List of Publications

  1. A. Gheondea: On meromorphic functional calculus [Romanian], Studii si Cercetari Matematice, 33(1981), 171-191.
  2. T. Constantinescu and A. Gheondea: Algebraic aspects of the functional calculus for meromorphic functions, Revue Roumaine de Mathematiques Pures et Appliquees, 27(1982), 949-956.
  3. Gr. Arsene and A. Gheondea: Completing matrix contractions, Journal of Operator Theory, 7(1982), 179-189.
  4. A. Gheondea: Pseudo-regular spectral functions, Journal of Operator Theory, 12(1984), 349-358.
  5. A. Gheondea: On the geometry of pseudo-regular subspaces of a Krein space, in Operator Theory: Advances and Applications, Vol. 14, Birkhauser Verlag, Basel 1984, pp. 141-156.
  6. A. Gheondea and P. Jonas: A characterization of spectral functions of definitizable operators, Journal of Operator Theory, 17(1987), 99-110.
  7. T. Constantinescu and A. Gheondea: On unitary dilation and characteristic functions in indefinite inner product spaces, in Operator Theory: Advances and Applications, Vol. 24, Birkhauser Verlag, Basel 1987, pp. 87-102.
  8. Gr. Arsene, T. Constantinescu and A. Gheondea: Lifting of operators and prescribed negative squares, Michigan Mathematical Journal, 34(1987), 201-216.
  9. A. Gheondea: Canonical forms of unbounded unitary operators in Krein spaces, Publications of the Research Institute of Mathematical Sciences, Kyoto University, 24(1988), 205-224.
  10. A. Gheondea: On invariant maximal non-negative subspaces of certain operators acting in Krein space, Integral Equations and Operator Theory, 12(1989), 129-195.
  11. A. Gheondea: A geometric question concerning strong duality of neutral subspaces, Mathematica Balkanica, 3(1989), 183-195.
  12. T. Constantinescu and A. Gheondea: Minimal signature in lifting of operators. I, Journal of Operator Theory, 22(1989), 345-367.
  13. A. Gheondea: On the structure of linear contractions with respect to fundamental decompositions, in Operator Theory: Advances and Applications Vol. 48, Birkhauser Verlag, Basel 1990, pp. 275-295.
  14. T. Constantinescu and A. Gheondea: Minimal signature in lifting of operators. II, Journal of Functional Analysis, 103(1992), 317-351.
  15. A. Gheondea: One-step completions of Hermitian partial matrices with minimal negative signature, Linear Algebra and its Applications, 173(1992), 99-114.
  16. T. Constantinescu and A. Gheondea: Extending factorizations and minimal negative signatures, Journal of Operator Theory, 28(1992), 371-402.
  17. T. Constantinescu and A. Gheondea: The negative signature of some Hermitian matrices, Linera Algebra and its Applications, 178(1993), 178-42.
  18. A. Gheondea: Quasi-contractions in Krein spaces, in Operator Theory: Advances and Applications, Vol. 61, Birkhauser Verlag, Basel 1993, pp. 123-148.
  19. A. Gheondea: The spectral theory of selfadjoint operators in Krein spaces [Romanian], Studii si Cercetari Matematice, 45(1993), 177-265.
  20. A. Gheondea: Techniques of geometry of Krein spaces in generalized interpolation theory, in Challanges of a Generalized System Theory, North-Holland, Amsterdam 1993, pp.195-208.
  21. T. Constantinescu and A. Gheondea: Elementary rotations of linear operators in Krein spaces, Journal of Operator Theory, 29(1993), 167-203.
  22. T. Constantinescu and A. Gheondea: Extending chains of factorizations and minimal negative signatures, Zeitschrift fur Analysis und ihre Anwendungen, 13(1994), 137-153.
  23. T. Constantinescu and A. Gheondea: On the indefinite trigonometric problem of I. S. Iokhvidov and M. G. Krein, Mathematische Nachrichten, 171(1995), 79-94.
  24. A. Dijksma and A. Gheondea: On the signatures of selfadjoint pencils, in Operator Theory: Advances and Applications, Vol. 80, Birkhauser Verlag, Basel 1995.
