RESEARCH PUBLICATIONS

1.      K. Ifantis, Uber das Eigenwertproblem der Funktional Gleichung f(x+a)+f(x-a)=2(E-b\x)f(x), Zeits. Angew. Math. Mech. 48, (1968),66-68 (German)

  1. E. K. Ifantis and P. C. Deliyiannis, Spectral Theory of the Difference Equation f(n+1)+f(n-1)=(E-ö(n))f(n), J. Math. Phys. 10, (1969), 421-425
  2. E. K. Ifantis, Spectral Theory of Tridiagonal operators, Bull. Greek Math. Soc. 10, (1969),89-125. (In Greeks)
  3. E. K. Ifantis, Structure of the Point spectrum of Schrodinger- Type Tridiagonal Operators, J. Math. Phys. 11, (1970), 3138-3144
  4. E. K. Ifantis, Abstract Formulation of the Quantum Mechanical oscillator Phase Problem. J. Math. Phys. 12, (1971), 1021-1026
  5. E. K. Ifantis, Solution of the Schrodinger Equation in the Hardy-Lebesgue Space, J. Math. Phys. 12, (1971), 1961-1965
  6. E. K. Ifantis, Minimal Uncertainty States for bounded Observables, J. Math. Phys. 12, (1971), 2512-2516
  7. E. K. Ifantis, On the Nature of the Spectrum of generalized oscillator Phase Operators, Letters all Nouvo Cimento, 2, (1971), 1096-1100
  8. E. K. Ifantis, States, minimizing the Uncertainty Product of the oscillator Phase Operators, J. Math. Phys. 13, (1972), 568-575
  9. E. K. Ifantis and C. B. Kouris, Study of Differential Equations of Mathematical Physics in the Hardy-Lebesgue Space, J. Math. Phys. 13, (1972), 1193-1195.
  10. E. K. Ifantis, Perturbation of Isometries, Duke Mathematical Journal, 39, (1972), 735-736.
  11. E. K. Ifantis and C. B. Kouris, A Hilbert Space approach to the Localization problem of the roots of Analytic Functions, Indiana University Mathematics Journal, 23, (1973), 11-22.
  12. E. K. Ifantis and C. B. Kouris, Lower Bounds for the Zeros of Analytic Functions, Numer. Math. 27, (1976), 239-247.
  13. E. K. Ifantis, An Existence Theory for Functional-Differential Equations and Functional-Differential Systems, Jour. Diff. Equations, 29, (1978), 86-104.
  14. E. K. Ifantis, and P. D. Siafarikas, and C. B. Kouris, Conditions for Solutions of a linear First-Order Differential Equation in the Hardy- Lebesgue Space and Applications, Jour. Math. Anal. Appl. 104 (1984), 454-466.
  15. E. K. Ifantis and P. D. Siafarikas, An Inequality relating the zeros of two Ordinary Bessel Functions, Applicable Analysis, 19, (1985), 251-263.
  16. E. K. Ifantis and P. D. Siafarikas, A Differential Equation for the Zeros of Bessel Functions, Applicable Analysis, 20, (1985), 269-281.
  17. E. K. Ifantis and P. D. Siafarikas, Ordering Relations Between the Zeros of Miscellaneous Bessel Functions, Applicable Analysis, 23, (1986), 85-110.
  18. E. K. Ifantis and P. D. Siafarikas, A Functional Analytic Approach for the study of the zeros of Bessel Functions, Linear Algebra Appl. 84, (1986),391-397.
  19. E. K. Ifantis and P. D. Siafarikas, Upper Bounds for the Zeros of Bessel Functions, Journal of Computational and Applied Mathematics, 17, (1987), 355-358.
  20. E. K. Ifantis, Analytic Solutions for Nonlinear Differential Equations, Journal of Mathematical Analysis and Applications, 124 (2), (1987), 339-380.
  21. E. K. Ifantis, Global Analytic Solutions of the Radial Nonlinear Wave Equation, Journal of Mathematical Analysis and Applications, 124 (2), (1987), 381-3-410.
  22. E. K. Ifantis, On the Convergence of Power series Whose Coefficients Satisfy a Poincare-type linear and non linear Difference Equation, Complex Variables, 9, (1987), 63-80.
  23. E. K. Ifantis and P. D. Siafarikas, A Differential Equation for the Positive Zeros of the Function $\alpha J\sb v(z)+\gamma zJ'\sb v(z)$, Zeitschrist fur Analysis and Ihre Anwendungen, 7 (2), (1988), 185-192.
  24. E. K. Ifantis, P. D. Siafarikas and C. B. Kouris, The Imaginary zeros of a mixed Bessel Function, Journal of Applied Mathematics and Physics, 39, (1988), 157-165.

26.  E. K. Ifantis, A Theorem Concerning Differentiability of Eigenvectors and Eigenvalues with some Applications, Applicable Analysis, 28 (1988), 257-283.

