CURRENT POSITION / CONTACT INFO

Panayiotis J. Psarrakos, Professor (Linear Algebra)
Laboratory of Algebraic, Geometrical and Topological Applications (Director of the Laboratory, 7/2021 - present)
Department of Mathematics (Head of the Department, 1/2013 - 10/2015)
School of Applied Mathematical and Physical Sciences (Dean of the School, 9/2016 - 8/2018)
National Technical University of Athens (Vice Rector of the University, for administrative and student affairs, 11/2023 - present)
Zografou Campus, 15780
Athens, GREECE
Office 3.11, Building E
Office hours:   Tuesday 10:30-12:00,   Wednesday 12:30-14:00
Tel.:  30 210 772 1697
E-mail:  ppsarr "at" math "dot" ntua "dot" gr

 TEACHING COURSES (2023-2024, NATIONAL TECHNICAL UNIVERSITY OF ATHENS)

 Fall semester

Linear Algebra and Analytic Geometry, School of Mechanical Engineering.
Linear Algebra, School of Electrical and Computer Engineering.
Linear Algebra and Analytic Geometry, School of Rural, Surveying and Geoinformatics Engineering.

 Spring semester

Linear Algebra and its Applications, School of Applied Mathematical and Physical Sciences.
Linear Algebra, School of Chemical Engineering.
Matrix Analysis and its Applications, School of Applied Mathematical and Physical Sciences.
Postgraduate Matrix Analysis, School of Applied Mathematical and Physical Sciences.

 EDUCATION

Ph.D., Mathematics, National Technical University of Athens, Greece, 1997.
B.Sc., Mathematics, University of Athens, Greece, 1991.

 SCHOLARSHIPS

12/94 - 12/97  Competed and awarded I.K.Y. (State Scholarships Foundation) grant for
                        doctoral dissertation.
8/94 - 12/94    Papakyriakopoulos scholarship as postgraduate student.
9/90 - 6/91      I.K.Y. (State Scholarships Foundation) scholarship as undergraduate student.

 RESEARCH INTERESTS        

Numerical range (field of values) of matrices and matrix polynomials (theory and numerics).
Spectral inclusion sets (envelope, Gershgorin-type sets) of matrices and matrix polynomials.
Spectral analysis and canonical forms of matrix polynomials (theory and numerics).
Eigenvalue perturbation theory, stability and pseudospectra (theory and numerics).
Analysis of nonnegative matrices and Perron-Frobenius theory.
Approximate Birkhoff-James orthogonality in normed linear spaces.
Hilbert spaces and indefinite inner product spaces.

 WORK EXPERIENCE

3/15 - present   Professor, National Technical University of Athens, Greece.
1/10 - 2/15      Associate Professor, National Technical University of Athens, Greece.
6/04 - 12/09    Assistant Professor, National Technical University of Athens, Greece.
2/01 - 5/04      Visiting Lecturer, National Technical University of Athens, Greece.
10/00 - 6/04    Visiting Lecturer, Technological Educational Institute of Halkida, Creece.
1/00 - 8/00      Post-Doctoral Fellow, University of Regina, Canada.
8/99 - 12/99    Post-Doctoral Fellow, University of Calgary, Canada.
1/98 - 7/99      Research Associate, National Technical University of Athens, Greece.
7/98 - 8/98      Research Visitor, University of Regina, Canada.
9/94 - 12/97    Teaching/Research Assistant, National Technical University of Athens, Greece.

 TEACHING IN NATIONAL TECHNICAL UNIVERSITY OF ATHENS (since 2001)

 Undergraduate courses

Linear Algebra and Analytic Geometry (School of Civil Engineering, School of Mechanical
Engineering, School of Electrical and Computer Engineering, School of Naval Architecture
and Marine Engineering, School of Applied Mathematical and Physical Sciences).
Linear Algebra and its Applications (School of Applied Mathematical and Physical Sciences).
Matrix Analysis and its Applications (School of Applied Mathematical and Physical Sciences).
Mathematical Analysis I (School of Rural and Surveying Engineering, School of Mining and
Metallurgical Engineering, School of Applied Mathematical and Physical Sciences).
Mathematical Analysis II (School of Electrical and Computer Engineering, School of
Chemical Engineering).

 Postgraduate course

Matrix Analysis (School of Applied Mathematical and Physical Sciences).

