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Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

1 vote
Accepted

Resource request (probability theory, computability theory, algebra)

Here are a few areas of overlap for those research topics. Computable model theory is a nice overlap of computability theory and algebra, since one is looking at the nature of computably effective pr …
Joel David Hamkins's user avatar
24 votes
Accepted

Which recursively-defined predicates can be expressed in Presburger Arithmetic?

Presburger arithmetic admits elimination of quantifiers, if one expands the language to include truncated minus and the unary relations for divisibility-by-2, divisibility-by-3 and so on, which are de …
Martin Sleziak's user avatar
18 votes

Are there mutually independent undecidable statements?

Here is an easy way to see it. Let $A$ assert that if PA is inconsistent, the smallest $k$ for which $\Sigma_k$ induction is inconsistent is a multiple of $3$. Let $B$ make the similar assertion tha …
Joel David Hamkins's user avatar
10 votes

Are there applications of category theory to countable sets?

Allow me to reinterpret your question as the inquiry How can abstract infinitary constructions inform us about the finite? To my mind, this is the troubling or at least surprising possibility at the …
Martin Sleziak's user avatar
31 votes

Are the two meanings of "undecidable" related?

To my way of thinking, the two notions of undecidability are closely related, and the associated undecidability phenomenon and independence phenomenon, which are both pervasive in mathematics, are dee …
Joel David Hamkins's user avatar
67 votes

Knuth's intuition that Goldbach might be unprovable

You are right to view the Goldbach conjecture as having a particularly simple logical form. Such statements of the form "for every $n$, property $P(n)$ holds", where $P$ is a particularly simple state …
Martin Sleziak's user avatar
21 votes

Siegel zeros and other "illusory worlds": building theories around hypotheses believed to be...

I believe that there are many instances of this phenomenon in set theory, where an elaborate theory is developed over a period of years by many people, even though the theory is not viewed ultimately …
Joel David Hamkins's user avatar
26 votes

Siegel zeros and other "illusory worlds": building theories around hypotheses believed to be...

I have heard that Jack Silver's discovery of zero sharp ($0^\#$) was part of his attempt to show measurable cardinals inconsistent. Instead of finding the long-sought-after contradiction, however, he …
Joel David Hamkins's user avatar
35 votes

How do we recognize an integer inside the rationals?

The integers can indeed be defined in the rational field, but not in the real field. $\newcommand\Q{\mathbb{Q}}\newcommand\Z{\mathbb{Z}}\newcommand\R{\mathbb{R}}$ The question can be made precise by i …
Joel David Hamkins's user avatar
9 votes
Accepted

A notion of thinness for subsets of $\omega$, using chromatic number

The two notions are incomparable. To see that the first notion does not imply the second, let's construct a set $S$ with asymptotic density $0$, but with infinite chromatic number. We place infinitely …
Joel David Hamkins's user avatar
19 votes
3 answers
1k views

The arithmetic progression game and its variations: can you find optimal play?

Consider the arithmetic progression game, a two-player game of perfect information, in which the players take turns playing natural numbers, or finite sets of natural numbers, all distinct, and the fi …
6 votes

Set of rational numbers generated by some rules

To start things off, here is a simple observation: the set $S$ is contained in the rational interval $\mathbb{Q}\cap[\frac 12,1]$, the rational numbers $\frac ab$ where $0<a\leq b\leq 2a$. The reaso …
Joel David Hamkins's user avatar
3 votes

What kind of arithmetic information does the ring of integers in an infinite extension carry?

Picking up on the phrase "arithmetic information" in your question, let me give a brief answer coming from logic, although I recognize that this is likely not the answer for which you are looking. L …
Joel David Hamkins's user avatar
61 votes
Accepted

If I exchange infinitely many digits of $\pi$ and $e$, are the two resulting numbers transce...

Nice question, Erin. Here is one quick easy thing to say. If $\pi$ and $e$ disagree in infinitely many digits, then there are continuum many choices of the particular subset of those digits to swap, …
Joel David Hamkins's user avatar
40 votes
Accepted

Has decidability got something to do with primes?

Goedel did indeed use the Chinese remainder theorem in his proof of the Incompleteness theorem. This was used in what you describe as the `boring' part of the proof, the arithmetization of syntax. Con …
Gerry Myerson's user avatar

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