# Dr Yemon Choi

Lecturer in Pure Mathematics## Research Interests

See https://www.maths.lancs.ac.uk/~choiy1/pubmath/papers.html for my papers.

### The keyword version

Banach and operator algebras. Noncommutative harmonic analysis. Categorical and homological perspectives on functional analysis.

### The longer version

I am interested in a range of topics and problems on the interface between algebra and functional analysis. This tends to be driven by particular families of examples, but my preference is for finding general frameworks that unify common features of these examples, once one has investigated individual examples in depth.

In recent years I have worked intensively on various aspects of the Fourier algebras of locally compact groups: studying these objects involves a blend of (non-commutative) harmonic analysis and representation theory. Many of the developments over the last 20 years or so use the tools, or are guided by the philosophy, of the theory of *operator spaces* and *completely bounded maps* -- these may be thought of as enriched versions of Banach spaces and linear maps between them, where one allows matricial coefficients and not just scalar ones.

I am also interested in algebras of convolution operators arising from the canonical representation(s) of a group G on the Banach space L^{p}(G). When *p*=2 there is a rich theory available, from the world of C*-algebras and von Neumann algebras; for other values of *p* many basic structural questions remain unresolved, even for very explicit examples such as G=SL_{n}(R) or SL_{n}(Z).

## Web Links

http://www.maths.lancs.ac.uk/~choiy1/

## Professional Role

Director of Studies for Study Abroad students

## PhD Supervisions Completed

Mahmood Alaghmandan, 2013. (Supervised at the University of Saskatchewan, Canada, joint with E. Samei)

Bence Horvath, 2019. (Joint with N. J. Laustsen)

Christopher Menez, 2019.

## Career Details

Jan. 2014 - present: Lecturer at Lancaster University, United Kingdom

Aug. 2010 - Jan. 2014: Assistant Professor (tenure-track), University of Saskatchewan, Canada

Aug. 2008 - Jul. 2010: Postdoctoral researcher, Universite Laval, Canada

Feb. 2007 - Jul. 2008: Postdoctoral fellow, University of Manitoba, Canada

Sept. 2002 - Jun. 2006: PhD student, University of Newcastle upon Tyne, United Kingdom

Sept. 2001 - Jun, 2002: Editorial assistant, National Extension College, United Kingdom.

## Qualifications

B.A. in Mathematics (2000, Cambridge).

CASM (2001, Cambridge).

PhD in Pure Mathematics (2006, Newcastle-upon-Tyne)

## PhDs Examined

External examiner

S. Trotter (Leeds, PhD, 2016)

Y. Ji (Newcastle, PhD, 2018)

Internal examiner

E. Kastis (PhD, Lancaster, 2017)

## PhD Supervision Interests

#### Availability

I would be interested in taking new PhD students for a 2021-22 start. I am keen to hear from applicants with a strong background in functional analysis. Some previous exposure to representation theory of groups or the general theory of (matrix) Lie groups would be desirable.

#### Current ideas for PhD projects

Here are three possible areas in which I am willing to supervise: each of these is not a specific PhD project, but a setting in which there are various possible research problems that a student could work on. If you would like to know more, then please feel free to get in touch.

- Algebras associated to group actions on L
^{p}spaces - Cohomological invariants of Fourier algebras
- Properties of Banach-Kähler modules

#### Warning notes.

Themes 1 and 2 are likely to require some prior exposure to the basic theory of C*-algebras. However, some of the necessary background can be learned in the initial stages of the PhD, and depending on the individual strengths of an applicant there may be particular projects that require less functional-analytic machinery; some questions may be suitable for those with solid basic analysis and interests in the representation theory of finite groups.

It is possible that you are reading this and have had some exposure to various structural properties of Banach algebras known as "approximate amenability", "character amenability", or "module amenability". **I will not, for the foreseeable future, supervise on any of these three, nor on any hybrid of these.**

LMS- Dr. Ebrahim Samei -Collaboration

01/01/1900 → …

Research

Fourier algebras and dual convolution

Invited talk

An introduction to non-amenability of B(E)

Invited talk

Amenability constants of centres of group algebras

Invited talk

Constructing alternating cocycles on Fourier algebras

Invited talk

Alternating cocycles on Fourier algebras of Lie groups

Invited talk

Approximate homomorphisms: some old and new results

Invited talk

British Mathematical Colloquium

Participation in conference

Jon Bannon

Hosting an academic visitor

Twisted tensor products, and cocycles on Fourier algebras

Invited talk

Some results on direct finiteness of group algebras

Invited talk

CAP and ITAP for group von Neumann algebras

Invited talk

Derivations on semigroup algebras and Fourier algebras

Invited talk

Unitarizable group representations and amenable operator algebras

Invited talk

Weak amenability of Fourier algebras: old and new results

Invited talk

Analysis and Probability

Analysis and Probability

- Analysis and Probability