(See past events)

### Colloquium

Keri Kornelson, Oklahoma.

Friday, September 21 at 4:00pm in Ritter 231 with refreshments beforehand in the Ritter Hall Lobby.

**Norm retrieval via spatiotemporal samples**

Abstract: There is a relaxation of the problem of phase retrieval in which the magnitude of a signal is computed from phaseless measurements. We require less information, so can be possible with fewer measurements than phase retrieval. As a ready example, an orthonormal basis yields norm retrieval measurements. In this talk, we introduce the concepts and earlier results about performing phase and norm retrieval in real, finite-dimensional space. We then present recent work with Fatma Bozkurt in which we do norm retrieval with dynamical samples, i.e. samples obtained at selected measurement points but repeated over time.

### Statistics Seminar

Tim Keller, Saint Louis U.

Thursday, September 27 at 3:00pm in Ritter 204

**Stratified Simple Random Sampling with Multiple Estimation Objectives**

Abstract: Non-response is the greatest challenge facing establishment surveys. A major contributing factor for survey non-response is respondent burden. To meet this challenge survey establishments must therefore strive to meet estimation goals with the smallest possible sample size.

A common and basic survey design is the stratified simple random sample, and a common estimate of interest is the population total for a survey item. For this special case, the problem of meeting multiple estimation objectives is formulated as a convex optimization problem, and a numerical method for determining the optimal allocation of a fixed overall sample size is presented.

### Colloquium

Elodie Pozzi, Saint Louis U.

Friday, October 5 at 4:00pm in Ritter 231 with refreshments beforehand in the Ritter Hall Lobby.

**A 2D inverse problem in magnetism**

### Colloquium Schedule

The Math/Stat Colloquium this semester will meet at 4:00pm in RH 231 with refreshments beforehand at 3:30 in the Ritter Lobby.

Our current schedule:

- Friday, September 7, Haiyan Cai, UMSL (Analysis)
- Friday, September 21, Keri Kornelson, Oklahoma Univ. (Analysis)
- Friday, October 5, Elodie Pozzi, Saint Louis University
- Friday, October 19, Ken Jacobs, Northeastern Univ. (Algebra)
- Friday, November 2, Chris Connell, Indiana Univ. (Topology)
- Wednesday, November 14, Shmuel Wienberger, Univ. of Chicago (Topology)