The presentations cover a large variety of topics and are intended for a general math audience. The seminar is organized by Prof. Eduardo Gonzalez and we usually meet Wednesdays afternoons, from 2:30 p.m. to 4 p.m.
UMass Boston Mathematics seminar. Science 2-064. Sept 28.
Speaker: Vanja Dunjko.
Title: Perturbative renormalization group and Padé approximation
Abstract: In the single-variable case, perturbative renormalization group
requires no special symmetries and is thus a purely formal method for improving
convergence properties of series expansions. In fact, up to a series reversion,
it is a type of integral Hermite-Padé approximation. It is especially useful
for interpolating between expansions for small values of a variable and a
scaling law of known exponent for large values. As an example, we extract the
scaling-law prefactor for the one-body density matrix of the Lieb-Liniger gas.
Using a recent result for the 4th-order term in the short-distance expansion, we
find a remarkable agreement with known ab initio numerical results.