Abstract
The existence or non-existence of positive orthogonal functions for subspaces of almost periodic functions has important applications in studying the oscillatory behavior of vibrations. Haraux and Komornik have obtained a number of theorems of this type. The purpose of this paper is to answer an open question formulated in the 1980s, and to completely clarify the situation for subspaces defined by three periods.
Similar content being viewed by others
Notes
The value \(\ell =-1\) is not used here but we will need it later.
References
Haraux, A., Komornik, V.: Oscillations of anharmonic Fourier series and the wave equation. Rev. Mat. Iberoamericana 1(4), 57–77 (1985)
Haraux, A., Komornik, V.: Oscillations in the wave equation, Nonlinear partial differential equations and their applications. Collége de France seminar, vol. VIII (Paris, 1984–1985). Pitman Res. Notes Math. Ser. 166, 110–119 (1988)
Haraux, A., Komornik, V.: On the vibrations of rectangular plates. Proc. Roy. Soc. Edinburgh Sect. A 119A, 47–62 (1991)
Kahane, J.P.: Lectures on Mean Periodic Functions, Tata Institute of Fundamental Research Lectures on Mathematics and Physics, No. 15, Bombay (1959)
Komornik, V.: Density theorems for almost periodic functions. A Hilbert space approach. J. Math. Anal. Appl. 122, 538–554 (1987)
Komornik, V.: On the vibrations of a square membrane. Proc. Roy. Soc. Edinburgh Sect. A 111A, 13–20 (1989)
Komornik, V.: On the vibrations of solid balls. Acta Math. Hungar. 54, 309–317 (1989)
Komornik, V.: On the vibrations of a spherical membrane. Houston J. Math. 16, 187–193 (1990)
Komornik, V.: On the vibrations of rectangular membranes. Differ. Integral Equ. 6, 319–327 (1993)
Acknowledgements
The author wants to express his gratitude to Vilmos Komornik for his useful comments and suggestions and Peter Mueller for his help in the proof of Proposition (7.2). He also thanks Mohamad Maassarani for fruitful discussions.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Hans G. Feichtinger.
Rights and permissions
About this article
Cite this article
Delage, F. On the Orthogonal of a Sum of Periodic Function Spaces. J Fourier Anal Appl 24, 1204–1224 (2018). https://doi.org/10.1007/s00041-017-9580-4
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00041-017-9580-4