Abstract
The characteristic functional is the infinite-dimensional generalization of the Fourier transform for measures on function spaces. It characterizes the statistical law of the associated stochastic process in the same way as a characteristic function specifies the probability distribution of its corresponding random variable. Our goal in this work is to lay the foundations of the innovation model, a (possibly) non-Gaussian probabilistic model for sparse signals. This is achieved by using the characteristic functional to specify sparse stochastic processes that are defined as linear transformations of general continuous-domain white Lévy noises (also called innovation processes). We prove the existence of a broad class of sparse processes by using the Minlos–Bochner theorem. This requires a careful study of the regularity properties, especially the \(L^p\)-boundedness, of the characteristic functional of the innovations. We are especially interested in the functionals that are only defined for \(p<1\) since they appear to be associated with the sparser kind of processes. Finally, we apply our main theorem of existence to two specific subclasses of processes with specific invariance properties.
Similar content being viewed by others
References
Alpay, D., Jorgensen, P.E.T.: Stochastic processes induced by singular operators. Numer. Funct. Anal. Optim. 33(7–9), 708–735 (2012)
Amini, A., Kamilov, U.S., Bostan, E., Unser, M.: Bayesian estimation for continuous-time sparse stochastic processes. IEEE Trans. Signal Process. 61(4), 907–920 (2013)
Anh, V.V., Ruiz-Medina, M.D., Angulo, J.M.: Covariance factorisation and abstract representation of generalised random fields. Bull. Aust. Math. Soc. 62(02), 319–334 (2000)
Amini, A., Unser, M., Marvasti, F.: Compressibility of deterministic and random infinite sequences. IEEE Trans. Signal Process. 59(11), 5193–5201 (November 2011)
Biermé, H., Estrade, A., Kaj, I.: Self-similar random fields and rescaled random balls models. J. Theor. Probab. 23(4), 1110–1141 (2010)
Bostan, E., Fageot, J., Kamilov, U.S., Unser., M.: Map estimators for self-similar sparse stochastic models. In: Proceedings of the Tenth International Workshop on Sampling Theory and Applications (SampTA’13), Bremen, Germany, (2013)
Bostan, E., Kamilov, U.S., Nilchian, M., Unser, M.: Sparse stochastic processes and discretization of linear inverse problems. IEEE Trans. Image Process. 22(7), 2699–2710 (2013)
Bostan, E., Kamilov, U.S., Unser, M.: Reconstruction of biomedical images and sparse stochastic modeling. In: Proceedings of the Ninth IEEE International Symposium on Biomedical Imaging: From Nano to Macro (ISBI’12), pp. 880–883, Barcelona, Spain, May 2–5,( 2012)
Bony, J.-M.: Cours d’analyse–Théorie des distributions et analyse de Fourier. Les éditions de l’Ecole Polytechnique (2001)
Bel, L., Oppenheim, G., Robbiano, L., Viano, M.C.: Linear distribution processes. Int. J. Stoch. Anal. 11(1), 43–58 (1998)
Candès, E.J., Romberg, J., Tao, T.: Robust uncertainty principles: exact signal reconstruction from highly incomplete frequency information. IEEE Trans. Inf. Theory 52(2), 489–509 (2006)
Donoho, D.L.: Compressed sensing. IEEE Trans. Inf. Theory 52(4), 1289–1306 (2006)
Gribonval, R., Cevher, V., Davies, M.E.: Compressible distributions for high-dimensional statistics. IEEE Trans. Inf. Theory 58(8), 5016–5034 (2012)
Gelfand, I.M.: Generalized random processes. Dokl. Akad. Nauk. SSSR 100, 853–856 (1955)
Grothendieck, A.: Produits tensoriels topologiques et espaces nucléaires. Number 16. American mathematical society (1955)
Gelfand, I.: Generalized Functions. Applications of Harmonic Analysis, vol. 4. Academic press, New York (1964)
Kamilov, U.S., Pad, P., Amini, A., Unser, M.: MMSE estimation of sparse Lévy processes. IEEE Trans. Signal Process. 61(1), 137–147 (2013)
Mallat, S.: A Wavelet Tour of Signal Processing. Academic Press, San Diego (1999)
Mumford, D., Gidas, B.: Stochastic models for generic images. Q. Appl. Math. 59(1), 85–112 (2001)
Mandelbrot, B.B., Van Ness, J.W.: Fractional Brownian motions, fractional noises and applications. SIAM Rev. 10(4), 422–437 (1968)
Pad, P., Unser, M.: On the optimality of operator-like wavelets for sparse ar(1) processes. In: Proceedings of the Thirty-Eight IEEE International Conference on Acoustics. Speech and Signal Processing (ICASSP’13) 59(8), 5063–5074 (2013)
Ruiz-Medina, M.D., Angulo, J.M., Anh, V.V.: Fractional generalized random fields on bounded domains. Stochastic Anal. Appl. 21(2), 465–492 (2003)
Rudin, W.: Functional Analysis. International Series in Pure and Applied Mathematics. McGraw-Hill Inc, New York (1991)
Sato, K.-I.: Lévy Processes and Infinitely Divisible Distributions. Chapman & Hall, New York (1994)
Schwartz, L.: Théorie Des Distributions. Hermann, Paris (1966)
Srivastava, A., Lee, A.B., Simoncelli, E.P., Zhu, S.C.: On advances in statistical modeling of natural images. J. Math. Imag. Vis. 18(1), 17–33 (2003)
Samorodnitsky, G., Taqqu, M.S.: Stable Non-Gaussian Processes: Stochastic Models with Infinite Variance. Chapman and Hall, New York (1994)
Sun, Q., Unser, M.: Left-inverses of fractional Laplacian and sparse stochastic processes. Adv. Comput. Math. 36(3), 399–441 (2012)
Treves, F.: Topological vector spaces, distributions and kernels. Academic Press, New York (1967)
Tafti, P.D., Van De Ville, D., Unser, M.: Invariances, Laplacian-like wavelet bases, and the whitening of fractal processes. IEEE Trans. Image Process. 18(4), 689–702 (2009)
Unser, M., Tafti, P.D.: Stochastic models for sparse and piecewise-smooth signals. IEEE Trans. Signal Process. 59(3), 989–1006 (2011)
Unser, M., Tafti, P.D., Amini, A., Kirshner, H.: A unified formulation of gaussian versus sparse stochastic processes—Part II: discrete-domain theory. IEEE Trans. Inf. Theory 60(5), 3036–3051 (2014)
Unser, M., Tafti, P.D., Sun, Q.: A unified formulation of Gaussian versus sparse stochastic processes—Part I: continuous-domain theory. IEEE Trans. Inf. Theory 60(3), 1945–1962 (2014)
Acknowledgments
The authors are grateful to R. Dalang for the fruitful discussions we had and V. Uhlmann for her helpful suggestions during the writing. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no 267439.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Hans G. Feichtinger.
Rights and permissions
About this article
Cite this article
Fageot, J., Amini, A. & Unser, M. On the Continuity of Characteristic Functionals and Sparse Stochastic Modeling. J Fourier Anal Appl 20, 1179–1211 (2014). https://doi.org/10.1007/s00041-014-9351-4
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00041-014-9351-4
Keywords
- Characteristic functional
- Generalized stochastic process
- Stochastic differential equation
- Innovation model
- White Lévy noise