Crises and collective socio-economic phenomena: simple models and challenges

Financial and economic history is strewn with bubbles and crashes, booms and busts, crises and upheavals of all sorts. Understanding the origin of these events is arguably one of the most important problems in economic theory. In this paper, we review recent efforts to include heterogeneities and interactions in models of decision. We argue that the Random Field Ising model (RFIM) indeed provides a unifying framework to account for many collective socio-economic phenomena that lead to sudden ruptures and crises. We discuss different models that can capture potentially destabilising self-referential feedback loops, induced either by herding, i.e. reference to peers, or trending, i.e. reference to the past, and account for some of the phenomenology missing in the standard models. We discuss some empirically testable predictions of these models, for example robust signatures of RFIM-like herding effects, or the logarithmic decay of spatial correlations of voting patterns. One of the most striking result, inspired by statistical physics methods, is that Adam Smith's invisible hand can badly fail at solving simple coordination problems. We also insist on the issue of time-scales, that can be extremely long in some cases, and prevent socially optimal equilibria to be reached. As a theoretical challenge, the study of so-called "detailed-balance" violating decision rules is needed to decide whether conclusions based on current models (that all assume detailed-balance) are indeed robust and generic.Comment: Review paper accepted for a special issue of J Stat Phys; several minor improvements along reviewers' comment

Superconducting YBa2Cu3O7-δ thin films on GaAs with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on GaAs with conducting indium-tin-oxide (ITO) buffer layers. Superconducting onset is about 92 K with zero resistance at 60 K. ITO buffer layers usually form Schottky-like barriers on GaAs. The YBCO film and ITO buffer layer, grown by ion beam sputter codeposition, are textured and polycrystalline with a combined room-temperatures resistivity of about 1 mΩ c

In situ growth of superconducting YBa2Cu3O7-δ thin films on Si with conducting indium-tin-oxide buffer layers

Superconducting YBa2Cu3O7-δ (YBCO) thin films have been grown in situ on Si with conducting indium-tin-oxide (ITO) buffer layers. ITO allows YBCO to be electrically connected to the underlying Si substrate. Both the YBCO film and ITO buffer layer, grown by ion beam sputtering, are textured and polycrystalline with a combined room-temperature resistivity of about 2 mΩ cm. Superconducting onsets are 92 K with zero resistance at 68

Computational prediction of microRNA genes in silkworm genome

MicroRNAs (miRNAs) constitute a novel, extensive class of small RNAs (~21 nucleotides), and play important gene-regulation roles during growth and development in various organisms. Here we conducted a homology search to identify homologs of previously validated miRNAs from silkworm genome. We identified 24 potential miRNA genes, and gave each of them a name according to the common criteria. Interestingly, we found that a great number of newly identified miRNAs were conserved in silkworm and Drosophila, and family alignment revealed that miRNA families might possess single nucleotide polymorphisms. miRNA gene clusters and possible functions of complement miRNA pairs are discussed

In-Situ and Real-Time Analysis of the Formation of Strains and Microstructure Defects during Solidification of Al-3.5 Wt Pct Ni Alloys

International audienceAlloy solidification was investigated in situ and real time by using a unique experimental setup developed at the European Synchrotron Radiation Facility (ESRF) combining both synchrotron X-ray radiography and topography. Although synchrotron X-ray radiography enables the investigation of the solid-liquid interface of metallic alloys, white-beam synchrotron X-ray topography enables the investigation of the formation of strains and defects formation in the growing solid microstructure. In this article, we present results obtained during directional solidification experiments performed with Al-3.5 wt pct Ni samples. First, the initial state after thermal stabilization is characterized. Next, the interface morphological instability and the transition to the columnar growth regime are thoroughly investigated. Topography observation shows that several parts of each dendrite become disoriented while the microstructure is developing. Disorientations are quantified and the aluminum yield stress at the melting point is estimated from the bending of secondary arms. Last, coupled growth of eutectic and dendrites settles with the formation of the eutectic phase. The eutectic grains grow strained and the dendrites concomitantly undergo additional stress