Magnetic polarons in weakly doped high-Tc superconductors

We consider a spin Hamiltonian describing $d$-$d$ exchange interactions between localized spins $d$ of a finite antiferromagnet as well as $p$-$d$ interactions between a conducting hole ($p$) and localized spins. The spin Hamiltonian is solved numerically with use of Lanczos method of diagonalization. We conclude that $p$-$d$ exchange interaction leads to localization of magnetic polarons. Quantum fluctuations of the antiferromagnet strengthen this effect and make the formation of polarons localized in one site possible even for weak $p$-$d$ coupling. Total energy calculations, including the kinetic energy, do not change essentially the phase diagram of magnetic polarons formation. For parameters reasonable for high-$T_c$ superconductors either a polaron localized on one lattice cell or a small ferron can form. For reasonable values of the dielectric function and $p$-$d$ coupling, the contributions of magnetic and phonon terms in the formation of a polaron in weakly doped high-$T_c$ materials are comparable.Comment: revised, revtex-4, 12 pages 8 eps figure

Innovazione ed incompetenza nella giustizia

Prendendo spunto dagli esperimenti di adozione della videoregistrazione nel processo penale intrapresi negli anni '90, il saggio illustra e discute gli aspetti pi\uf9 critici del sistema giudiziario italiano, spiegando perch\ue8 la forte impronta burocratica dell'amministrazione della giustizia \ue8 fonte di incompetenza organizzativa, rendendo difficile l'innovazione

Building institutional interoperability for European Civil Procedure: The case of Money Claim OnLine in England and Wales

The general aim of the project is to contribute to the development of e-justice to foster civil justice services at the European level. Overall, it is to be regarded as a further step of a broad research endeavor that IRSIG-CNR has been carrying in recent years to develop a large body of empirical knowledge about the functioning of e-justice systems in EU and to identify key issues affecting the development of e-justice in different countries. The project is designed to assess the legal, institutional, organizational and technical conditions in which e-justice can successfully support and handle small claims in trans-border cases as indicated in Priority 3.1 of the call, paying particular attention to the normative framework recently developed at EU level (the European payment orders, the Regulations on small claims No 861/2007 No 1896/2006 and the Directive on EU payment 2008/52/EC on mediation). Specifically the project focuses on interoperability in the provision of electronic systems for handling small claims online across national borders in the EU. It aims at configuring and comparing different models for providing e-justice. The project purports to analyze the compatibilities and the different types of interoperability between the national systems. That entails not only the study of technical standards, but also the different organizational arrangements and the juridical base of different national systems. The basic question the project intends to answer is: What needs to be done for the national justice systems to become more integrated and capable of \u2018talking\u2019 to one another in the treatment of small claims and payment orders online? Should technical, functional and legal interfaces be designed or should a new electronic jurisdiction be created at the European level encompassing the national systems

Portraits of Claudio: the butterfly, the dragon and the marmot

a personal memory of the late Claudio Ciborr

Per Claudio Ciborra, politropos

un ricordo personale di Claudio Ciborr

Self-destructive dynamics in large-scale technochange and some ways of counteracting it

Purpose - Seeks to raise the question of why large-scale technochange is difficult and often failure-prone and to attempt to answer this question by viewing technochange as an instance of institutional change and design in which self-destructive mechanisms are inherently embedded. Design/methodology/approach - In order to explore the complex institutional dynamics of large-scale technochange the paper uses the exploration/exploitation framework originally developed by March and extended by Lanzara to the study of institution-building processes in the political domain. The argument is that problems in implementing large-scale technochange stem from learning dilemmas in the inter-temporal and inter-group allocation of material and cognitive resources. The paper uses a case of large-scale technology in a major US university system to illustrate the institutional perspective on technochange. Findings - It is argued and illustrated that the development and redesign of large-scale information systems involve both the exploration of alternative institutional arrangements and the exploitation of pre-existing ones, such that a delicate balance must be struck to overcome incoherences and dilemmas between the two activities. Research limitations/implications - The proposed framework to understand large-scale technochange is not examined empirically. The illustration of the framework relies on a single large-scale system project of a non-profit organization in the USA. Further empirical work and comparative research on multiple cases are needed. Practical implications - The paper discusses some sources of the failures of large-scale technochange and offers three interrelated mechanisms to counteract such failure sources, namely focal points, increasing returns, and bricolage. These counteracting mechanisms may help organizations to effectively deal with the dilemmas of exploration and exploitation in technochange. Originality/value - This paper fills the gap in understanding the nature of large-scale technochange, providing an explanation of why it is difficult and failure-prone and offering some modest proposals for intervention in large-scale system projects