Strong interplay between electron-phonon interaction and disorder in low doped systems

The effects of doping on the spectral properties of low doped systems are investigated by means of Coherent Potential Approximation to describe the distributed disorder induced by the impurities and Phonon-Phonon Non-Crossing Approximation to characterize a wide class of electron-phonon interactions which dominate the low-energy spectral features. When disorder and electron-phonon interaction work on comparable energy scales, a strong interplay between them arises, the effect of disorder can no more be described as a mere broadening of the spectral features and the phonon signatures are still visible despite the presence of strong disorder. As a consequence, the disorder-induced metal-insulator transition, is strongly affected by a weak or moderate electron-phonon coupling which is found to stabilize the insulating phase.Comment: New version with improved bibliography and discussio

Le scelte di politica economica in America Latina. Dal periodo ISI al liberismo.

nella presente tesi abbiamo affrontato le principali problematiche economiche dell'America Latina dagli anni '60 a oggi. In Particolare ci siamo soffermati sulla discussione circa l'approccio alle politiche commerciali, concludendo con una valutazione dell'impatto di esportazioni e FDI sulla crescita

Ressenyes

Index de les obres ressenyades: Marco SANTORO, La donna nel Rinascimento meridional

Towards performance governance in the public sector and administrations at international level: three essays

La ricerca nasce dal dibattito a livello internazionale sui Sistemi pubblici manageriali orientati alla “performance” ed affronta il tema attraverso un approccio trasversale a livello sia di policy che di amministrazione nel contesto di entità istituzionali di tipo multilaterale, quali, in particolare, il sistema delle Nazioni Unite. Il focus dell’ analisi è la connessione tra performance e governance, investigando, nello specifico, la possible graduale transizione verso un sistema di “performance governance”, caratterizzato da condivisione di “poteri” e interazioni dinamiche tra i vari stakeholders coinvolti nei processi decisionali e di implementazione degli interventi amministrativi e di policy, affine di incrementarne l’efficacia e l’impatto sulla società. Attraverso una raccolta di tre saggi a cura dello stesso autore della ricerca, si studiano, in particolare, le seguenti realtà istituzionali, avvalendosi di una metodologia qualitativa improntata sul case-study: Servizi pubblici per l’impiego in Europa (capitolo 1 sezione II); Agenzie internazionali – UNESCO (capitolo 2 – sezione II); Organizzazioni mondiali – Sistema ONU (capitolo 3 – sezione II).The study moves from the international debates about performance-based public management systems and its purpose is to answer critical questions at both policy and administrative level through a cross-cutting issues approach (institutional-political, cultural and administrative) in multi-entity settings, such as, in particular, the United Nations System. Our main objective is indeed to explore the connection between (complex and inter-related aspects of) governance and performance and especially if/how the latter may be improved by “manipulating” the former within complex environments, thus designing a possible evolutionary path towards “performance management” and ideally “performance governance” where “power-sharing” and dynamic interactions between the network members are based on defined rules and shared objectives. Through a collection of three essays by the author herself, we therefore explore, through a qualitative methodological approach based on case-study, the functioning of public sector institutions and their societal impacts through improved policies and programs effectiveness across several levels: Employment Services at European level (chapter 1 section II); International Agencies – UNESCO (chapter 2 - section II); World-wide Organisations - United Nation System (chapter 3 – section II)

