# November 2023 Fritz Fest: Celebrating a career in Operator Theory, Ordinary Differential Equations, Partial Differential Equations and Quantum Theory

A conference in honor of Fritz Gesztesy's 70th birthday.

## November 3, 2023

## Department of Mathematics, Baylor University

## Registration:

There is no registration fee but all participants should use the registration form on this page to register. **Room reservations available until October 24, 2023**

### Featured Speakers:

- Professor Roger Nichols (Univeristy of Tennessee at Chattanooga, USA)
- Title: On the Krein--von Neumann Extension of an Ordinary Differential Operator
- Abstract: Among all nonnegative self-adjoint extensions of a densely defined, closed, nonnegative Hilbert space operator, the Friedrichs and Krein--von Neumann extensions are extremal in the sense that they are, respectively, the largest and smallest (with respect to order between nonnegative self-adjoint operators) such extensions. We survey recent results on the characterization via boundary conditions of the Krein--von Neumann extension of a strictly positive ordinary differential operator. This survey includes results for singular second-order operators, regular 2n-th order operators, and specific examples (Bessel, Jacobi, and one-term operators).

- Professor Rudi Weikard (University of Alabama at Birmingham, USA)
- Title: Weyl-Titchmarsh theory for first-order systems with distributional coefficients.
- Abstract: We investigate the spectral theory for the system Ju’+qu=wf of ordinary differential equations where J is a constant invertible skew-hermitian matrix while q is a hermitian and w a non-negative matrix whose entries are distributions of order 0. This is the most general setting for such equations due to the limitations on defining products of distributions. A major obstacle is the fact that, in general, the unique continuation of solutions of the differential equation is not possible. In this talk we will pay particular attention to 2x2 system thereby extending what is known about the classical Sturm-Liouville equation.

### Local Organizing Committee:

- Andrei Martinez-Finkelshtein
- Dorina Mitrea
- Marius Mitrea

### Tentative Schedule:

- Location: Armstrong Browning Library, Lewis-Birkhead Lecture Hall
- 2:30 - Coffee and Refreshments
- 3:15 - 3:30 - Introductory Remarks
- 3:30 - 4:20 - Talk 1
- 4:30 - 5:30 - Talk 2

### Venue:

The Department of Mathematics is located on the third floor of the Sid Richardson Science Building (Paul L.

Foster Success Center) but talks are scheduled in the **Armstrong Browning Library**, **Lewis-Birkhead Lecture Hall**

Use the Campus Map to locate these buildings.

Baylor University lies in Waco, Texas on Interstate I-35 between Dallas/Fort Worth and Austin, Texas.

### Hotel Information:

Hotel Indigo Waco - Baylor

211 Clay Ave. Waco, TX

254-754-7000

**(link works best on a computer rather than a mobile device)**

**Room reservations available until October 24, 2023**

### Practical information:

**Wi-Fi connection:** By all means plan on using **eduroam** if you have it. If you don't have it, get it now if your institution is a member. Other possibilities exist but are far inferior and cumbersome to organize.

**Parking: **If you plan to park a car on campus during the conference, please use this link (and continue on the next page by clicking on "Are you a visitor?") to register as a visitor.

The visiting parking slots comprise the first 3 rows starting from the left when confronting the main entrance of Sid Richardson, the mathematics building (between 3rd and 4th street); they are marked in green. (Faculty and Staff parking slots are to the right of the visitor slots and marked in yellow.) See the following map:

Sponsored by the **Simons Foundation** and the **Department of Mathematics **of Baylor University.