 SUPERVISION (Ph.D., M.Sc.)

Michael Rokidis (current Ph.D. student, M.Sc. 2011).
Christina Michailidou (current Ph.D. student, M.Sc. 2011).
Vasiliki Panagakou (Ph.D. 2021).
Christos Chorianopoulos (Ph.D. 2011, M.Sc. 2007).
Nikolaos Papathanasiou (Ph.D. 2009, M.Sc. 2005).
Nikolaos Matsavelas (M.Sc. 2021).
Eleftherios Moutzourellis (M.Sc. 2021).
Antonia Apostolaki (M.Sc. 2019).
Stefanos Theodorakopoulos (M.Sc. 2019).
Matoula Chasapi (M.Sc. 2018).
Evaggelia Gropa (M.Sc. 2017).
Aggeliki Kalara (M.Sc. 2016).
Christina-Georgia Makri (M.Sc. 2016).
Marianna Kouneli (M.Sc. 2010).
Stefanos Samaras (M.Sc. 2009).

 PERSONAL ACADEMIC SEARCH LINKS

Scholar Google, papers and citations.
Zentralblatt MATH, papers and citations.

 EDITORSHIP

   


Associate Editor (10/10 - present), Electronic Journal of Linear Algebra.
Associate Managing Editor (10/10 - 12/20), Electronic Journal of Linear Algebra.
Assistant Managing Editor (8/07 - 9/10), Electronic Journal of Linear Algebra.


     


Guest Editor, Linear Algebra and its Applications.
Special Issue for the 18th Conference of the International Linear Algebra Society, Rhode Island (6/2013).


     


Guest Editor, Journal of Applied Mathematics.
Special Issue on Advances in Matrices, Finite and Infinite, with Applications, 2014.
Special Issue on Advances in Matrices, Finite and Infinite, with Applications, 2013.

 REFEREEING

Linear Algebra and its Applications.
Electronic Journal of Linear Algebra.
SIAM Journal on Matrix Analysis and Applications.
Linear and Multilinear Algebra.
Operators and Matrices.
Numerical Linear Algebra with Applications.
Journal of Mathematical Analysis and Applications.
Integral Equations and Operator Theory.
Operator Theory: Advances and Applications.
Applied Mathematics Letters.
Applied Mathematics and Computation.
Mathematical and Computer Modelling.
Numerical Algorithms.
ACM Transactions on Mathematical Software.
IMA Journal of Mathematical Control and Information.
Central European Journal of Mathematics.
Journal of Optimization Theory and Applications.
Filomat.

 PUBLICATIONS

 Refereed journal publications (published or accepted)

1. Morad Ahmadnasab and Panayiotis J. Psarrakos.
    Homotopic deviation theory for regular matrix pencils.
    Linear and Multilinear Algebra, to appear (2024).


2. Morad Ahmadnasab and Panayiotis J. Psarrakos.
    Eigenvalue characterization of some structured matrix pencils under linear perturbation.
    Electronic Journal of Linear Algebra, v. 40 (2024), pp. 274-298.


3. Christos Chorianopoulos and Panayiotis Psarrakos.
    On the shell and the shell-extremal eigenvalues of a square matrix.
    Linear Algebra and its Applications, v. 665 (2023), pp. 354-381.


4. Georgios Katsouleas, Vasiliki Panagakou and Panayiotis Psarrakos.
    A note on the boundary of the Birkhoff-James epsilon-orthogonality sets.
    Electronic Journal of Linear Algebra, v. 38 (2022), pp. 32-48.


5. Vasiliki Panagakou, Panayiotis Psarrakos and Nikos Yannakakis.
    A Birkhoff-James cosine function for normed linear spaces.
    Aequationes Mathematicae, v. 95 (2021), pp. 889-914.


6. Thomas R. Cameron and Panayiotis J. Psarrakos.
    On Householder sets for matrix polynomials.
    Linear Algebra and its Applications, v. 585 (2020), pp. 105-126.


7. Thomas R. Cameron and Panayiotis J. Psarrakos.
    On Descarte's rule of signs for matrix polynomials.
    Operators and Matrices, v. 13 (2019), pp. 643-652.


8. Christina Michailidou and Panayiotis Psarrakos.
    Gershgorin type sets for eigenvalues of matrix polynomials.
    Electronic Journal of Linear Algebra, v. 34 (2018), pp. 652-674.


