to start by PhD, and I'm interested in learning "real Logic". Could you please provide some references ...
1
vote
1answer
36 views

Partial order version of elementary equivalence

Elementary equivalence is an important concept in mathematical logic. Two models $\mathfrak{M}$ and $\mathfrak{N}$ of the same signature are elementarily equivalent, written $\mathfrak{M} \equiv ...
4
votes
2answers
80 views

Graph that represents logical reasoning

The proof of a statement $X$ in terms of assumptions $A$, $B$ and $C$ can sometimes be represented using a directed graph: $$ \begin{matrix} & & X\\ & \nearrow & & ...
3
votes
2answers
83 views

Ultrafilter Lemma implies Compactness/Completeness of FOL

Apologies if this has been asked somewhere before, but I didn't see what I was looking for after several pages of Google results. I was reading Jech's The Axiom of Choice and was introduced to the ...
5
votes
2answers
121 views

Finite Model Theory

It seems that finite model theory is regarded (in a sense) as a computer theoretic subject. Is this the case or are there questions of interest that are of interest to mathematical logicians or more ...
5
votes
1answer
193 views

Asymmetric roles that are symmetric in every instance

This is similar to something else I posted, but this time we'll pretend we've never heard of infinite sets or infinite series. \begin{align} & \sin(\alpha+\beta+\gamma+\delta+\varepsilon+\zeta) ...
3
votes
1answer
131 views

Book recommendation in Foundational Mathematics

I have been navigating in this "foundational world" of mathematics for a while now ( but certainly not long enough and not deep enough ) and have read a bit about many different topics : set theory, ...
2
votes
2answers
150 views

Logic and number theory books

I've recently decided to start preparing for uni, so I figured I need to learn logic and some number theory. I picked up Burton's Elementary Number Theory and wasn't quite comfortable with it, seemed ...
1
vote
0answers
25 views

Basic questions about descriptive complexity

I'm trying to learn descriptive complexity, and I'm having trouble on a basic level wrapping my head around what it means for a logical formula to define a computational language. I've tried and ...
3
votes
2answers
122 views

Gödel's incompleteness theorems: where to learn? Is there a straightforward relation between the two?

What would be a good textbook or paper to learn the proofs of the two Gödel's incompleteness theorems from? I would prefer it to be as close to the original proofs as possible. I have not tried to ...
5
votes
2answers
146 views

Modern book on Gödel's incompleteness theorems in all technical details

Is there a modern book on Gödel's incompleteness theorems that goes into each and every technical aspect of the proof of them (a classical one, if such exists)? I'm not interested in popular ...
11
votes
2answers
232 views

Putting down axioms for some symbols. Playing with their consequences qualitatively and symbolically. Building theories. The book?

I am interested in the design and building of theories. By building theories, I mean putting down axioms of various kinds, over various fields, exploring their perhaps interesting, or probably boring, ...
3
votes
1answer
66 views

Intuitionistic Linear Logic

I am currently going through some papers that use the "intuitionistic version" of Girard's Linear Logic. Problem is, i seem to find very little literature on it. There is a lot done on Linear Logic ...
2
votes
2answers
112 views

I would like some textbook recommendations for model theory

I am a 3rd year undergraduate math student and would like to study model theory. . I have some background with set theory, ordinals etc and also with mathematical logic. This is purely for self study ...
1
vote
1answer
54 views

Suggestion for independent study of mathematical logic

Hello I'm looking for advice on mathematical logic books that are good for self-study. I would really like a text that has some if not all of the answers to exercises so I can check my progress as I ...
5
votes
2answers
205 views

Interaction of completeness and second incompleteness theorems

So I was reading the Wikipedia article on Godel's completeness theorem, the section on its relation to completeness. It says that completeness gives the existence of a model of arithmetic $\mathcal M ...
3
votes
0answers
50 views

Logic in closed symmetric monoidal categories; reference request.

Suppose we want an algebraic theory $T$ to be interpretable in any closed symmetric monoidal category $\mathbf{C}.$ I am thinking in particular of the case where $\mathbf{C}$ is the category of models ...
0
votes
1answer
54 views

Help with positive- and negative-forms in Proof Theory

I need help in understanding a device used bu Kurt Schütte, Proof Theory (1977). In treating classical sentential calculus, he use - in place of truth-tables - the device of positive- and ...
3
votes
3answers
135 views

Some reference for categorical logic?

By "categorical logic" I mean category-theoretical models of logic. In particular, I am more interested in models of intuitionistic predicate logic with conjunction, disjunction, implication and ...
3
votes
3answers
259 views

Online lectures for a first course in mathematical logic

I have a friend who is interested in learning math. I suggested that he learns mathematical logic. He has never learnt mathematical logic before, however I believe he has all the necessary ...
6
votes
5answers
199 views

The deep structure of logical formulas

A long-standing question to which I never found a concise answer is: Is there something like an unambiguous deep structure of a formula of propositional logic, opposed to its comparingly ...
12
votes
2answers
201 views

Founding Arithmetic on geometry

In the past I found some fleeting references that some (Frege in his later years being one of them) tried to found arithmetic not on set-theory and logic but on geometry and logic. Unfortunedly Frege ...
4
votes
1answer
124 views

Can one define $\langle x,y\rangle$ in $P(C)$?

I study at course Foundations of Mathematics the below definitions and lemma: $\langle x,y\rangle:=\{\{x\},\{x,y\}\}$ (from Kuratowski 1921) $\langle x,y\rangle:=\{\{\{x\},\varnothing\}\{\{y\}\}\}$ ...
2
votes
0answers
56 views

Certain sequents as inference rules

Fix a signature $\sigma.$ Then a coherent formula is a first-order formula built using only $\{\wedge,\vee,\top,\bot,\exists\}.$ See the link for more information. Furthermore, by a "special" ...
1
vote
1answer
192 views

Recommendation on a rigorous and deep introductory logic textbook

In this post, I don't mean any word by its somewhat "mathematical or logical" meaning but just "literally". It's been three years since I started "formal" mathematics, and now I'm familiar with set ...
0
votes
0answers
31 views

T-norms with arity 3

I'm working on some 3D vectors with fuzzy values, and I'd like to devise some operations on them. After my brief search, I haven't been able to find any existing work on t-norms with arity n>2. Is ...
7
votes
0answers
118 views

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

I'm in the middle of revising my freely available and much-downloaded introductory notes Gödel Without (Too Many) Tears. (They are a sort of cut down version of part of my Gödel book, and I'm ...
3
votes
1answer
231 views

Mathematical logic book with answers to exercises

I'm sure a question similar to mine has been asked before, but I am looking for a mathematical logic book with answers to the exercises. I am studying independently and although I have good logic ...
4
votes
3answers
231 views

Good textbook for learning Sequent Calculus

There are many modern text books teaching logic using Natural Deduction. There are no books teaching logic using the axiomatic method (see Good book for learning and practising axiomatic logic ) Now ...
2
votes
0answers
38 views

Books/papers on model theory in non-monotonic logic

I am working on a project whose object language is in non-monotonic logic. Since the project involves reasoning about the models, I am thinking of translating a non-monotonic problem into a ...