Toeplitz Operators with Frequency Modulated Semi-Almost Periodic Symbols

A. Böttcher, S. Grudsky, I. Spitkovsky

Research output: Contribution to journalArticlepeer-review


It is well known that amplitude modulation does not affect Fredholmness of Toeplitz operators. The same is true for frequency modulation provided the symbol of the operator is piecewise continuous. In this article, it is shown that frequency modulation can destroy Fredholmness for Toeplitz operators with almost periodic symbols; the corresponding example is based on the observation that certain almost periodic functions become semi-almost periodic functions after appropriate frequency modulation. Moreover, this article contains several results that can be employed in order to decide whether a Toeplitz operator with a frequency modulated semi-almost periodic symbol is Fredholm.

Original languageEnglish (US)
Pages (from-to)523-535
Number of pages13
JournalJournal of Fourier Analysis and Applications
Issue number5
StatePublished - 2001


  • Almostperiodic function
  • Fredholm operator
  • Frequency modulation
  • Semi-almost periodic function
  • Toeplitz operator

ASJC Scopus subject areas

  • Analysis
  • General Mathematics
  • Applied Mathematics


Dive into the research topics of 'Toeplitz Operators with Frequency Modulated Semi-Almost Periodic Symbols'. Together they form a unique fingerprint.

Cite this