### Recent Writing

- The exact strength of the class forcing theorem
- A model of the generic Vopěnka principle in which the ordinals are not $\Delta_2$-Mahlo
- A model of second-order arithmetic with the choice scheme in which $\Pi^1_2$-dependent choice fails
- Computable processes which produce any desired output in the right nonstandard model
- Virtual large cardinals

### Mathoverflow Activity

- Comment by Victoria Gitman on Does Con(ZF + Reinhardt) really imply Con(ZFC + I0)?@Stefan For some reason, I cannot click on the link.Victoria Gitman
- Comment by Victoria Gitman on Cofinality of $j(\kappa)$ for a measurability embedding $j:V\to M$ with critical point $\kappa$@AsafKaragila I edited the question to make it clearer. Maybe I will ask your version as a follow-up if you don't ask it first :).Victoria Gitman
- Comment by Victoria Gitman on Cofinality of $j(\kappa)$ for a measurability embedding $j:V\to M$ with critical point $\kappa$@AsafKaragila I should have done a better job stating my question clearly. I wanted to know precisely what Yair answered: whether there are models where $\text{cf}(j(\kappa))$ is smaller than the size of $j(\kappa)$. Your interpretation of the question is very interesting as well, but I think much harder to answer.Victoria Gitman

- Comment by Victoria Gitman on Does Con(ZF + Reinhardt) really imply Con(ZFC + I0)?
### Cantor’s Attic

- StableAdded stable ordinals. New page==$f$-Stable Ordinals== An ordinal $\alpha$ is $f$''-stable'' for a function $f$ such that $\alpha\leq f(\alpha)$ iff $L_{\alpha}\preceq_{1}L_{f(\alpha)}$. For example: The smallest $\Pi_{0}^1$-Reflective ordinal is (+1)-stable. ==$\beta$-Stable Ordinals== An ordinal $\alpha$ is $\beta$''-stable'' for an ordinal $\beta$ such that $\alpha\leq\beta$ iff $L_{\alpha}\preceq_{1}L_{\beta}$. An ordinal $\alpha$ is ''stable'' iff $L_{\alpha}\preceq_{1}L_{\omega_{1}}$. The smallest stable […]Zetapology
- User talk:Ordnials← Older revision Revision as of 02:16, 24 August 2017 Line 1: Line 1: Hi! Zetapology speaking. I would love it if we could come into contact in order to get this website back on the rails. Hi! Zetapology speaking. I would love it if we could come into contact in order to get this website […]Zetapology
- User talk:OrdnialsCreated page with "Hi! Zetapology speaking. I would love it if we could come into contact in order to get this website back on the rails." New pageHi! Zetapology speaking. I would love it if we could come into contact in order to get this website back on the rails.Zetapology
- User:ZetapologyCreated page with "Hi! I'm 14, and I love set theory and model theory. I can't yet understand all cardinal concepts, but I at least understand indescribable cardinals, reflective cardinals, and..." New pageHi! I'm 14, and I love set theory and model theory. I can't yet understand all cardinal concepts, but I at least understand […]Zetapology
- IndescribableMostly finished the page. ← Older revision Revision as of 18:12, 23 August 2017 (One intermediate revision by the same user not shown)Line 1: Line 1: {{DISPLAYTITLE:Indescribable cardinal}} {{DISPLAYTITLE:Indescribable cardinal}} +A cardinal $\kappa$ is ''indescribable'' if it holds the reflection theorem up to a certain point. This is important to mathematics because of the concern for […]Zetapology

- Stable

# Monthly Archives: March 2013

## Tennenbaum’s Theorem

Gödel’s Incompleteness Theorems established two fundamental types of incompleteness phenomena in first-order arithmetic (and stronger theories). The First Incompleteness Theorem showed that no recursive axiomatization extending ${\rm PA}$ can decide all properties of natural numbers and the Second Incompleteness Theorem … Continue reading

Posted in logic.2013
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## Order amidst the chaos: exploring Julia sets and the Mandelbrot set

This is a project with Mariama Wilson.

Posted in student projects
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## The Second Incompleteness Theorem

There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory … Continue reading

Posted in logic.2013
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## The First Incompleteness Theorem

Some people are always critical of vague statements. I tend rather to be critical of precise statements; they are the only ones which can correctly be labeled ‘wrong’. –Raymond Smullyan At the dawn of the $20^{\text{th}}$-century formal mathematics flourished. In … Continue reading

Posted in logic.2013
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