# On Some New Infinitary Logics . . . and (their) Model Theory SLALM – Concepción, Chile 12/19

On Some New Infinitary Logics . . . and (their) Model Theory

(A lecture during the Latin American Symposium of Mathematical Logic, Concepción, Chile, December 2019.)

Abstract: The first logic (called $L^1_\kappa$ for $\kappa$ a singular strong limit cardinal) I will speak about was introduced by Saharon Shelah in 2012. The logic $L^1_\kappa$ has many properties that make it very well adapted to model theory, despite being stronger than$L_{\kappa,\omega}$. However, it also lacks a good syntactic definition.
With Väänänen, we introduced the second logic (called $L^{1,c}_\kappa$,) as a variant of $L^1\kappa$ with a transparent syntax and many of the strong properties of Shelah’s logic. The third logic (called Chain Logic), while not new (it is due to Karp), has been revisited recently by Dzamonja and Väänänen) also in relation to Shelah’s $L^1_\kappa$ and the Interpolation property.

I will provide a description of these three logics, with emphasis on their relevance to model theory.