### Boole’s Rings

- A countable ordinal definable set of reals without ordinal definable elements January 20, 2017 Victoria Gitman
- Regula Krapf, Ph.D. 2017, University of Bonn January 12, 2017 Joel David Hamkins
- Set-theoretic geology and the downward directed grounds hypothesis, Bonn, January 2017 January 10, 2017 Joel David Hamkins
- My Mathematics Genealogy January 4, 2017 Dana C. Ernst
- Transfinite game values in infinite chess, including new progress, Bonn, January 2017 January 3, 2017 Joel David Hamkins

### Comments on Boole’s Rings

- Comment on A countable ordinal definable set of reals without ordinal definable elements by Victoria Gitman January 21, 2017 Comments for Victoria Gitman
- Comment on A countable ordinal definable set of reals without ordinal definable elements by Robert Solovay January 20, 2017 Comments for Victoria Gitman
- Comment on There are no nondegenerate regular polygons in the integer lattice, except for squares by Joel David Hamkins January 17, 2017 Comments for Joel David Hamkins
- Comment on There are no nondegenerate regular polygons in the integer lattice, except for squares by Pierre B. January 17, 2017 Comments for Joel David Hamkins
- Comment on Math for nine-year-olds: fold, punch and cut for symmetry! by Fold Your Way to Glory – Study Score Calc January 14, 2017 Comments for Joel David Hamkins

# Monthly Archives: January 2012

## An incompleteness theorem for β_{n} models

My first paper was “An incompleteness theorem for $\beta_n$ models” with Stephen Simpson [1]. It’s a short paper, but the idea is very pretty. We know that the incompleteness theorem implies there are strange models of arithmetic, but these models … Continue reading

Posted in Papers, Research
2 Comments

## AMS/ASL Special Session on Alan Turing

I arrived home yesterday from the 2012 Joint Mathematics Meetings in Boston, where I was a co-organizer of the AMS/ASL Special Session on the Life and Legacy of Alan Turing. The talks were wonderful, and the session went very smoothly, … Continue reading

Posted in Meetings
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