CURRENT POSITION / CONTACT INFO

Associate Professor
Department of Mathematics
National Technical University of Athens
Zografou Campus, 15780
Athens, GREECE
++ 210 772 1697
++ 210 772 1775 (FAX)
E-mail: ppsarr@math.ntua.gr

 PERSONAL

Born March 10, 1970 in Athens, Greece. Greek citizen.
Married to Sofia (Ntina) Vasileiadi.

 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 ranges, spectral analysis and canonical forms of
matrix polynomials (theory and numerics).
Linear dynamical systems, stability and pseudospectra.
Analysis of nonnegative matrices and Perron-Frobenius theory.
Hilbert spaces and indefinite inner product spaces.

 WORK EXPERIENCE

1/10 - present  Associate Professor, National Tech. University of Athens, Greece.
6/04 - 12/09    Assistant Professor, National Tech. University of Athens, Greece.
2/01 - 6/04      Visiting Lecturer, National Tech. University of Athens, Greece.
10/00 - 6/04    Visiting Lecturer, Tech. 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 Tech. University of Athens, Greece.
7/98 - 8/98      Research Visitor, University of Regina, Canada.
9/94 - 12/97    Teaching/Research Assistant, National Tech. Univ. of Athens, Greece.

 SUPERVISION

Michael Rokidis (current Ph.D. student, M.Sc. 2011).
Christos Chorianopoulos (Ph.D. 2011, M.Sc. 2007).
Nikolaos Papathanasiou (Ph.D. 2009, M.Sc. 2005).
Christina Michailidou (M.Sc. 2011).
Marianna Kouneli (M.Sc. 2010).
Stefanos Samaras (M.Sc. 2009).

 EDITORSHIP

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

 REFEREEING

Linear Algebra and its Applications.
Electronic Journal of Linear Algebra.
SIAM Journal on Matrix Analysis and Applications.
Linear and Multilinear Algebra.
Applied Mathematics Letters.
Integral Equations and Operator Theory.
Operator Theory: Advances and Applications.
Applied Mathematics and Computation.
Mathematical and Computer Modelling.

 PUBLICATIONS

 Refereed journal publications (published or accepted)

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


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

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


4. 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.

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


6. 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.


7. 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.


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

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


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


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

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

13. 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.

14. Gregory Kalogeropoulos and Panayiotis Psarrakos.
     The polar decomposition of block companion matrices.
     Computers Math. Appl., v. 50 (2005), pp. 529-537.

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

16. 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.

17. 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.

18. 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.

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

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

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

22. 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.

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

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

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

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

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

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

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

30. 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.

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

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

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

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

35. 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.

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

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

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

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

40. Panayiotis Psarrakos.
     Numerical range of linear pencils.
     Linear Algebra Appl., v. 317 (2000), pp. 127-142.

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

42. 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.

43. 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.

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

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

46. 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.

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


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


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


50. John Maroulas and Panayiotis Psarrakos.
     Geometrical properties of numerical range of matrix polynomials.
     Computers Math. Appl., v. 31 (1996), pp. 41-47.

 PhD Thesis

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

 Book

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

 Lecture Notes

Panayiotis Psarrakos.
Topics in Matrix Analysis (in Greek, 151+vi pages).
Publications of National Technical University of Athens, 2012.

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.

Contributing author, with E. Rappos, P. Vlamos, et al.
Partitions of integer numbers in international mathematical olympiads (in Greek).
Mathimatiki Epitheorisi of Greek Mathematical Society, v. 51 (1999), pp. 113-129.

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


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

 Contributed talks

1. Conference in Numerical Analysis (NumAn 2010), 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.

2. 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.

3. 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.

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

5. 19-th International Workshop on Operator Theory and its Applications.
    College of William and Mary, Williamsburg, U.S.A. (7/2008).
    Title: Normal matrix polynomials.

6. 9-th Workshop on Numerical Ranges and Numerical Radii (photo).
    College of William and Mary, Williamsburg, U.S.A. (7/2008).
    Title: A definition of numerical range based on the Birkhoff-James orthogonality.

7. 8-th Panhellenic Conference in Algebra and Number Theory.
    National Technical University of Athens, Greece (5/2008).
    Title: Normal matrix polynomials.

8. 12-th Panhellenic Conference in Mathematical Analysis.
    University of Athens, Greece (5/2008).
    Title: Pseudospectra of matrix polynomials and their boundaries.

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

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

11. 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.

12. 10-th Panhellenic Conference in Mathematical Analysis.
     National Technical University of Athens, Greece (10/2004).
     Title: Pseudospectra of polynomial eigenvalue problems.

13. 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.

14. 11-th Conference of the International Linear Algebra Society (photo).
     University of Coimbra, Portugal (7/2004).
     Title: On the pseudospectra of matrix polynomials.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 9-th Conference of the International Linear Algebra Society.
     Technion-Israel Institute of Technology, Haifa, Israel (6/2001).
     Title: Numerical range of linear pencils.

21. 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.

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

23. 5-th Workshop on Numerical Ranges and Numerical Radii.
     Nafplio, Greece (6/2000).
     Title: Numerical range of matrix polynomials and joint numerical range.

24. 5-th Western Canada Linear Algebra Meeting.
     University of Winnipeg, Canada (5/2000).
     Title: Seminormal eigenvalues of matrix functions and numerical range.

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

26. 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.

27. 4-th Western Canada Linear Algebra Meeting.
     University of Victoria, Canada (7/1998).
     Title: The boundary of numerical range of matrix polynomials.

28. 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.

29. 1-st Panhellenic Conference in Algebra.
     University of Athens, Greece (9/1996).
     Title: On the geometry of numerical range of matrix polynomials.

 OTHER ACTIVITIES

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, 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 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.