Asymptotic and effective coarsening exponents in surface growth models

We consider a class of unstable surface growth models, z_t = -\partial_x J, developing a mound structure of size lambda and displaying a perpetual coarsening process, i.e. an endless increase in time of lambda. The coarsening exponents n, defined by the growth law of the mound size lambda with time, lambda=t^n, were previously found by numerical integration of the growth equations [A. Torcini and P. Politi, Eur. Phys. J. B 25, 519 (2002)]. Recent analytical work now allows to interpret such findings as finite time effective exponents. The asymptotic exponents are shown to appear at so large time that cannot be reached by direct integration of the growth equations. The reason for the appearance of effective exponents is clearly identified.Comment: 6 pages. Several parts and conclusions have been rewritten. (Addendum to the article that can be found in http://www.arxiv.org/abs/cond-mat/0110058

Relaxation and coarsening of weakly-interacting breathers in a simplified DNLS chain

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Quantifying the Dynamical Complexity of Chaotic Time Series

Acknowledgements The author wishes to acknowledge G. Giacomelli, M. Mulansky, and L. Ricci for early discussions.Peer reviewedPublisher PD

Specialisation, Interdisciplinarity, and Incommensurability

Incommensurability may be regarded as driving specialisation, on the one hand, and as posing some problems to interdisciplinarity, on the other hand. It may be argued, however, that incommensurability plays no role in either specialisation or interdisciplinarity. Scientific specialties could be defined as simply 'different' (that is, about different things), rather than 'incommensurable' (that is, competing for the explanation of the same phenomena). Interdisciplinarity could be viewed as the co- ordinated effort of scientists possessing complemetary and interlocking skills, and not as the overcoming of some sort of incommensurable divide. This article provides a comprehensive evaluative examination of the relations between specialisation, interdisciplinarity, and incommensurability. Its aim is to defend the relevance of incommensurability to both specialisation and interdisciplinarity. At the same time, it aims at correcting the tendency, common among many philosophers, to regard incommensurability in a restrictive manner - such as, for example, as an almost purely semantic issu

Coarsening dynamics at unstable crystal surfaces

In this paper we focus on crystal surfaces led out of equilibrium by a growth or erosion process. As a consequence of that the surface may undergo morphological instabilities and develop a distinct structure: ondulations, mounds or pyramids, bunches of steps, ripples. The typical size of the emergent pattern may be fixed or it may increase in time through a coarsening process which in turn may last forever or it may be interrupted at some relevant length scale. We study dynamics in three different cases, stressing the main physical ingredients and the main features of coarsening: a kinetic instability, an energetic instability, and an athermal instability.Comment: 12 pages. Several minor changes. To appear in a Comptes Rendus Physique special issue on "Coarsening Dynamics", see https://sites.google.com/site/ppoliti/crp-special-issu

The effects of the generalized use of iodized salt on occupational patterns in Switzerland

This paper examines the impact of salt iodization in Switzerland in the 1920s and 1930s on occupational patterns of cohorts born after the intervention. The generalized use of iodized salt successfully combatted iodine deficiency disorders, which were previously endemic in some areas of Switzerland. The most important effect of universal prophylaxis by means of iodized salt was the eradication of mental retardation inflicted in utero by lack of iodine. This paper looks for evidence of increased cognitive ability of those treated with iodine in utero by examining the occupational choice and characteristics of occupations chosen by cohorts born after the intervention. By exploiting variation in pre-existing conditions and in the timing of the intervention, I find that cohorts born in previously highly-deficient areas after the introduction of iodized salt self-selected into higher-paying occupations. I also find that the characteristics of occupations in those areas changed, and that cohorts born after the intervention engaged to a higher degree in occupations with higher cognitive demands, whereas they opted out of physical-labor-intensive occupations

Single-domain versus two-domain configuration in thin ferromagnetic prisms

Thin ferromagnetic elements in the form of rectangular prisms are theoretically investigated in order to study the transition from single-domain to two-domain state, with changing the in-plane aspect ratio p. We address two main questions: first, how general is the transition; second, how the critical value p_c depends on the physical parameters. We use two complementary methods: discrete-lattice calculations and a micromagnetic continuum approach. Ultrathin films do not appear to split in two domains. Instead, thicker films may undergo the above transition. We have used the continuum approach to analyze recent Magnetic Force Microscopy observations in 30 nm-thick patterned Permalloy elements, finding a good agreement for p_c.Comment: 22 pages, 5 figure