## Abstract snark

The abstracts for these two papers (one a classic in robust control theory, the other in mathematical physics) are almost Zen in their simplicity and perfection:

J. C. Doyle, “Guaranteed margins for LQG regulators,” *IEEE Transactions on Automatic Control*, vol. 23, no. 4, pp. 756-757, 1978

Abstract:There are none.

J. E. Avron, L. Sadun, J. Segert and B. Simon, “Chern numbers, quaternions, and Berry’s phases

in Fermi systems,” *Communications in Mathematical Physics*, vol. 124, pp. 595-627, 1989

Abstract:Yes, but some parts are reasonably concrete.

P.S. (More or less) regular blogging to resume in 3, 2, 1 … .

## The lost art of writing

From the opening paragraph of Herman Chernoff‘s unpublished 1963 memo “Backward induction in dynamic programming” (thanks to Armand Makowski for a scanned copy):

The solution of finite sequence dynamic programming problems involve a backward induction argument, the foundations of which are generally understood hazily. The purpose of this memo is to add some clarification which may be slightly redundant and whose urgency may be something less than vital.

Alas, nobody writes like that anymore.

## In Soviet Russia, the sigma-field conditions on you

Quote of the day, from *Asymptotics in Statistics: Some Basic Concepts* by Lucien Le Cam and Grace Yang (emphasis mine):

The idea of developing statistical procedures that minimize an expected loss goes back to Laplace … [and] reappears in papers of Edgeworth. According to Neyman in his Lectures and Conferences: “After Edgeworth, the idea of the loss function was lost from sight for more than two decades …” It was truly revived only by the appearance on the statistical scene of Wald. Wald’s books

Sequential AnalysisandStatistical Decision Functionsare based on that very idea of describing experiments by families of probability measures either on one given -field or on sequence of -fields to be chosen by the statistician. The idea seems logical enough if one is used to it. However, there is a paper by Fisher where he seems to express the opinion thatsuch concepts are misleading and good enough only for Russian or American engineers.

Follow the link to Fisher’s paper for more curmudgeonly remarks about “Russians” and their “five-year plans.”

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