9. Esmaeil Kokabifar, Panayiotis Psarrakos and Ghasem Barid Loghmani.
    On the distane from a matrix polynomial to matrix polynomials with
    some presribed eigenvalues.
    Linear Algebra and its Applications, v. 544 (2018), pp. 158-185.


10. Aikaterini Aretaki, Panayiotis Psarrakos and Michael Tsatsomeros.
     The envelope of tridiagonal Toeplitz matrices and block-shift matrices.
     Linear Algebra and its Applications, v. 532 (2017), pp. 60-85.


11. Vasiliki Panagakou, Panayiotis Psarrakos and Nikos Yannakakis.
     Birkhoff-James epsilon-orthogonality sets of vectors and vector-valued
     polynomials.
     Journal of Mathematical Analysis and Applications, v. 454 (2017), pp. 59-78.


12. E. Kokabifar, G.B. Loghmani, P.J. Psarrakos and S.M. Karbassi.
     On the distance from a matrix polynomial to matrix polynomials
     with k prescribed distinct eigenvalues.
     Linear and Multilinear Algebra, v. 65 (2017), pp. 658-676.


13. E. Kokabifar, G.B. Loghmani and P.J. Psarrakos.
     On the distance from a weakly normal matrix polynomial to
     matrix polynomials with a prescribed multiple eigenvalue.
     Electronic Journal of Linear Algebra, v. 31 (2016), pp. 71-86.


14. Panayiotis Psarrakos and Michael Tsatsomeros.
     On the geometry of the envelope of a matrix.
     Applied Mathematics and Computation, v. 244 (2014), pp. 132-141.


15. Christos Chorianopoulos and Panayiotis Psarrakos.
     On the continuity of Birkhoff-James epsilon-orthogonality sets.
     Linear and Multilinear Algebra, v. 61 (2013), pp. 1447-1454.


16. Panayiotis Psarrakos.
     Distance bounds for prescribed multiple eigenvalues of matrix polynomials.
     Linear Algebra and its Applications, v. 436 (2012), pp. 4107-4119.


17. Panayiotis Psarrakos and Michael Tsatsomeros.
     An envelope for the spectrum of a matrix.
     Central European Journal of Mathematics, v. 10 (2012), pp. 292-302.

18. Christos Chorianopoulos and Panayiotis Psarrakos.
     Birkhoff-James approximate orthogonality sets and numerical ranges.
     Linear Algebra and its Applications, v. 434 (2011), pp. 2089-2108.


19. Christos Chorianopoulos, Panayiotis Psarrakos and Frank Uhlig.
     A method for the inverse numerical range problem.
     Electronic Journal of Linear Algebra, v. 20 (2010), pp. 198-206.

20. Nikolaos Papathanasiou and Panayiotis Psarrakos.
     On condition numbers of polynomial eigenvalue problems.
     Applied Mathematics and Computation, v. 216 (2010), pp. 1194-1205.


21. Christos Chorianopoulos, Sotirios Karanasios and Panayiotis Psarrakos.
     A definition of numerical range of rectangular matrices.
     Linear and Multilinear Algebra, v. 57 (2009), pp. 459-475.


22. Stavros Fatouros and Panayiotis Psarrakos.
     An improved grid method for the computation of the pseudospectra
     of matrix polynomials.
     Mathematical and Computer Modelling, v. 49 (2009), pp. 55-65.


23. Nikolaos Papathanasiou and Panayiotis Psarrakos.
     Normal matrix polynomials with nonsingular leading coefficients.
     Electronic Journal of Linear Algebra, v. 17 (2008), pp. 458-472.

24. Nikolaos Papathanasiou and Panayiotis Psarrakos.
     The distance from a matrix polynomial to matrix polynomials with
     a prescribed multiple eigenvalue.
     Linear Algebra and its Applications, v. 429 (2008), pp. 1453-1477.


25. Lyonell Boulton, Peter Lancaster and Panayiotis Psarrakos.
     On pseudospectra of matrix polynomials and their boundaries.
     Mathematics of Computation, v. 77 (2008), pp. 313-334.


26. Panayiotis Psarrakos.
     A distance bound for pseudospectra of matrix polynomials.
     Applied Mathematics Letters, v. 20 (2007), pp. 499-504.

