Abstract
We consider the Hill operator
subject to periodic or antiperiodic boundary conditions, with potentials v which are trigonometric polynomials with nonzero coefficients, of the form
-
(i)
ae −2ix + be 2ix;
-
(ii)
ae −2ix + Be 4ix;
-
(iii)
ae −2ix + Ae −4ix + be 2ix + Be 4ix.
Then the system of eigenfunctions and (at most finitely many) associated functions is complete but it is not a basis in \({L^2 ([0,\pi], \mathbb{C})}\) if |a| ≠ |b| in the case (i), if |A| ≠ |B| and neither −b 2/4B nor −a 2/4A is an integer square in the case (iii), and it is never a basis in the case (ii) subject to periodic boundary conditions.
Similar content being viewed by others
References
Cameron, P.J.: Combinatorics: Topics, Techniques, Algorithms. Cambridge University Press (1994)
Dernek N., Veliev O.A.: On the Riesz basisness of the root functions of the nonself-adjoint Sturm-Liouville operator. Isr. J. Math. 145, 113–123 (2005)
Djakov, P., Mityagin, B.: Instability zones of periodic 1D Schrödinger and Dirac operators (Russian), Uspehi Mat. Nauk 61(4), 77–182 (2006) (English: Russian Math. Surveys 61(4), 663–766 (2006))
Djakov P., Mityagin B.: Asymptotics of instability zones of the Hill operator with a two term potential. J. Funct. Anal. 242(1), 157–194 (2007)
Djakov, P., Mityagin, B.: Bari–Markus property for Riesz projections of Hill operators with singular potentials. In: Aytuna, A., Meize, R., Terzioglu, T., Vogt, D. (eds.) Contemporary Mathematics, vol. 481, pp. 59–80. AMS, Functional Analysis and Complex Analysis (2009)
Dunford N.: A survey of the theory of spectral operators. Bull. Am. Math. Soc. 64, 217–274 (1958)
Dunford N., Schwartz J.: Linear Operators, Part III, Spectral Operators. Wiley, New York (1971)
Gesztesy F., Tkachenko V.: A criterion for Hill operators to be spectral operators of scalar type. J. d’Analyse Math. 107, 287–353 (2009)
Keselman G.M.: On the unconditional convergence of eigenfunction expansions of certain differential operators. Izv. Vyssh. Uchebn. Zaved. Mat. 39(2), 82–93 (1964) (Russian)
Levitan, B.M., Sargsjan, I.S.: Sturm-Liouville and Dirac operators. Translated from the Russian Mathematics and its Applications (Soviet Series), vol. 59. Kluwer Academic Publishers Group, Dordrecht (1991)
Magnus W., Winkler S.: Hill Equation. Interscience Publishers, John Wiley (1969)
Makin A.S.: On the convergence of expansions in root functions of a periodic boundary value problem. Dokl. Akad. Nauk 406(4), 452–457 (2006)
Makin, A.S.: On the basis property of system of root functions of regular boundary value problems for the Sturm—Liouville operator. Differ. Uravn. 42(12), 1646–1656, 1727 (2006) (Russian); English transl.: Differ. Equ. 42(12), 1717–1728 (2006)
Mamedov X.R., Kerimov N.B.: On Riesz basisness of root functions of regular boundary problems. Matem. Zamet. 64, 558–563 (1998)
Marchenko, V. A.: Sturm–Liouville Operators and their Applications, Kyiv, Naukowa Dumka (1977) (Russian); English transl.: in Operator Theory: Advances and Applications, vol. 22. Birkhaeuser, Boston (1986)
Mikhailov V.P.: On Riesz bases in L 2(0, 1). Dokl. Akad. Nauk SSSR 144, 981–984 (1962) (Russian)
Minkin A.: Equiconvergence theorems for differential operators. Functional Analysis, 4. J. Math. Sci. (NY) 96(6), 3631–3715 (1999)
Minkin A.: Resolvent growth and Birkhoff-regularity. J. Math. Anal. Appl. 323(1), 387–402 (2006)
Naimark, M.A.: Linear Differential Operators, Moscow, Nauka (1969) (Russian); (English transl.: Part 1, Elementary Theory of Linear Differential Operators, Ungar, New York (1967); Part 2: Linear Differential Operators in Hilbert Space, Ungar, New York (1968))
Savchuk A.M., Shkalikov, A.A.: Sturm—Liouville operators with distribution potentials (Russian) Trudy Mosk. Mat. Obs. 64, 159–212 (2003); English transl. in Trans. Moscow Math. Soc. 64, 143–192 (2003)
Shkalikov A.A.: The basis property of eigenfunctions of an ordinary differential operator. Uspekhi Mat. Nauk. 34, 235–236 (1979) (Russian)
Shkalikov A.A.: On the basisness property of eigenfunctions of ordinary differential operators with integral boundary conditions. Vestnik Mosk. Univ. Ser. 1. Math. Mech. 6, 12–21 (1982)
Shkalikov, A.A.: Boundary value problems for ordinary differential equations with a parameter in the boundary conditions, Trudy Sem. I. G. Petrovskogo 9, 190–229 (1983), (Russian); English transl.: J. Sov. Math. 33(6), 1311–1342 (1986)
Titchmarsh E.C.: Eigenfunction Expansions associated with Second-Order Differential Equations, Part II. Oxford University Press, Oxford (1958)
Van Lint, J.H., Wilson, R.M.: A Course in Combinatorics Cambridge University Press (1992)
Veliev O.A., Shkalikov A.A.: On Riesz basisness of eigenfunctions and associated functions of periodic and anti-periodic Sturm—Liouville problems. Matem. Zamet. 85, 671–686 (2009)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Djakov, P., Mityagin, B. Convergence of spectral decompositions of Hill operators with trigonometric polynomial potentials. Math. Ann. 351, 509–540 (2011). https://doi.org/10.1007/s00208-010-0612-5
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00208-010-0612-5