  1. E. K. Ifantis and P. D. Siafarikas, Bounds for the first positive Zero of a mixed Bessel Function, Journal of Computational and Applied Mathematics, 21, (1988), 245-249.
  2. E. K. Ifantis and P. D. Siafarikas, Differential Inequalities on the greatest Zeros of Laguerre and Ultraspherical Polynomials, Actas del VI Simposium on Polinomios Orthogonales Y aplicationes, Gilon, Spain, (1989), 187-197.
  3. E. K. Ifantis and P. D. Siafarikas, A result on the Imaginary Zeros of $J"\sb \nu(z)$, Journal of Approximation Theory, 62 (2), (1990), 192-196.
  4. E. K. Ifantis and P. D. Siafarikas, Inequalities involving Bessel and Modified Bessel Functions, Journal Math. Anal. Appl. 147, (1990), 214-227.
  5. E. K. Ifantis and P. D. Siafarikas, Differential Inequalities for the positive zeros of Bessel Functions, Journal of Computational and Applied Mathematics, 30, (1990),139-143.
  6. E. K. Ifantis and P. N. Panagopoulos, Applications of the differentiability of eigenvectors and eigenvalues to a perturbed harmonic oscillator, Jour. Math. Physics, 31, (1990), 2410-2413.
  7. E. K. Ifantis and P. D. Siafarikas, Bounds of Modified Bessel Functions, Rendiconti del Circolo Matematico Di Palermo, Serie II, Tomo XL, (1991), 347-356.
  8. E. K. Ifantis, Concavity and Convexity of Eigenvalues, Applicable Analysis, 41, (1991), 209-220.
  9. E. K. Ifantis and C. G. Kokologiannaki and C. B. Kouris, On the Positive zeros of the second derivative of Bessel functions, Journal of Computational and Applied Math. 34, (1991), 21-31.
  10. E. K. Ifantis, Perron-Frobenious-Type Theorems for Tridiagonal Operators, Applicable Analysis, 44, (1992), 159-169.
  11. E. K. Ifantis and P. D. Siafarikas, A Differential Inequality for the positive zeros of Bessel Functions, Journal of Computational and Applied Math., 44, (1992), 115-120.
  12. E. K. Ifantis and P. D. Siafarikas, and A. P. Jannusis, Entire Solution of a Second Order Linear Differential Equation, Complex Variables, 22, (1993), 23-26,.
  13. E. K. Ifantis and P. D. Siafarikas, On the Zeros of a Class of Polynomials including the generalized Bessel Polynomials, Proceedings of the Seventh Spanish Symposium on Orthogonal Polynomials and Applications (VII SPOA) (Granada, 1991), Jour. Comp. Appl. Math. 49. (1993), 103-109.
  14. E. K. Ifantis and C. G. Kokologiannaki, Location of the complex zeros of Bessel functions, Zeits. fur Analysis und Ihre Andwendungen, 12 (4), (1993), 605-612.
  15. E. K. Ifantis and P. N. Panagopoulos, On the Zeros of a Class of Polynomials, J. Math. Anal. Appl. 182 (2), (1994), 361-370.
  16. E. K. Ifantis and P. D. Siafarikas, Perturbation of the Coefficients in the recurrence relation of a Class of Polynomials, J. Comp. Appl. Math. 57, (1995), 163-170.
  17. E. K. Ifantis and P. D. Siafarikas, Differential Inequalities and Monotonicity Properties of the Zeros of Associated Laquerre and Hermite Polynomials, Annals Numer. Math. 2, (1995), 79-91.
  18. E. K. Ifantis and P. D. Siafarikas, An Alternative proof of a theorem of Stieltjes and related results, J. Comp. Appl. Math. 65, (1995), 165-172.
  19. E. K. Ifantis and P. D. Siafarikas and C. G. Kokologiannaki, Newton sum rules and monotonicity properties of zeros of scaled co-recursive associated polynomials, Methods and Applications of Analysis, 3 (4), (1996), 486-497.
  20. E. K. Ifantis, A criterion for the non-uniqueness of the measure of orthogonality, Jour. Appr. Theory, 89, (1997), 207-218.
  21. E. K Ifantis and K. N. Vlachou, Some results, concerning the variation of eigenvalues, when these depend on a real parameter. Appl. Anal. 74 (2000), no. 1-2, 113-125.
  22. E. K. Ifantis and P. N. Panagopoulos, Convergence of associated continued fractions revised. Acta Appl. Math. 66 (2001), no. 1, 1-24.
  23. E. K. Ifantis and P. N. Panagopoulos, Limit points of eigenvalues of truncated tridiagonal operators, J. Comp. Appl. Math. 133 (1-2) (2001), 413-422 (Special Issue: Orthogonal Polynomials, Special Functions and their Applications)
  24. E. K. Ifantis, On the spectral measure of a class of orthogonal polynomials, Open Problem, J. Comp. Appl. Math. 133 (1-2) (2001), 688-689 (Special Issue: Orthogonal Polynomials, Special Functions and their Applications)
  25. E. K. Ifantis, P. D. Siafarikas, A counterexample to an assertion due to Blumenthal. Univ. Iagel. Acta Math. Vol.. 39 (2001), 249-254.
  26. E. K. Ifantis, C. G. Kokologiannaki and P. D. Siafarikas, On the support of the measure of orthogonality of a class of orthogonal polynomials, Applied Mathematics and Computation Vol. 128 (2-3) (2002), 275-288.
  27. E. K. Ifantis and K. N. Vlachou, Solution of the semi-infinite Toda lattice for unbounded sequences, Lett. Math. Phys. Vol. 59 (2002), 1-17
  28. E. K. Ifantis and C. G. Kokologiannaki, Stieltjes transforms of a class of probability measure, J. Comput. Appl. Math. Vol.153 (2003), no. 1-2, 249–258
  29. E. K. Ifantis and K. N. Vlachou, Exact solutions of the semi-infinite Toda lattice with applications to the inverse spectral problem, Absr. Appl. Anal. 2004, no. 5, 435-451.
  30. E. K. Ifantis, C. G. Kokologiannaki and E. Petropoulou, Limit points of eigenvalues of truncated unbounded tridiagonal operators, Cent. Eur. J. Math. Vol. 5 (2007), no. 2, 335–344.