27. Panayiotis Psarrakos and Michael Tsatsomeros.
     Bounds for Levinger's function of nonnegative almost
     skew-symmetric matrices.
     Linear Algebra and its Applications, v. 416 (2006), pp. 759-772.

28. Mao-Ting Chien, Hiroshi Nakazato and Panayiotis Psarrakos.
     The q-numerical range and the Davis-Wielandt shell of reducible
     3-by-3 matrices.
     Linear and Multilinear Algebra, v. 54 (2006), pp. 79-112.

29. Gregory Kalogeropoulos and Panayiotis Psarrakos.
     The polar decomposition of block companion matrices.
     Computers & Mathematics with Applications, v. 50 (2005), pp. 529-537.

30. Peter Lancaster and Panayiotis Psarrakos.
     On the pseudospectra of matrix polynomials.
     SIAM J. Matrix Anal. Appl., v. 27 (2005), pp. 115-129.

31. Mao-Ting Chien, Hiroshi Nakazato and Panayiotis Psarrakos.
     On the q-numerical range of matrices and matrix polynomials.
     Linear and Multilinear Algebra, v. 53 (2005), pp. 357-374.

32. Gregory Kalogeropoulos and Panayiotis Psarrakos.
     On the solution of homogeneous matrix difference equations.
     J. Inst. Math. Comput. Sci. Math. Ser., v. 18 (2005), pp. 51-58.

33. Panayiotis Psarrakos and Charalampos Tsitouras.
     Numerical approximation of the boundary of numerical range of
     matrix polynomials.
     Appl. Numer. Anal. & Comput. Math., v. 2 (2005), pp. 126-133.

34. Gregory Kalogeropoulos and Panayiotis Psarrakos.
     A note on the controllability of higher order dynamical systems.
     Applied Mathematics Letters, v. 17 (2004), pp. 1375-1380.

35. Panayiotis Psarrakos and Michael Tsatsomeros.
     A primer of Perron-Frobenius theory for matrix polynomials.
     Linear Algebra and its Applications, v. 393 (2004), pp. 333-351.

36. Gregory Kalogeropoulos, Panayiotis Psarrakos and Nickos Karcanias.
     On the computation of the Jordan canonical form of regular matrix polynomials.
     Linear Algebra and its Applications, v. 385 (2004), pp. 117-130.

37. Panayiotis Psarrakos.
     On the estimation of the q-numerical range of monic matrix polynomials.
     Electronic Transactions on Numerical Analysis, v. 17 (2004), pp. 1-10.

38. Maria Adam and Panayiotis Psarrakos.
     On a compression of normal matrix polynomials.
     Linear and Multilinear Algebra, v. 52 (2004), pp. 251-263.

39. Judith McDonald, Panayiotis Psarrakos and Michael Tsatsomeros.
     Almost skew- symmetric matrices.
     Rocky Mountain Journal of Mathematics, v. 34 (2004), pp. 269-288.

40. Panayiotis Psarrakos.
     Definite triples of Hermitian matrices and matrix polynomials.
     Journal of Computational and Applied Mathematics, v. 151 (2003), pp. 39-58.

41. Panayiotis Psarrakos and Michael Tsatsomeros.
     The Perron eigenspace of irreducible nonnegative almost skew-symmetric
     matrices and Levinger's transformation.
     Linear Algebra and its Applications, v. 360 (2003), pp. 43-57.

42. Panayiotis Psarrakos.
     On the m-th roots of a complex matrix.
     Electronic Journal of Linear Algebra, v. 9 (2002), pp. 32-41.

43. Panayiotis Psarrakos and Michael Tsatsomeros.
     On the stability radius of matrix polynomials.
     Linear and Multilinear Algebra, v. 50 (2002), pp. 151-165.

44. Maria Adam, John Maroulas and Panayiotis Psarrakos.
     Numerical range of rational matrix functions.
     Linear and Multilinear Algebra, v. 50 (2002), pp. 75-89.

45. Peter Lancaster, Alexander Markus and Panayiotis Psarrakos.
     Repeated eigenvectors and the numerical range of self-adjoint
     quadratic operator polynomials.
     Integral Equations and Operator Theory, v. 44 (2002), pp. 243-253.

