I am an Assistant Professor at the Research Center for Pure and Applied Mathematics at Tohoku University.


My main research interests are in algebraic combinatorics and number theory. I am particularly interested in spectral graph theory and algebraic integers whose conjugates are geometrically constrained.

Papers and preprints

Listed in order of completion.
[11] (with Soicher) On the clique number of a strongly regular graph.
[10] (with Mohar and O) Interlacing families and the Hermitian spectral norm of digraphs.
[9] (with Suda) Symmetric and skew-symmetric $\{0,\pm 1\}$-matrices with large determinants.
[8] (with Cheng and Koolen) Graphs with three eigenvalues and second largest eigenvalue at most 1.
[7] (with Cheng, Gavrilyuk, and Koolen) Biregular graphs with three eigenvalues. European J. Combin. 56 (2016), pp. 57–80.
[6] (with Koolen, Munemasa, and Szöllősi) Equiangular lines in Euclidean spaces. J. Combin. Theory Ser. A 138 (2016), pp. 208–235.
[5] (with Koolen, Munemasa, Sano, and Taniguchi) Edge-signed graphs with smallest eigenvalue greater than -2. J. Combin. Theory Ser. B 110 (2015), pp. 90–111.
[4] Small-span Hermitian matrices over quadratic integer rings. Math. Comp. 84 (2015), no. 291, pp. 409–424.
[3] (with Taylor) Lehmer’s conjecture for Hermitian matrices over the Eisenstein and Gaussian integers. Electron. J. Combin. 20 (2013), no. 1, #P42.
[2] Cyclotomic matrices over real quadratic integer rings. Linear Algebra Appl. 437 (2012), no. 9, pp. 2252–2261.
[1] Cyclotomic matrices over the Eisenstein and Gaussian integers. J. Algebra 372 (2012), pp. 560–583.

Curriculum Vitae and PhD thesis

Get a copy of my CV and my PhD thesis, Cyclotomic Matrices over Quadratic Integer Rings.


Here is a list of some conferences and research visits.


1. The Japanese Conference on Combinatorics and its Applications (JCCA 2016)
from 21st May 2016 until 25th May 2016
Kyoto University, Kyoto, Japan

from 9th May 2016 until 13th May 2016
KIAS, Seoul, South Korea

3. Queen Mary, University of London
from 3rd March 2016 until 4th March 2016
Queen Mary, University of London, London, UK

4. Royal Holloway, University of London
from 1st March 2016 until 2nd March 2016
Royal Holloway, University of London, Egham, UK

5. Korea-Japan Workshop on Algebra and Combinatorics
from 28th January 2016 until 30th January 2016
Pusan National University, Pusan, Korea

6. Hiroshima University
from 28th November 2015 until 29th November 2015
Hiroshima University, Hiroshima, Japan

7. The Fourth Workshop on Spectral Graph Theory and Related Topics
from 20th November 2015 until 22nd November 2015
University of Tsukuba, Tsukuba, Japan

8. Binghamton University
from 17th October 2015 until 23rd October 2015
Binghamton University, Vestal, New York, US

9. University of Waterloo
from 9th October 2015 until 17th October 2015
University of Waterloo, Waterloo, Ontario, Canada

10. The Geometry, Algebra and Analysis of Algebraic Numbers
from 4th October 2015 until 9th October 2015
Banff International Research Station, Canada

11. Simon Fraser University
from 28th September 2015 until 2nd October 2015
Simon Fraser University, Burnaby, British Columbia, Canada

12. International Workshop on Algebraic Combinatorics
from 18th September 2015 until 23rd September 2015
Zhejiang University, China

13. Systems of Lines: Applications of Algebraic Combinatorics
from 10th August 2015 until 14th August 2015
Worcester Polytechnic Institute, Worcester, Massachusetts, US

14. CoCoA 2015 - Combinatorics and Computer Algebra
from 19th July 2015 until 25th July 2015
Colorado State University, Fort Collins, Colorado, US

15. 8th Slovenian Conference on Graph Theory
from 21st June 2015 until 29th June 2015
Kranjska Gora, Slovenia

16. Workshop on Algebraic Combinatorics
from 17th June 2015 until 18th June 2015
Tilburg University, The Netherlands

17. The Third Workshop on Spectral Graph Theory and Related Topics
from 13th March 2015 until 15th March 2015
Hiroshima Institute of Technology, Hiroshima, Japan

18. Japan-Korea Workshop on Algebra and Combinatorics
from 29th January 2015 until 31st January 2015
Kyushu Institute of Technology, Fukuoka, Japan

19. Research on Finite Groups and Their Representations, Vertex Operator Algebras, and Algebraic Combinatorics
from 16th December 2014 until 19th December 2014
Research Institute for Mathematical Sciences, Kyoto University, Japan

20. Algebraic Combinatorics Workshop
from 26th November 2014 until 29th November 2014
University of Science and Technology of China, China

21. The Japanese Conference on Combinatorics and its Applications
from 25th August 2014 until 29th August 2014
University of Tsukuba, Tsukuba City, Japan

22. Seoul ICM 2014
from 13th August 2014 until 21st August 2014
Coex, Seoul, South Korea

23. ICM2014 Satellite Conference on Extremal and Structural Graph Theory
from 5th August 2014 until 9th August 2014
Gyeongju, South Korea

24. Algebraic Combinatorics: Spectral Graph Theory, Erdös-Ko-Rado Theorems and Quantum Information Theory
from 23rd June 2014 until 27th June 2014
University of Waterloo, Canada

25. Modern Trends in Algebraic Graph Theory
from 2nd June 2014 until 5th June 2014
Villanova, Pennsylvania, US

26. Japan Conference on Graph Theory and Combinatorics
from 17th May 2014 until 21st May 2014
Nihon University, Tokyo, Japan

27. Pusan National University
from 26th January 2014 until 28th January 2014
Pusan National University, Busan, South Korea

28. Korea-Japan workshop on algebra and combinatorics
from 23rd January 2014 until 25th January 2014
KAIST, Daejeon, South Korea

29. The Second Workshop on Spectral Graph Theory and Related Topics
from 29th November 2013 until 30th November 2013
Mathematical Institute, Tohoku University, Sendai, Japan

30. Workshop on Algebraic Combinatorics
from 17th November 2013 until 21st July 2013
Hebei Normal University, Hebei, China

31. A Conference in Celebration of Peter Cameron
from 8th July 2013 until 10th July 2013
Queen Mary, University of London, UK

32. 24th British Combinatorial Conference:
from 30th June 2013 until 5th July 2013
Royal Holloway, University of London, UK

33. 第30回代数的組合せ論シンポジウム
from 24th June 2013 until 26th June 2013
Shizuoka University, Japan

34. Workshop on Algebraic Combinatorics
from 7th March 2013 until 7th March 2013
Kobegakuin University, Kobe, Japan

35. The First Workshop on Algebraic Graph Theory, Spectral Graph Theory and Related Topics
from 5th January 2013 until 6th January 2013
Nagoya University, Nagoya, Japan

Last updated: 21st June 2016