### Boole’s Rings

- On conjugacy problems for graphs and trees October 11, 2019 Samuel Coskey
- (with Y. Hayut) Perfect Subtree Property for Weakly Compact Cardinals October 10, 2019 Sandra Müller
- Structural properties of the stable core October 10, 2019 Victoria Gitman
- Ground model definability in ${\rm ZF}$ October 10, 2019 Victoria Gitman
- (with S.-D. Friedman and V. Gitman) Structural Properties of the Stable Core October 4, 2019 Sandra Müller

### Comments on Boole’s Rings

- Comment on Solution to my transfinite epistemic logic puzzle, Cheryl’s Rational Gifts by Cheryl’s Rational Gifts: transfinite epistemic logic puzzle challenge! | Joel David Hamkins October 14, 2019 Comments for Joel David Hamkins
- Comment on The propagation of error in classical geometry constructions by Paul Alberti-Strait October 9, 2019 Comments for Joel David Hamkins
- Comment on The modal logic of arithmetic potentialism and the universal algorithm by The $Sigma_1$-definable universal finite sequence | Joel David Hamkins September 30, 2019 Comments for Joel David Hamkins
- Comment on I know that you know that I know that you know…. Oxford, October 2019 by Joel David Hamkins September 25, 2019 Comments for Joel David Hamkins
- Comment on I know that you know that I know that you know…. Oxford, October 2019 by charlie sitler September 25, 2019 Comments for Joel David Hamkins

# Category Archives: Results worth knowing

## An example with Dedekind cuts

In this post, I will briefly describe an example in computability theory that is well known, but not easy to find in the literature. It gives one reason why Dedekind cuts are difficult to work with computationally. Theorem. There is … Continue reading

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## Filter quantifiers

I have been supervising an undergraduate student in an independent study in topology this semester. We have just finished the Stone–Čech compactification, and the semester is ending, so I want to end with an ultrafilter based proof of Hindman’s theorem. … Continue reading

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## Computable roots of computable functions

Here are several interesting results from computable analysis: Theorem 1. If $f$ is a computable function from $\mathbb{R}$ to $\mathbb{R}$ and $\alpha$ is an isolated root of $f$, then $\alpha$ is computable. Corollary 2. If $p(x)$ is a polynomial over … Continue reading