Out-of-plane seismic response and modelling of unreinforced masonry infill walls

Past and recent earthquakes showed that the seismic performance of buildings is strongly influenced by the presence and contribution of unreinforced masonry (URM) infills, which are usually considered as non-structural elements. Such enclosures are used – especially in Mediterranean countries – to provide buildings with thermic, visual and acoustic insulation. On one hand, URM infills can stand significant lateral loads and, so, they contribute to the lateral strength capacity of structures. In addition, they are provided with a high in-plane stiffness. For this reason, the assessment of a construction modelled as bare frame can yield to a significant underestimation of its lateral strength and stiffness. On the other hand, it is well-known that the high force demand that URM enclosures attract and then transfer to the confining elements can yield to unexpected failures of structural members designed without accounting for infills’ presence. For example, Reinforced Concrete (RC) columns (and beams, potentially) not designed addressing seismic and capacity design provisions sometimes exhibit brittle failures during strong earthquakes due to the so-called “frame-infill interaction”, i.e., due to the shear forces transferred by infills and not considered in the design. Moreover, the absence of infills at a certain storey of a building (typically, the first) produces a non-negligible stiffness variation of the structure lateral stiffness along its height, leading, in this way, to potential peaks of inelastic demand at that storey yielding to a sidesway collapse due to a soft-storey mechanism. In addition, infills’ damaging due to IP actions and their repair or refurbishment produces most of the financial losses consequent to earthquakes. In other words, neglecting infills’ presence and their contribution to the seismic response of structures can be both conservative and unconservative. For these reasons, the interest in the characterization of the seismic response of URM infills has significantly grown in the engineering and research community in the last decades. It should be noted that these bi-dimensional non-structural elements are subjected to the seismic action both in the in-plane (IP) and in the out-of-plane (OOP) direction. The expulsion or overturning from the confining frame due to OOP actions of URM infills is potentially highly detrimental for human life safety and amplifies the economic losses consequent to earthquakes. The OOP collapse of URM infills is promoted by the damage due to IP actions, which can reduce their OOP strength, stiffness and displacement capacity. This phenomenon is called IP/OOP interaction. This PhD thesis is dedicated to the characterization and modelling of the OOP behaviour of URM infills and to the study of the effects of the IP/OOP interaction both at the level of the single (non-structural) component and at the level of the infilled structure seismic performance. Chapter I is dedicated to the existing literature concerning this issue and investigating the definition of the OOP strength, stiffness and displacement capacity of URM infills. In addition, existing formulation for the prediction and reproduction of the IP/OOP interaction effects are addressed. Finally, existing URM infills’ modelling strategies accounting for their OOP behaviour and for the IP/OOP interaction effects are described in detail. Chapter II constitute the second part of the previous literature recall, as it is dedicated to a detailed description of the experimental tests carried out in the past to investigate the OOP behaviour of URM infills and the IP/OOP interaction effects. It is observed that the experimental database allowing evaluating the effectiveness and robustness of literature formulations and models described in Chapter I is extremely poor. For this reason, a comprehensive and extended experimental program has been carried out at the Department of Structures for Engineering and Architecture of University of Naples Federico II. The experimental program main aim is the characterization of the effects of the panel height-to-thickness slenderness ratio, of the boundary conditions at edges and of the IP/OOP interaction on the OOP strength, stiffness and displacement capacity of URM infills. A total of fifteen tests has been carried out to enrich the available experimental database. Chapter III is dedicated to a detailed description of the experimental program and of its results. In Chapter IV, the experimental database collected in Chapter II and III is analysed and discussed, in order to compare the prediction of literature formulations and models aimed at assessing the OOP response of URM infills and/or its significant parameters, such as the force at first macro-cracking and at maximum, as well as their secant stiffness at the first macro-cracking and at maximum and the displacement capacity/ductility. The predicting capacity of the available IP/OOP interaction models is assessed, too. This comparison is aimed at evaluating the effectiveness of the available models for the prediction of the OOP response of both IP-undamaged and IP-damaged URM infills. Based on the results of this comparison, original and mechanical based proposals are described for a robust and effective modelling of URM infills’ OOP response. In addition, empirical formulation for the prediction of the IP/OOP interaction are proposed. With Chapter IV, the characterization of the OOP behaviour of the single panel, which is the first part of this thesis, is completed. Chapter V is dedicated to a simple state-of-the-art concerning the current provisions given by international technical codes and standards for the assessment of URM infills safety with respect to OOP seismic demands. More specifically, demand and capacity models provided by codes are described and discussed. This is preliminary to the assessment of the seismic performance of RC buildings accounting for the OOP response of infills and for the IP/OOP interaction effects, which is the second part of this thesis. To this aim, a set of sixteen case-study buildings has been designed according to Eurocodes’ provisions. The case-study buildings are described and commented in detail in Chapter VI. The case-study buildings are different for the number of storeys, which is equal to 2, 4, 6 or 8, and for the design peak ground acceleration (PGA) at Life Safety Limit State. In Chapter VII, the case-study buildings described in the previous section are used to assess the PGA at the first OOP collapse of different infill layouts in a non-linear static framework by using both a simplified “Designer (code-based) Approach” and a refined “Reference Approach”. Only the least accounts, in evaluating the OOP force demand and capacity of infills, for the structural nonlinearity as well as for the IP/OOP interaction effects. The dependence of such the PGA capacity with respect to the first OOP collapse on the number of storeys and on the design PGA is discussed. In addition, the PGA at the first OOP collapse is compared with the design PGA of the case-study buildings as well as to the PGA corresponding to their conventional structural collapse. It is shown that weak infills in mid- and high-rise buildings can collapse for OOP actions and due to the IP/OOP interaction effects at PGA demand lower than the PGA at structural collapse or even than the design PGA. In addition, simplified criteria to evaluate, based on infills geometric and mechanical properties, if the OOP safety check is necessary or not are presented. In Chapter VIII, the seismic performance of the case-study buildings accounting and not accounting for the IP/OOP interaction effects on URM infills is assessed by means of non-linear incremental dynamic analysis. Also in this case, the overall capacity of buildings with respect to the first OOP collapse is investigated. In addition, the OOP behaviour factor and effective stiffness of URM infills accounting for the IP/OOP interaction effects is evaluated. Such values can be used for a simplified OOP safety check of URM infills in a linear elastic framework. In the appendix section, some theoretical considerations and experimental data supporting the discussions above proposed are reported in detail

