On the Shafberg
St. Wolfgang, Austria
I am a postdoc at Stockholm University with a Sverker Lerheden Fellowship.
Previously, I completed my PhD at the University of Warwick under the supervision of Prof. James Robinson, working on Lp convergence of eigenfunction expansions for second-order linear differential operators in the plane.
I may be reached at: ryan.acosta.babb at math.su.se
I am mainly interested in Harmonic Analysis and PDE, especially questions of convergence of Fourier series and their relatives.
In one dimension, there is only one way to truncate a partial sum: count up to a certain N. For eigenfunctions labelled by pairs of indices, as is the case of the Fourier series on Z2, we may truncate in several ways. For example, do we count pairs of indices (n, m) with |n|,|m| ≤ N, or instead count them with n2 + m2 ≤ N? It is a curious fact that Lp convergence can be obtained in the former case (for all p) but 'never' the latter: it fails for all p ≠ 2!
After proving new convergence results for triangular domains, I am studying how this convergence might be established in more general regions as they are deformed by homeomorphisms. For a list of publications, see my Research page.
I am an Associate Editor of the American Mathematical Monthly.
I used to organise the Warwick Junior Analysis and Probability Seminar.