International
Tables for Crystallography Volume B Reciprocal space Edited by U. Shmueli © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. B. ch. 1.3, pp. 94-98
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The Fourier transformation plays a central role in the branch of probability theory concerned with the limiting behaviour of sums of large numbers of independent and identically distributed random variables or random vectors. This privileged role is a consequence of the convolution theorem and of the `moment-generating' properties which follow from the exchange between differentiation and multiplication by monomials. When the limit theorems are applied to the calculation of joint probability distributions of structure factors, which are themselves closely related to the Fourier transformation, a remarkable phenomenon occurs, which leads to the saddlepoint approximation and to the maximum-entropy method.
The material in this section is not intended as an introduction to probability theory [for which the reader is referred to Cramér (1946), Petrov (1975) or Bhattacharya & Rao (1976)], but only as an illustration of the role played by the Fourier transformation in certain specific areas which are used in formulating and implementing direct methods of phase determination.
The methods of probability theory just surveyed were applied to various problems formally similar to the crystallographic phase problem [e.g. the `problem of the random walk' of Pearson (1905)] by Rayleigh (1880, 1899, 1905, 1918, 1919) and Kluyver (1906). They became the basis of the statistical theory of communication with the classic papers of Rice (1944, 1945).
The Gram–Charlier and Edgeworth series were introduced into crystallography by Bertaut (1955a,b,c, 1956a) and by Klug (1958), respectively, who showed them to constitute the mathematical basis of numerous formulae derived by Hauptman & Karle (1953). The saddlepoint approximation was introduced by Bricogne (1984) and was shown to be related to variational methods involving the maximization of certain entropy criteria. This connection exhibits most of the properties of the Fourier transform at play simultaneously, and will now be described as a final illustration.
References
Barakat, R. (1974). First-order statistics of combined random sinusoidal waves with applications to laser speckle patterns. Opt. Acta, 21, 903–921.Google ScholarBertaut, E. F. (1955a). La méthode statistique en cristallographie. I. Acta Cryst. 8, 537–543.Google Scholar
Bertaut, E. F. (1955b). La méthode statistique en cristallographie. II. Quelques applications. Acta Cryst. 8, 544–548.Google Scholar
Bertaut, E. F. (1955c). Fonction de répartition: application à l'approache directe des structures. Acta Cryst. 8, 823–832.Google Scholar
Bertaut, E. F. (1956a). Les groupes de translation non primitifs et la méthode statistique. Acta Cryst. 9, 322.Google Scholar
Bhattacharya, R. N. & Rao, R. R. (1976). Normal approximation and asymptotic expansions. New York: John Wiley.Google Scholar
Bleistein, N. & Handelsman, R. A. (1986). Asymptotic expansions of integrals. New York: Dover Publications.Google Scholar
Bricogne, G. (1984). Maximum entropy and the foundations of direct methods. Acta Cryst. A40, 410–445.Google Scholar
Bricogne, G. (1988). A Bayesian statistical theory of the phase problem. I. A multichannel maximum entropy formalism for constructing generalised joint probability distributions of structure factors. Acta Cryst. A44, 517–545.Google Scholar
Bruijn, N. G. de (1970). Asymptotic methods in analysis, 3rd ed. Amsterdam: North-Holland.Google Scholar
Cramér, H. (1946). Mathematical methods of statistics. Princeton University Press.Google Scholar
Daniels, H. E. (1954). Saddlepoint approximation in statistics. Ann. Math. Stat. 25, 631–650.Google Scholar
Fowler, R. H. (1936). Statistical mechanics, 2nd ed. Cambridge University Press.Google Scholar
Hauptman, H. & Karle, J. (1953). Solution of the phase problem. I. The centrosymmetric crystal. ACA Monograph No. 3. Pittsburgh:Polycrystal Book Service.Google Scholar
Hörmander, L. (1973). An introduction to complex analysis in several variables, 2nd ed. Amsterdam: North-Holland.Google Scholar
Jaynes, E. T. (1957). Information theory and statistical mechanics. Phys. Rev. 106, 620–630.Google Scholar
Jaynes, E. T. (1968). Prior probabilities. IEEE Trans. SSC, 4, 227–241.Google Scholar
Jaynes, E. T. (1983). Papers on probability, statistics and statistical physics. Dordrecht: Kluwer Academic Publishers.Google Scholar
Khinchin, A. I. (1949). Mathematical foundations of statistical mechanics. New York: Dover Publications.Google Scholar
Klug, A. (1958). Joint probability distributions of structure factors and the phase problem. Acta Cryst. 11, 515–543.Google Scholar
Kluyver, J. C. (1906). A local probability problem. K. Ned. Akad. Wet. Proc. 8, 341–350.Google Scholar
Pearson, K. (1905). The problem of the random walk. Nature (London), 72, 294, 342.Google Scholar
Petrov, V. V. (1975). Sums of independent random variables. Berlin: Springer-Verlag.Google Scholar
Rayleigh (J. W. Strutt), Lord (1880). On the resultant of a large number of vibrations of the same pitch and arbitrary phase. Philos. Mag. 10, 73–78.Google Scholar
Rayleigh (J. W. Strutt), Lord (1899). On James Bernoulli's theorem in probabilities. Philos. Mag. 47, 246–251.Google Scholar
Rayleigh (J. W. Strutt), Lord (1905). The problem of the random walk. Nature (London), 72, 318.Google Scholar
Rayleigh (J. W. Strutt), Lord (1918). On the light emitted from a random distribution of luminous sources. Philos. Mag. 36, 429–449.Google Scholar
Rayleigh (J. W. Strutt), Lord (1919). On the problem of random flights in one, two or three dimensions. Philos. Mag. 37, 321–347.Google Scholar
Reif, F. (1965). Fundamentals of statistical and thermal physics, Appendix A.6. New York: McGraw-Hill.Google Scholar
Rice, S. O. (1944, 1945). Mathematical analysis of random noise. Bell Syst. Tech. J. 23, 283–332 (parts I and II); 24, 46–156 (parts III and IV). [Reprinted in Selected papers on noise and stochastic processes (1954), edited by N. Wax, pp. 133–294. New York: Dover Publications.]Google Scholar
Shmueli, U. & Weiss, G. H. (1985). Exact joint probability distribution for centrosymmetric structure factors. Derivation and application to the relationship in the space group . Acta Cryst. A41, 401–408.Google Scholar
Shmueli, U. & Weiss, G. H. (1986). Exact joint distribution of , and , and the probability for the positive sign of the triple product in the space group . Acta Cryst. A42, 240–246.Google Scholar
Shmueli, U. & Weiss, G. H. (1987). Exact random-walk models in crystallographic statistics. III. Distributions of for space groups of low symmetry. Acta Cryst. A43, 93–98.Google Scholar
Shmueli, U. & Weiss, G. H. (1988). Exact random-walk models in crystallographic statistics. IV. P.d.f.'s of allowing for atoms in special positions. Acta Cryst. A44, 413–417.Google Scholar
Shmueli, U., Weiss, G. H. & Kiefer, J. E. (1985). Exact random-walk models in crystallographic statistics. II. The bicentric distribution for the space group . Acta Cryst. A41, 55–59.Google Scholar
Shmueli, U., Weiss, G. H., Kiefer, J. E. & Wilson, A. J. C. (1984). Exact random-walk models in crystallographic statistics. I. Space groups and P1. Acta Cryst. A40, 651–660.Google Scholar