  25. A. Dijksma and A. Gheondea: Index formula for subspaces of Krein spaces, Integral Equations and Operator Theory, 25(1996), 58-72.
  26. A. Gheondea: Contractive intertwining dilations of quasi-contractions, Zeitschrift fur Analysis und ihre Anwendungen, 15(1996), 31-44.
  27. T. Constantinescu, A. Gheondea: Hermitian kernels with bounded structure, Integral Equations and Operator Theory, 27(1997), 141-164.
  28. A. Gheondea, R.J. Ober: Spectral Minimality of J-Positive Linear Systems of Finite Order, in Operators, Linear Systems, and Linear Algebra, B.G. Teubner Stuttgart 1997, pp. 70--80.
  29. T. Constantinescu, A. Gheondea: Representation of Hermitian kernels by means of Krein spaces, Publ. RIMS Kyoto University, 33(1997), 917--951.
  30. A. Gheondea: On Generalized Interpolation and Shift Invariant Maximal Semidefinite Subspaces, in Operator Theory: Advances and Applications, Vol. 103, Birkhauser Verlag, Basel-Boston-Berlin 1998.
  31. T. Constantinescu, A. Gheondea: On a Nehari type problem on spaces with indefinite inner product, Revue Roumaine Math. Pures Appl., 43(1998), 323--354..
  32. T. Constantinescu, A. Gheondea: On the Caratheodory type problem of M.G. Krein and H. Langer, C. R. Acad. Sci. Paris I, 327(1998), 243--247.
  33. A. Gheondea, R.J. Ober: Completely J-positive linear systems of finite order, Mathematische Nachrichten, 203(1999), 75-101.
  34. A. Gheondea, R.J. Ober: A trace formula for Hankel operators, Proceedings of the American Mathematical Society, 127(1999), 2007-2012.
  35. T. Constantinescu, A. Gheondea: Kolmogorov decompositions and the realization of time dependent systems, in Operator Theory: Advances and Applications, Vol. 115, pp. 123-144; Birkhauser Verlag, Basel-Boston, 2000.
  36. A. Gheondea, R.J. Ober: A note on the existence, uniqueness and symmetry of parbalanced realizations, Integral Equations and Operator Theory, 37(2000), 423-436.
  37. B. Curgus, A. Gheondea, H. Langer: On singular critical points of definitizable operators, Proceedings of the American Mathematical Society , 128(2000), 2621-2626.
  38. T. Constantinescu, A. Gheondea: On the Schur algorithm and coefficient characterizations for generalized Schur functions, Proceedings of the American Mathematical Society , 128(2000), 2705-2713.
  39. T. Constantinescu, A. Gheondea: Invariant Hermitian kernels and their Kolmogorov decompositions, Comptes Rendus de l'Academie des Sciences, serie I-Mathematiques, 331(2000), no. 10, 797--802.
  40. T. Constantinescu, A. Gheondea: Representations of Hermitian kernels by means of Krein spaces II. Invariant kernels, Communications in Mathematical Physics, 216(2001), no. 2, 409--430.
  41. A. Arias, A. Gheondea, and S. Gudder: Fixed points of quantum operations, J. Mathematical Physics, 43(2002), no. 12, 5872--5881.
  42. A. Gheondea and G. Popescu: Bounded characteristic functions and models for noncontractive sequences of operators, Integral Equations and Operator Theory, 45(2003), 15--38.


    43. Accepted papers


  43. A. Gheondea and G. Popescu: Joint similarity and dilations for noncontractive sequences of operators, Journal of Functional Analysis, PS file, PDF file.
  44. A. Gheondea and S. Gudder: Sequential product of quantum effects, Proceedings of the American Mathematical Society,PS file, PDF file.
  45. A. Gheondea and R.N. Gologan: On a class of piecewise smooth functions Bulletin de Mathematique de la Societe des Sciences Mathematiques de Roumanie, PS file, PDF file.


    46. Preprints


  46. T. Constantinescu and A. Gheondea: L. Schwartz's boundedness condition, invariant kernels, and dilation theory, PS file, PDF file, (Posted also at http://arxiv.org/abs/math.FA/0212218).