The Density Theorem and the Homogeneous Approximation Property for Gabor Frames

  • Christopher Heil
Part of the Applied and Numerical Harmonic Analysis book series (ANHA)


The Density Theorem for Gabor frames is a fundamental result in time-frequency analysis. Beginning with Baggett’s proof that a rectangular lattice Gabor system {e2πiβntg(t − αk)}n,kZ must be incomplete in L2(R) whenever αβ > 1, the necessary conditions for a Gabor system to be complete, a frame, a Riesz basis, or a Riesz sequence have been extended to arbitrary lattices and beyond. The first partial proofs of the Density Theorem for irregular Gabor frames were given by Landau in 1993 and by Ramanathan and Steger in 1995. A key fact proved by Ramanathan and Steger is that irregular Gabor frames possess a certain Homogeneous Approximation Property (HAP), and that the Density Theorem is a consequence of this HAP. This chapter provides a brief history of the Density Theorem and a detailed account of the proofs of Ramanathan and Steger. Furthermore, we show that the techniques of Ramanathan and Steger can be used to give a full proof of a general version of Density Theorem for irregular Gabor frames in higher dimensions and with finitely many generators.


Density Theorem Dual Frame Gabor Frame Gabor System Rectangular Lattice 
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Copyright information

© Birkhäuser Boston 2008

Authors and Affiliations

  • Christopher Heil
    • 1
  1. 1.School of MathematicsGeorgia Institute of TechnologyAtlanta

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