Hammersley: Crystals

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“We deal with atoms and bonds: a bond is a (perhaps directed) path between two atoms. An n-stepped walk is an ordered connected path along n consecutive bonds, each step being in the permitted direction of a bond (if the bond in question is directed) and starting from the atom reached by the previous step (if any). Wn(A) denotes a typical n-stepped walk starting from an atom A. A walk is self-avoiding if it visits no atom more than once. Sn(A) denotes a self-avoiding Wn(A). Two walks are distinct if they do not utilize the same set of bonds, with due regard to order. fA(n, r) denotes the number of distinct Wn(A), each of which can be broken into r or fewer self-avoiding subwalks. In particular we write fA(n) =fA(n, 1) for the number of distinct Sn(A). Two atoms A and B are outlike if fA(n) = fB{n) for all n. An outlike class is a class of pairwise outlike atoms. A crystal is an infinite set of atoms and bonds satisfying the three postulates” (p. 642) #Hammersley #atom #bond #walk #crystal

Hammersley, John M., Percolation processes. II. The Connective Constant, in: Mathematical Proceedings of the Cambridge Philosophical Society 53 (1957), 642–645.

Newman: Networks

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“The study of networks, in the form of mathematical graph theory, is one of the fundamental pillars of discrete mathematics.” (p. 2) #Newman #networks #GraphTheory #mathematics

Newman, Mark E. J., The Structure and Function of Complex Networks, in: SIAM Review 45 (2003), 167–256.

Grimmett: Percolation

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“Suppose we immerse a large porous stone in a bucket of water. What is the probability that the centre of the stone is wetted? In formulating a simple stochastic model for such a situation, Broadbent and Hammersley (1957) gave birth to the ‚percolation model‘.” (p. 1) #Grimmett #Broadbent #Hammersley #percolation

Grimmett, Geoffrey R., Percolation. With 76 Illustrations. New York: Springer 1989. 296 S., ISBN 978-1-4757-4210-7.

Wildgen: La brisure de la symétrie

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“La brisure de la symétrie est en même temps une entité d’information discrète, car les petits changements quantitatifs n’avaient pas d’effet qualitatif ; après la brisure de symétrie l’observateur a gagné une information nouvelle sur son objet. […] Dans un article de 1992, René Thom revient au sujet de la brisure de symétrie comme source d’information.” (p. 4sq.) #Wildgen #Thom #brisure #information

Wildgen, Wolfgang, Le problème du continu/discontinu dans la sémiophysique de René Thom et l’origine du langage. The Distinction between Continuousness and Discontinuousness in René Thom’s „Semiophysics“ and the Origin of Language, in: Cahiers de praxématique 42 (2004), 1–16.

Chen: Phase Transition

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„One of the most fundamental characteristics of a phase transition is its order, i.e., whether the macroscopic quantity it affects changes continuously or discontinuously at the transition point. Continuous transitions are called ’second-order‘ and include many magnetization phenomena, whereas discontinuous transitions are called ‚first-order,‘ an example of which is the discontinuous drop in entropy when liquid water turns into solid ice at zero degrees.“ (p. 3) #Chen #PhaseTransition

Chen, Wei, Explosive Percolation in Random Networks. Berlin/Heidelberg: Springer 2014. 63 S.