46. John Maroulas, Panayiotis Psarrakos and Michael Tsatsomeros.
     Perron-Frobenius type results on the numerical range.
     Linear Algebra and its Applications, v. 348 (2002), pp. 49-62.

47. Mao-Ting Chien, Hiroshi Nakazato and Panayiotis Psarrakos.
     Point equation of the boundary of numerical range of a matrix polynomial.
     Linear Algebra and its Applications, v. 347 (2002), pp. 205-217.

48. Douglas Farenick and Panayiotis Psarrakos.
     A triangle inequality in Hilbert modules over matrix algebras.
     Linear Algebra and its Applications, v. 341 (2002), pp. 57-67.

49. Peter Lancaster and Panayiotis Psarrakos.
     The numerical range of selfadjoint quadratic matrix polynomials.
     SIAM J. Matrix Anal. Appl., v. 23 (2001), pp. 615-631.

50. Panayiotis Psarrakos.
     A note on the level sets of a matrix polynomial and its numerical range.
     Operator Theory: Advances and Applications, v. 130 (2001), pp. 277-281.

51. Hiroshi Nakazato and Panayiotis Psarrakos.
     On the shape of numerical range of matrix polynomials.
     Linear Algebra and its Applications, v. 338 (2001), pp. 105-123.

52. Peter Lancaster and Panayiotis Psarrakos.
     Normal and seminormal eigenvalues of analytic matrix functions.
     Integral Equations and Operator Theory, v. 41 (2001), pp. 331-342.

53. Steve Kirkland, Panayiotis Psarrakos and Michael Tsatsomeros.
     On the location of the spectrum of hypertournament matrices.
     Linear Algebra and its Applications, v. 323 (2001), pp. 37-49.

54. Panayiotis Psarrakos.
     The q-numerical range of matrix polynomials, II.
     Bulletin of Greek Mathematical Society, v. 45 (2001), pp. 3-15.

55. Panayiotis Psarrakos.
     Numerical range of linear pencils.
     Linear Algebra and its Applications, v. 317 (2000), pp. 127-142.

56. Panayiotis Psarrakos and Panayiotis Vlamos.
     The q-numerical range of matrix polynomials.
     Linear and Multilinear Algebra, v. 47 (2000), pp. 1-10.

57. John Maroulas, Panayiotis Psarrakos and Michael Tsatsomeros.
     Separable characteristic polynomials of pencils and property L.
     Electronic Journal of Linear Algebra, v. 7 (2000), pp. 182-190.

58. Panayiotis Psarrakos and Michael Tsatsomeros.
     On the relation between the numerical range and the joint
     numerical range of matrix polynomials.
     Electronic Journal of Linear Algebra, v. 6 (2000), pp. 20-30.

59. John Maroulas and Panayiotis Psarrakos.
     On factorization of matrix polynomials.
     Linear Algebra and its Applications, v. 304 (2000), pp. 131-139.

60. John Maroulas and Panayiotis Psarrakos.
     Numerical range of matrix polynomials.
     Bulletin of Greek Mathematical Society, v. 42 (1999), pp. 59-83.

61. Alexander Markus, John Maroulas and Panayiotis Psarrakos.
     Spectral properties of a matrix polynomial connected with a
     component of its numerical range.
     Operator Theory: Advances and Applications, v. 106 (1998), pp. 305-308.

62. John Maroulas and Panayiotis Psarrakos.
     On the connectedness of numerical range of matrix polynomials.
     Linear Algebra and its Applications, v. 280 (1998), pp. 97-108.


63. John Maroulas and Panayiotis Psarrakos.
     A connection between numerical ranges of selfadjoint matrix polynomials.
     Linear and Multilinear Algebra, v. 44 (1998), pp. 327-340.


64. John Maroulas and Panayiotis Psarrakos.
     The boundary of numerical range of matrix polynomials.
     Linear Algebra and its Applications, v. 267 (1997), pp. 101-111.


65. John Maroulas and Panayiotis Psarrakos.
     Geometrical properties of numerical range of matrix polynomials.
     Computers & Mathematics with Applications, v. 31 (1996), pp. 41-47.

 Refereed monographic series publications (published or accepted)

1. Miltiadis Karamanlis and Panayiotis J. Psarrakos.
    Birkhoff-James epsilon-orthogonality sets in normed linear spaces.
    Textos de Matematica, University of Coimbra, v. 44 (2013), pp. 81-92.

