The Fifteenth Workshop on
Numerical Ranges and Numerical Radii

 at Toyo University, Kawagoe Campus
June 21-24, 2019.

Click the photo to see a large size. Another photo.

Slides and abstracts, booklet.


This is one of the couple of the special workshops for the celebrated Toeplitz-Hausdorff Theorem. The year 2018 was the 100 anniversary of the celebrated Toeplitz-Hausdorff Theorem asserting the numerical range of an operator is always convex. There has been a lot of research activities on the topic after this fundamental result was established. The high level of research activities are due to the many connections of the subject to different pure and applied areas. The purpose of the workshop is to stimulate research and foster interaction of researchers interested in the subject. The informal workshop atmosphere will facilitate the exchange of ideas from different research areas and, hopefully, the participants will leave informed of the latest developments and newest ideas. One may visit the website WONRA to see some background about the subject and previous meetings, and also the Wiki page for the history of the workshop and related meetings on the subject. Furthermore, to celebrate the 100 anniversary of the Toplitz-Hausdorff Theorem. Another special workshop was held in Germany in summer of 2018, and the 2020 workshop following the usual schedule will take place in Coimbra in the summer of 2020.


This work is supported by JSPS KAKENHI Grant Number JP17K05285
 (Hiroyuki Osaka).



·         21, June: Registration at room 1205.

·         22~23, June: Registration at room 1205. Talks at 1206.

·         Campus map

Schedule, Title and Abstracts


·         Each talk has 30 min.

·         Computer and projector are available; prepare a pdf file with USB memory.



·         From Narita Airport
1. Narita Airport – (KEISEI Sky liner) – Nippori – (JR Yamanote line) –   
    Ikebukuro – (Tobu Tojo line) – Tsurugasima  (3,200 Yen, 2h20m)

·         From Haneda Airport
1. Haneda Airport – (Keikyu line) – Shinagawa – (JR Yamanote line) -
    Ikebukuro – (Tobu Tojo line) – Tsurugasima  (1,200 Yen, 1h40m)
2. Haneda Airport – (Bus)- Kawagoe Station – (Tobu Tojo line)- Tsurugashima
    (1,900Yen, 2h10m)

·         From Tokyo Station
1. Tokyo – (JR Yamanote line) –  Ikebukuro – (Tobu Tojo line) –
    Tsurugasima  (720 Yen, 1h15m)

     The conference place is located in 20 minutes from the ``Tsurugashima station’’
on foot.
For more detail is here.

Notice: If you book a fright before 10:00 (resp. 9:00) from Narita Airport (resp. Haneda Airport), it is better to stay another hotel at central Tokyo area or near the airport on the day before.


We recommend the following hotels.

·         City inn Tsurugashima 
* 13-3 Kamihiroya Tsurugashima-shi, Saitama 350-2203 Japan
* 5,500~6,900Yen/night single
* tel: +81 49-285-1711
* 20 minutes from the conference place on foot
* See Google map for details.

Travel Information

If you need an ``invitation letter’’, send an e-mail to Takeaki Yamazaki
      (t-yamazaki at
      VISA information is seen in the web page:

Confirmed participants

Kennedy Ayam Ekiah (University of Maroua, Cameroon)

Sheriff S. Bah (Newton Institute of Technology & Management, Gambia)

Natalia Bebiano (University of Coimbra, Portugal)

Ssesanga Brian (Gulu University, Uganda)

Mao-Ting Chien (Soochow University, Taiwan)

Didier Roger Chi Nche (University of Ngaundere, Cameroon)

Muneo Ch (Kanagawa University, Japan)

Kennett Dela Rosa (Drexel University, USA)

Nakacwa Faridah (Mpigi Vacational & techinical institute, Uganda)

Masayo Fujimura (National Defense Academy of Japan, Japan)

Shigeru Furuichi (Nihon University, Japan)

Ramesh Golla (IIT, India)

Osamu Hatori (Niigata University, Japan)

Fumio Hiai (Tohoku University, Japan)

Jinchuan Hou (Taiyuan University of Technology, China)

Masatoshi Ito (Maebashi Institute of Technology, Japan)

Ssenkaali Julius (Lugazi techinical & Engeneering College, Uganda)

Seung-Hyeok, Kye (Seoul National University, Korea)

Pan Shun Lau (University of Nevada Reno, USA)

Hosoo Lee (Jeju National University, Korea)

Chi-Kwong Li (Organizer, College of William and Mary, USA)

Yongdo Lim (Sungkyunkwan University, Korea)

Violet Munka Ngwang (University of Maroua, Cameroon)

Sang K. Mendy (Newton Institute of Technology & Management, Gambia)

Masaru Nagisa (Chiba University, Japan)

Bbaale Nicholas (Masaka Techinical & Business College, Uganda)

Michiya Mori (The University of Tokyo, Japan)

Hiroshi Nakazato (Organizer, Hirosaki University, Japan)

Hiromichi Ohno (Shinsyu University, Japan)

Hiroyuki Osaka (Organizer, Ritsumeikan University, Japan)

Edward Poon (Embry-Riddle University, USA)

Patrick Rault (University of Nebraska at Omaha, USA)

Xiaofei Qi (Shanxi University, China) 

Takashi Sano (Yamagata University, Japan)

Yuki Seo (Osaka Kyoiku University, Japan)

Nassiwa Esther Shammah (Buganda Royal Insitute, Uganda)

Moki Smith Beckley (University of Ngaundere, Cameroon)

Ilya Spitkovsky (New York University Abu Dhabi, UAE)

Byaruhanga Stephen (Ymca Comprehensive Institute Kampala, Uganda)

Raymond Nung-Sing Sze (The Hong Kong Polytechnic University, Hong Kong)

Hiroki Tamura (Yamagata University, Japan)

Ming-Cheng Tsai (Taipei University of Technology, Taiwan)

Shuhei Wada (National Institute of Technology, Kisarazu College, Japan)

An-Bao Xu (Wenzhou University, China)

Takeaki Yamazaki (Organizer, Toyo University, Japan)

Kenjiro Yanagi (Josai University, Japan)

Masahiro Yanagida (Tokyo University of Science, Japan)