Abstract
The Fourier transform is typically seen as closely related to the additive group of real numbers, its characters and its Haar measure. In this paper, we propose an alternative viewpoint; the Fourier transform can be uniquely characterized by an intertwining relation with dilations and by having a Gaussian as an eigenfunction. This broadens the perspective to an entire family of Fourier-like transforms that are uniquely identified by the same dilation-related property and by having Gaussian-like functions as eigenfunctions. We show that these transforms share many properties with the Fourier transform, particularly unitarity, periodicity and eigenvalues. We also establish short-time analogues of these transforms and show a reconstruction property and an orthogonality relation for the short-time transforms.

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References
Abramowitz, M., Stegun, I.A.: Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables. Dover, New York (1972)
Akhiezer, N.I.: Lectures on Integral Transforms. American Mathematical Society, Providence (1988)
Boche, H.: Eine axiomatische Charakterisierung der Hilbert-transformation. Acta Mathematica et Informatica Universitatis Ostraviensis 8, 11–23 (2000)
Bodmann, B.G., Papadakis, M., Sun, Q.: An inhomogeneous uncertainty principle for digital low-pass filters. J. Fourier Anal. Appl. 12(2), 181–211 (2006)
Daubechies, I.: Ten Lectures on Wavelets, vol. 61 of CBMS-NSF Regional Conference Series in Applied Mathematics. Society for Industrial and Applied Mathematics (SIAM), Philadelphia, PA, (1992)
de Gosson, M.A.: Symplectic Methods in Harmonic Analysis and in Mathematical Physics. Pseudo-Differential Operators, vol. 7. Theory and Applications. Birkhäuser/Springer Basel AG, Basel (2011)
Folland, G.B.: Harmonic analysis in phase space. Annals of Mathematics Studies, vol. 122. Princeton University Press, Princeton (1989)
Ghobber, S., Jaming, P.: The Logvinenko–Sereda theorem for the Fourier–Bessel transform. Integral Trans. Spec. Funct. 24(6), 470–484 (2013)
Grafakos, L.: Classical Fourier Analysis: Graduate Texts in Mathematics, 3rd edn. Springer, New York (2014)
Grafakos, L., Teschl, G.: On Fourier transforms of radial functions and distributions. J. Fourier Anal. Appl. 19(1), 167–179 (2013)
Gröchenig, K.: Foundations of Time-Frequency Analysis. Birkhäuser, Boston (2001)
Rösler, M., Voit, M.: An uncertainty principle for Hankel transforms. Proc. Am. Math. Soc. 127, 183–194 (1999)
Rudin, W.: Functional Analysis. McGraw-Hill, New York (1991)
Stein, E., Weiss, G.: Introduction to Fourier Analysis on Euclidean Spaces. Princeton University Press, Princeton (1971)
Watson, G.N.: A Treatise on the Theory of Bessel Functions. Cambridge University Press, Cambridge, U.K. (1944)
Acknowledgments
The authors would like to thank the referees for insightful comments that helped improve this paper. All authors gratefully acknowledge partial support of this research by grants from Total E&P USA and Petroleum Geo-Services. B.G.B. was supported in part by NSF Grant DMS-1412524. C.L.W. and D.J.K. acknowledge partial support of this research under Grant E-0608 from the Robert A. Welch Foundation.
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Communicated by Hans G. Feichtinger.
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Williams, C.L., Bodmann, B.G. & Kouri, D.J. Fourier and Beyond: Invariance Properties of a Family of Integral Transforms. J Fourier Anal Appl 23, 660–678 (2017). https://doi.org/10.1007/s00041-016-9482-x
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DOI: https://doi.org/10.1007/s00041-016-9482-x