Numerical Ranges of Matrix Polynomials and Applications (in Greek).
National Technical University of Athens, December 1997.
Supervisor: Professor John Maroulas.

 Books

Panayiotis Psarrakos.
Introduction to Linear Algebra (in Greek, 585+x pages).
Tsotras Publications, Athens, 2021.


Panayiotis Psarrakos, Efstratios Rappos and Panayiotis Vlamos.
Number Theory (in Greek, 264+xi pages).
Publications of Greek Mathematical Society, Athens, 2000.

 Lecture Notes

Panayiotis J. Psarrakos.
Topics in Matrix Analysis (in Greek, 155+vi pages).
National Technical University of Athens, 2020 (first edition 2014).

Peter Lancaster and Panayiotis Psarrakos.
A note on weak and strong linearizations of regular matrix polynomials.
Numerical Analysis Report no. 470, Manchester Centre for Computational Mathematics,
University of Manchester, 2005.

Panayiotis Psarrakos and Michael Tsatsomeros.
Numerical range: (in) a matrix nutshell, Parts 1 / 2.
Mathematical Notes from Washington State University, v. 45 (2002) / v. 46 (2003).

Panayiotis J. Psarrakos.
Factorization of matrix polynomials (in Greek).
Mathimatiki Epitheorisi of Greek Mathematical Society, v. 55 (2001), pp. 112-126.

A. Economou, P. Psarrakos, E. Rappos, P. Vlamos and E. Vlamou.
Partitions of integer numbers in international mathematical olympiads (in Greek).
Mathimatiki Epitheorisi of Greek Mathematical Society, v. 51 (1999), pp. 113-129.

1. 10-th Seminar on Linear Algebra and its Applications (online meeting).
    Shahid Bahonar University, Kerman, Iran (8/2020).
    Title: From matrices to matrix polynomials.


2. 19-th Conference of the International Linear Algebra Society (photo 1, photo 2).
    Sungkyunkwan University, Seoul, Korea (8/2014).
    Title: Travelling from matrices to matrix polynomials.


3. 2012 Haifa Matrix Theory Conference (photo).
    Technion-Israel Institute of Technology, Haifa, Israel (11/2012).
    Title: Birkhoff-James epsilon-orthogonality sets and numerical ranges.


4. Workshop on Linear Algebra and its Applications to Financial Engineering (photo).
    Institute for Financial and Actuarial Mathematics, University of Liverpool, U.K. (1/2012).
    Title: Distance bounds for prescribed multiple eigenvalues of matrix polynomials.


5. Workshop on Pseudospectra and Structural Dynamics.
    Laboratory for Advanced Dynamic Engineering, University of Bristol, U.K. (12/2004).
    Title: On pseudospectra of matrix polynomials.

 Contributed talks

1. 25-th Conference of the International Linear Algebra Society (photo 1, photo 2, photo 3).
    Politecnica de Madrid, Madrid, Spain (6/2023).
    Title: An envelope for the spectrum of a square matrix.

2. IWOTA 2022, International Workshop on Operator Theory and Applications (photo).
    Krakow, Poland (9/2022).
    Title: Birkhoff-James epsilon-orthogonality sets in normed linear spaces.


3. NASCA 2018, Numerical Analysis and Scientific Computation with Applications (photo 1, photo 2).
    Kalamata, Greece (7/2018).
    Title: Gershgorin type sets for polynomial eigenvalue problems.


4. FCGM 2018, First Congress of Greek Mathematicians.
    Hellenic Mathematical Society, University of Athens, Athens, Greece (6/2018).
    Title: Gershgorin type sets for polynomial eigenvalue problems.

5. 14-th Workshop on Numerical Ranges and Numerical Radii (photo).
    Technical University of Munich, Munich, Germany (6/2018).
    Title: Birkhoff-James epsilon-orthogonality sets of vectors and vector-valued polynomials.

6. 20-th Conference of the International Linear Algebra Society (photo).
    KU Leuven, Leuven, Belgium (7/2016).
    Title: An envelope for the spectrum of a matrix.

7. 13-th Workshop on Numerical Ranges and Numerical Radii (photo).
    Soochow University, Taipei, Taiwan (6/2016).
    Title: Birkhoff-James approximate orthogonality sets.

8. MASSEE International Congress on Mathematics, Athens, Greece (9/2015).
    Title: Birkhoff-James approximate orthogonality sets.

