I would like to write about a new paper ([AJ15]) which Franziska Jahnke and I have written and put on the arXiv. It’s called Henselianity in the language of rings. In it we investigate the relationship between the following four properties of a field :
(h) is henselian, i.e. admits a nontrivial henselian valuation,
(eh) is elementarily henselian, i.e. every is henselian,
(def) admits a definable nontrivial henselian valuation, and
(-def) admits a -definable nontrivial henselian valuation.
Continue reading Henselianity in the language of rings, with Franziska Jahnke
I can’t get enough of Terry Tao’s blog What’s New, he writes so much and so brilliantly. Anyway, I found two really nice old-ish posts about model theory:
- this which talks about completeness, compactness, zeroth-order logic, and Skolemisation;
- and this which talks about nonstandard analysis, notions of `elementary convergence’ and `elementary completion’, countable saturation, compactness and saturation re-written from an analytical point-of-view, and the Szemerédi regularity lemma (something I always want to know more about).
I don’t have time to write anything more now, but later I will get back to it.