# Dr. Bertrand Teguia Tabuguia, Ph.D.

## A mathematics lover!

### Introduction

I recently completed my Ph.D. in Mathematics, in the field of Computer Algebra at the University of Kassel, some details are given below. I have obtained a master's degree in Mathematics at the African Institute for Mathematical Sciences (AIMS) - Cameroon in 2018, and another in Computer Engineering at Ecole Nationale Supérieure Polytechnique (ENSP) de Yaoundé in 2016.

I am currently working as a researcher at the University of Kassel to continue some work arising from my Ph.D.

Address: University of Kassel, Germany. Heinrich-Plett-Str.40. 34132 Kassel

Email:  bteguia@mathematik.uni-kassel.de / bertrand.teguia@aims-cameroon.org

Alternative web page: http://www.mathematik.uni-kassel.de/~bteguia/

Tel:  +49 1521 2117745 / +237 676915434

### Power Series Representations of Hypergeometric Type and Non-Holonomic Functions in Computer Algebra

Ph.D. (Dr. rer. nat.) in Mathematics, Computer Algebra, from August 2018 - Mai 2020, University of Kassel, Germany.

I worked under the supervision of Prof. Dr. Wolfram Koepf

I give below brief details of my major results.

1. An algorithm, say mfoldHyper, that computes bases of the subspaces of all m-fold (m being a positive integer) hypergeometric term solutions of holonomic recurrence equations. This algorithm is new, and it has the advantage to linearize the computation of Laurent-Puiseux series: every linear combination of hypergeometric type series, even for many different values of m, is detected.

2. An algorithm that computes normal form representations for non-holonomic functions. A very important consequence of this algorithm is its ability to prove difficult identities.

3. A variant of van Hoeij's algorithm for computing hypergeometric term solutions of holonomic recurrence equations. Following the main steps of van Hoeij's algorithm, our variant computes hypergeometric term solutions of holonomic recurrence equations as fast as the original algorithm while using other methods. This algorithm is an integral part of mfoldHyper mentioned in 1.. Download this algorithm here (latest update: 01/10/2020).

PS: papers related to these achievements will soon be available.

The thesis is available at meine Dissertation.

### Maxima implementations

Maxima is a free computer algebra system (CAS). I use it for most of my symbolic computations. In particular, Maxima was the CAS used during my Ph.D. work.

The pictures present some outputs obtained with my Ph.D. algorithms.

My package FPS.mac is available by email request.

Power series computed thanks to mfoldHyper

Non-trivial zero equivalence identified

### Where am I from?

I got a master's degree in computer engineering at Ecole Nationale Superieure Polytechnique (ENSP) de Yaoundé, Cameroon. When I was a student in that school, I was always doing my best to stay close to mathematics. I have then been introduced to Computer Algebra in level 4 for a pre-engineering internship, and I did my master thesis in advanced statistics where I wrote an algorithm for forests dynamic. My stay with pure mathematics books and friends made me known as a pure mathematician computer engineer, and from my mathematician lecturers, I had enough support to go to AIMS-Cameroon where I could pursue my dream. I indeed performed well at AIMS and got my Ph.D. opportunity...