Andreas Lietz
I am a Set Theorists, my main interests are Forcing, Forcing Axioms and Large Cardinals.
Currently, I am a postdoc at TU Wien, being part of the Set Theory group there.
Previously, I completed my PhD under Ralf Schindler at the university of Münster. You can find my thesis here.
What is Forcing Equivalence?
An algebraic perspective. July 29th, 2024
We give a characterization of when exactly two forcings are forcing equivalent. We also argue that dense embeddings should be renamed.
Properness After a Cohen Real
A weird equivalence of $\mathrm{CH}$. July 9th, 2024
We discuss how the properness of Cohen forcing at $\omega_1$, as defined in $V$ is affected by adding a Cohen real to $V$. It turns out that this forcing stays proper iff $\mathrm{CH}$ holds in $V$.
The Basics of Namba Forcing
A streamlined approach. March 22nd, 2024
We give a short proof of the basic facts about Namba forcing: It preserves stationary subsets of $\omega_1$ (in particular it does not collapse $\omega_1$) and if $\mathrm{CH}$ holds then it does not add reals. Along the way we also prove that Namba forcing is semiproper iff the cofinal Strong Chang Conjecture holds.
News!
Sacks Prize February 13, 2024
The Association for Symbolic Logic has awarded me the Sacks prize for the most outstanding doctoral dissertation in mathematical logic of 2023! You can find my thesis here. The other winner is Scott Mutchnik.
Don't Force With Complete Boolean Algebras!
Use complete Boolean orders instead. January 25th, 2024
Complete Boolean algebras can be an extremely useful tool for forcing. However, the notion of a cBa is backwards in the theory of forcing.
Andreas Lietz
I am a Set Theorist, my main interests are Forcing, Forcing Axioms and Large Cardinals.
Currently, I am a postdoc at TU Wien and part of the Set Theory group there. I work with Sandra Müller.
Previously, I completed my PhD under the supervision of Ralf Schindler at the university of Münster. You can find my thesis here.