## Seminars and Colloquia Schedule

Monday, March 12, 2018 - 14:00 , Location: Skiles 006 , Jim Belk , Bard College , Organizer: Dan Margalit
Monday, March 12, 2018 - 15:05 , Location: Skiles 005 , Michael Temkin , Hebrew University , Organizer: Matt Baker
The structure of non-archimedean curves X and their tame covers f:Y-->X is well understoodand can be adequately described in terms of a (simultaneous) semistable model. In particular, asindicated by the lifting theorem of Amini-Baker-Brugalle-Rabinoff, it encodes all combinatorialand residual algebra-geometric information about f. My talk will be mainly concerned with the morecomplicated case of wild covers, where new discrete invariants appear, with the different function being the most basic one. I will recall its basic properties following my joint work with Cohen and Trushin,and will then pass to the latest results proved jointly with U. Brezner: the different functioncan be refined to an invariant of a residual type, which is a (sort of) meromorphic differential form on the reduction, so that a lifting theorem in the style of ABBR holds for simplest wild covers.
Wednesday, March 14, 2018 - 13:55 , Location: Skiles 005 , , Brown University , , Organizer: Galyna Livshyts
We consider totally irregular measures $\mu$ in $\mathbb{R}^{n+1}$, that is, $$\limsup_{r\to0}\frac{\mu(B(x,r))}{(2r)^n} >0 \;\; \& \;\; \liminf_{r\to0}\frac{\mu(B(x,r))}{(2r)^n}=0$$for $\mu$ almost every $x$. We will show that if $T_\mu f(x)=\int K(x,y)\,f(y)\,d\mu(y)$ is an operator whose kernel $K(\cdot,\cdot)$ is the gradient of the fundamental solution for a uniformly elliptic operator in divergence form associated with a matrix with H\"older continuous coefficients, then $T_\mu$ is not bounded in $L^2(\mu)$.This extends a celebrated result proved previously by Eiderman, Nazarov and Volberg for the $n$-dimensional Riesz transform and is part of the program to clarify the connection between rectifiability of sets/measures on $\mathbb{R}^{n+1}$ and boundedness of singular integrals there. Based on joint work with Mihalis Mourgoglou and Xavier Tolsa.
Wednesday, March 14, 2018 - 13:55 , Location: Skiles 006 , Sarah Davis , GaTech , Organizer: Anubhav Mukherjee
Thursday, March 15, 2018 - 15:05 , Location: Skiles 006 , , University of Minnesota , , Organizer: Michael Damron