9. ACA 2015, Applications of Computer Algebra, Kalamata, Greece (7/2015).
    Title: Travelling from matrices to matrix polynomials.


10. 25-th International Workshop on Operator Theory and its Applications, Tbilisi, Georgia (7/2015).
     Title: Birkhoff-James approximate orthogonality sets.

11. 18-th Conference of the International Linear Algebra Society (photo).
     University of Rhode Island, Providence, U.S.A. (6/2013).
     Title: On the spectrum envelope of a matrix.

12. NumAn 2012, Conference in Numerical Analysis, Recent Approaches to Numerical Analysis:
     Theory, Methods and Applications. University of Ioannina, Greece (9/2012).
     Title: An envelope for the spectrum of a matrix.

13. 2012 SIAM Conference on Applied Linear Algebra (photo).
     Universitat Politecnica de Valencia, Spain (6/2012).
     Title: Applications of SVD to perturbation theory of eigenvalues of matrix polynomials.

14. NumAn 2010, Conference in Numerical Analysis, Recent Approaches to Numerical Analysis:
     Theory, Methods and Applications (photo 1, photo 2). Chania, Greece (9/2010).
     Title: A simple algorithm for an inverse numerical range problem.

15. 16-th Conference of the International Linear Algebra Society (photo).
     University of Pisa, Italy (6/2010).
     Title: The distance from a matrix polynomial to a prescribed multiple eigenvalue.

16. Applied Linear Algebra (ALA 2010) - In honor of Hans Schneider (photo 1, photo 2).
     University of Novi Sad, Serbia (5/2010).
     Title: A numerical range of rectangular matrices and matrix polynomials.

17. NumAn 2008, Conference in Numerical Analysis, Recent Approaches to Numerical Analysis:
     Theory, Methods and Applications. Kalamata, Greece (9/2008).
     Title: On the numerical estimation of pseudospectra of matrix polynomials.

18. 19-th International Workshop on Operator Theory and its Applications.
    College of William and Mary, Williamsburg, Virginia, U.S.A. (7/2008).
     Title: Normal matrix polynomials.

19. 9-th Workshop on Numerical Ranges and Numerical Radii (photo).
     College of William and Mary, Williamsburg, Virginia, U.S.A. (7/2008).
     Title: A definition of numerical range based on the Birkhoff-James orthogonality.

20. 8-th Panhellenic Conference in Algebra and Number Theory.
     National Technical University of Athens, Greece (5/2008).
     Title: Normal matrix polynomials.

21. 12-th Panhellenic Conference in Mathematical Analysis.
     University of Athens, Greece (5/2008).
     Title: Pseudospectra of matrix polynomials and their boundaries.

22. NumAn 2007, Conference in Numerical Analysis, Recent Approaches to Numerical Analysis:
     Theory, Methods and Applications. Kalamata, Greece (9/2007).
     Title: The distance to matrix polynomials with a prescribed multiple eigenvalue.

23. Joint GAMM-SIAM Conference on Applied Linear Algebra.
     University of Dusseldorf, Germany (7/2006).
     Title: Pseudospectra of matrix polynomials and their boundaries.

24. 13-th Conference of the International Linear Algebra Society.
     Vrije University of Amsterdam, Netherlands (7/2006).
     Title: Bounds for Levinger's function of nonnegative almost skew-symmetric matrices.

25. 10-th Panhellenic Conference in Mathematical Analysis.
     National Technical University of Athens, Greece (10/2004).
     Title: Pseudospectra of polynomial eigenvalue problems.

26. International Conference of Numerical Analysis and Applied Mathematics 2004.
     Technological Educational Institute of Halkida, Greece (9/2004).
     Title: Numerical approximation of the boundary of numerical range of matrix polynomials.

27. 11-th Conference of the International Linear Algebra Society (photo).
     University of Coimbra, Portugal (7/2004).
     Title: On the pseudospectra of matrix polynomials.

28. 7-th Workshop on Numerical Ranges and Numerical Radii.
     University of Coimbra, Portugal (7/2004).
     Title: Numerical approximation of the numerical range of matrix polynomials.

29. International Conference of Influence of Traditional Mathematics and
     Mechanics on Modern Science and Technology. Messini, Greece (5/2004).
     Title: On the Jordan canonical form of matrix polynomials.

