| Professor Hartmut Fuhr, RWTH Aachen University, Germany | 143 | Professor Hartmut Fuhr, RWTH Aachen University, Germany | Zoom | <p>​​Attend this seminar via <a href="https://udel.zoom.us/j/94746991367?pwd=L3BUczhnNENWN05paUxjODRLazZpQT09">Zoom​</a>. ​<br></p><p><strong>Title:</strong> Coarse geometric methods for generalized wavelet approximation theory<br><br><strong>Abstract:</strong>
Generalized wavelet systems in higher dimensions arise from the action
of suitable semidirect products $\mathbb{R}^d \rtimes H$ on ${\rm
L}^2(\mathbb{R}^d)$. Here $H$ denotes a suitably chosen matrix group
acting on functions by dilations. The approximation theoretic
properties of these systems are coded in the associated {\em coorbit
spaces}, defined by imposing suitably weighted $L^p$-norms on the
transform side. Understanding the dependence of the scale of coorbit
spaces on the dilation group is one of the basic problems of the theory,
and generally not well understood.<br><br>The talk translates this
question into a problem from the domain of coarse geometry. Under
suitable technical assumptions on two dilation groups $H_1,H_2$, the
dual action of these groups induces a map $\varphi: H_1 \to H_2$, and
it can be shown that $H_1$ and $H_2$ have the same scale of coorbit
spaces if and only if $\varphi$ is a quasi-isometry with respect to word
metrics defined on $H_1$Â and $H_2$.<br><br> As an application of
this method, we present a classification result for so-called
generalized shearlet dilation groups in arbitrary dimensions.<br><br>(Based on joint work with Rene Koch.)​<br></p> | 11/16/2021 8:30:00 PM | 11/16/2021 9:30:00 PM | | |
| Professor Elias Katsoulis, East Carolina University | 142 | Professor Elias Katsoulis, East Carolina University | In-person talk at EWG 336 | <p>​<b>Title: </b>The isomorphism problem for tensor algebras of C*-correspondences.<br><br><b>Abstract: </b>The tensor algebras of C*-correspondences include as motivating examples the semicrossed products, the graph algebras and various other algebras. In this talk we will be concerned with the isomorphism problem between such algebras. We will review some old work and present some recent developments obtained jointly with Chris Ramsey.<br></p> | 10/26/2021 7:30:00 PM | 10/26/2021 8:30:00 PM | | |
| Dr. Yemon Choi, Lancaster University, UK | 141 | Dr. Yemon Choi, Lancaster University, UK | Zoom | <p>​​Attend this seminar via <a href="https://udel.zoom.us/j/94746991367?pwd=L3BUczhnNENWN05paUxjODRLazZpQT09">Zoom​</a>. ​<br></p><p><span class="wrap-text"><strong>Title:</strong> Operator space tensor products, and cocycles on Fourier algebras<br><br><strong>Abstract:</strong> When
studying Fourier algebras of locally compact groups, it is commonly
accepted that we need to use the projective tensor product of operator
spaces. On the other hand, the study of derivations on Fourier algebras
has revealed a potentially rich area for investigation, but such
derivations can never be completely bounded, and hence there would seem
to be no reason why they should interact well with operator space tensor
products.<br><br>In this talk I will explain more about these two
themes, and why they presented an obstacle until recently when trying to
construct non-trivial 2-cocycles on Fourier algebras. I will then
outline how the obstacle can be overcome by making use of extra
structure for certain derivations, together with a "twisted inclusion"
result for operator space tensor products.</span><br></p> | 10/19/2021 7:30:00 PM | 10/19/2021 8:30:00 PM | | |
| Professor Qiyu Sun, University of Central Florida | 140 | Professor Qiyu Sun, University of Central Florida | Zoom | <b>Title: </b>Polynomial filters of multiple commutative shifts and their distributed implementation<br><br><b>Abstract: </b>Graph signal processing provides an innovative framework to handle data residing on distributed networks. Polynomial graph filters and their inverses play important roles in graph signal processing. The concept of commutative graph shifts plays a similar role in graph signal processing as the one-order delay in classical multi-dimensional signal processing. In this talk, we consider the filtering and inverse filtering procedure associated polynomial filters of multiple commutative shifts. We also consider iterative approximation algorithms and the associated distributed optimization problems.​​<br><br><p>Attend this seminar via <a href="https://udel.zoom.us/j/94746991367?pwd=L3BUczhnNENWN05paUxjODRLazZpQT09">Zoom​</a>. <br></p> | 10/5/2021 7:30:00 PM | 10/5/2021 8:30:00 PM | | |
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