## Contact Info

Pure MathematicsUniversity of Waterloo

200 University Avenue West

Waterloo, Ontario, Canada

N2L 3G1

Departmental office: MC 5304

Phone: 519 888 4567 x43484

Fax: 519 725 0160

Email: puremath@uwaterloo.ca

Tuesday, May 14, 2019 — 2:00 PM EDT

**Robert Xu Yang, Department of Pure Mathematics, University of Waterloo**

"Sidon and Kronecker-like sets in harmonic analysis"

Let $G$ be a compact abelian group and $\Gamma$ be its discrete dual group. In this thesis we study various types of interpolation sets.

A subset $E \subset \Gamma$ is Sidon if every bounded function on $E$ can be interpolated by the Fourier transform of a finite complex measure. Sidon sets have been extensively studied, and one significant breakthrough, that Sidonicity is equivalent to proportional quasi-independence, was proved by Bourgain and Pisier during the early 80s. In this thesis we will give a detailed demonstration of Pisier's approach. We also seek for possible extensions of Pisier's theorems. Based on Pisier's techniques, we will show Sidonicity is equivalent to proportional independence of higher degrees and minimal constants.

A subset $E \subset \Gamma$ is $\epsilon$-Kronecker if every function on $E$ with range in the unit circle can be interpolated by a continuous character on $\Gamma$ with an error of $\epsilon$. We will prove some interesting properties of $\epsilon$-Kronecker sets and give an estimation of the Sidon constant of such sets. Generalizations of Kronecker sets include binary Kronecker sets and $N$-pseudo-Rademacher sets. We compute the binary Kronecker constants of some interesting examples. For $N$-pseudo-Rademacher sets, we give a characterization of such sets, describe their structures and prove the existence of large $N$-pseudo-Rademacher sets.

MC 5403

University of Waterloo

200 University Avenue West

Waterloo, Ontario, Canada

N2L 3G1

Departmental office: MC 5304

Phone: 519 888 4567 x43484

Fax: 519 725 0160

Email: puremath@uwaterloo.ca

University of Waterloo

University of Waterloo

43.471468

-80.544205

200 University Avenue West

Waterloo,
ON,
Canada
N2L 3G1

The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land granted to the Six Nations that includes six miles on each side of the Grand River. Our active work toward reconciliation takes place across our campuses through research, learning, teaching, and community building, and is centralized within our Indigenous Initiatives Office.