30. International Conference in Recent Advances in Statistical Design
     and Related Combinatorics.
     University of Athens, Greece (7/2003).
     Title: On the location of the spectrum of generalized tournament matrices.

31. 9-th Panhellenic Conference in Mathematical Analysis.
     Technical University of Crete, Chania, Greece (9/2002).
     Title: On the Jordan canonical form of regular matrix polynomials.

32. 4-th Panhellenic Conference in Algebra and Number Theory.
     University of Patras, Greece (5/2002).
     Title: On the m-th roots of a complex matrix.

33. 9-th Conference of the International Linear Algebra Society.
     Technion-Israel Institute of Technology, Haifa, Israel (6/2001).
     Title: Numerical range of linear pencils.

34. Special session in ``Matrix Functions'',
     9-th Conference of the International Linear Algebra Society.
     Technion-Israel Institute of Technology, Haifa, Israel (6/2001).
     Title: On numerical range of matrix polynomials.

35. International Conference in Mathematical Analysis and its Applications.
     National Technical University of Athens, Greece (8/2000).
     Title: Numerical range of selfadjoint quadratic matrix polynomials.

36. 5-th Workshop on Numerical Ranges and Numerical Radii.
     Nafplio, Greece (6/2000).
     Title: Numerical range of matrix polynomials and joint numerical range.

37. 5-th Western Canada Linear Algebra Meeting.
     University of Winnipeg, Canada (5/2000).
     Title: Seminormal eigenvalues of matrix functions and numerical range.

38. International Workshop on Analysis of Vibrating Systems.
     Canmore, Canada (9/1999).
     Title: Boundary of the numerical range of selfadjoint quadratic matrix polynomials.

39. 8-th Conference of the International Linear Algebra Society (photo).
     Escola T`ecn. Superior d'Eng. Industrials, Barcelona, Spain (7/1999).
     Title: On factorization of matrix polynomials.

40. 4-th Western Canada Linear Algebra Meeting.
     University of Victoria, Canada (7/1998).
     Title: The boundary of numerical range of matrix polynomials.

41. 2-nd Panhellenic Conference in Algebra and Number Theory.
     University of Thessaloniki, Greece (6/1998).
     Title: On the connected components of numerical range of matrix polynomials.

42. 1-st Panhellenic Conference in Algebra.
     University of Athens, Greece (9/1996).
     Title: On the geometry of numerical range of matrix polynomials.

 OTHER ACTIVITIES

Member of the Scientific Organizing Committee,
18-th Conference of the International Linear Algebra Society.
University of Rhode Island, Providence, U.S.A. (6/2013).

Co-organizer of the special session in ``Matrix Polynomials and Related Problems'',
19-th International Workshop on Operator Theory and its Applications.
College of William and Mary, Williamsburg, Virginia, U.S.A. (7/2008).

Co-organizer of the 8-th Panhellenic Conference in Algebra and Number Theory.
National Technical University of Athens, Greece (5/2008).

Co-organizer of the special session in ``Matrix Functions'',
9-th Conference of the International Linear Algebra Society.
Technion-Israel Institute of Technology, Haifa, Israel (6/2001).

Co-organizer of the 5-th Workshop on Numerical Ranges and Numerical Radii.
Nafplio, Greece (06/2000).


Co-organizer of the 1-st Panhellenic Conference in Algebra.
University of Athens, Greece (9/1996).

 MATLAB FILES        

The file envelope.m estimates the spectrum envelope of a matrix.


The file nr.m estimates the boundary of the numerical range and the
eigenvalues of a matrix.


The file invnrp.m solves an inverse numerical range problem of a matrix.


The file polrange.m estimates the boundary of the numerical range and
the eigenvalues of a monic matrix polynomial.


The file pseinout.m estimates the boundary of the epsilon-pseudospectrum
and the eigenvalues of a matrix polynomial with nonsingular leading coefficient
(using exclusion discs centered at exterior and interior points).


The file pseout.m estimates the boundary of the epsilon-pseudospectrum
and the eigenvalues of a matrix polynomial with nonsingular leading coefficient
(using exclusion discs centered only at exterior points).


The file sqprange.m estimates the boundary of the numerical range and
the eigenvalues of a selfadjoint quadratic matrix polynomial with positive
definite leading coefficient.