The influence of productivity gains, their distribution, and market structure on economic growth in a Sraffian Supermultiplier model. Short-, medium-, long-term trends and secular tendencies. an analysis performed through a multisectoral macroeconomic SFC-AB model

Lo scopo di questo lavoro è di indagare le proprietà del modello del supermoltiplicatore sraffiano in cui il cambiamento tecnologico e la domanda autonoma, proveniente dal settore pubblico, influenzano congiuntamente le dinamiche macroeconomiche. Il tasso di crescita dell'economia è determinato dal percorso di crescita della produttività, che libera la forza lavoro da impiegare nella produzione di beni alternativi, e dal settore pubblico, che, se non è disposto ad accettare un'elevata disoccupazione, deve aumentare le proprie spese per generare la domanda necessaria per il raggiungimento crescita macroeconomica. Premesso che il cambiamento tecnologico è influenzato dal livello di vendita (dovuto alle possibilità che si aprono in termini di divisione del lavoro) -a tutti i livelli (macro, meso e micro), in contrasto con la maggior parte dei modelli di supermoltiplicatori, il tasso di crescita a lungo termine del nostro modello risente anche della distribuzione del reddito (sia funzionale che personale) che modella il livello della domanda totale e la sua composizione tra i settori, e dalla struttura del mercato che determina la ripartizione della produzione tra le imprese. Ai fini della nostra ricerca, abbiamo sviluppato un Agente macroeconomico multisettoriale basato - Modello coerente con lo Stock Flow (AB-SFC). Il modello si basa su un quadro teorico che rappresenta un'economia monetaria di produzione (es. Graziani, Lavoie) dove il principio della domanda effettiva determina il livello di produzione, mentre l'innovazione è caratterizzata da un tipico processo schumpeteriano di creazione e distruzione. La distribuzione del reddito funzionale è determinata come nella teoria classica ed è il risultato della lotta tra capitalisti e classe operaia. In particolare, il markup fissato dalle imprese sul normale costo unitario di produzione determina il normale saggio di profitto. Il denaro è endogeno ed è immesso nel sistema dalle banche che concedono prestiti alle imprese per finanziare investimenti o salari di anticipazione, e dalla spesa pubblica finanziata con l'emissione di titoli pubblici. Nel secondo capitolo viene presa una prospettiva a breve termine e l'impatto della performance della macroeconomia annuale viene analizzato sulla traiettoria a lungo termine dell'economia. In primo luogo, dimostriamo che il processo di innovazione è una condizione necessaria ma non sufficiente per la crescita economica (e potenziale fonte di instabilità economica) e che, per raggiungere la crescita macroeconomica, è necessario un settore pubblico pratico (che aumenta il proprio debito ogni volta che si verifica un aumento di produttività e stabilizza l'economia). Quindi, indaghiamo come diverse appropriazioni dei guadagni di produttività (e, di conseguenza, diverse configurazioni distributive) influenzano l'andamento futuro della produttività (e, di conseguenza, il tasso di crescita di lungo periodo dell’economia) attraverso le variazioni del livello di volume aggregato e la loro allocazione tra i settori. Nel terzo capitolo, l'attenzione si sposta sulle dinamiche a lunghissimo termine del sistema capitalista e la connessione tra processo di innovazione, concentrazione del mercato e disparità di reddito. Iniziamo a esplorare quali possono essere le tendenze secolari che derivano dalla crescita economica e le forze di cambiamento strutturale, che sono naturalmente dietro di essa. Nello specifico, mostriamo come la riduzione dell'occupazione, a livello settoriale, arriva logicamente con l'aumento del livello di produttività del lavoro e la preferenza dei consumatori per la varietà può avere ripercussioni in termini di struttura del mercato e distribuzione personale. Poi vengono analizzate le conseguenze sulla crescita economica della potenziale combinazione della struttura del mercato e la disuguaglianza di reddito, che può verificarsi in economie in fase di crescita e di cambiamenti strutturali.The purpose of this work is to investigate the properties of the Sraffian supermultiplier model in which technological change and autonomous demand, coming from the public sector, jointly affect macroeconomic dynamics. The growth rate of the economy is determined by the path of productivity growth, which frees up the labour force to be used in the production of alternative goods, and by the public sector, which, if unwilling to accept high unemployment, must increase its expenditures in order to generate the necessary demand for achieving macroeconomic growth. Given the assumption that the technological change is affected by the sales level (due to the possibilities it opens in terms of labor division) -at all layers (macro, meso and micro), in contrast to the majority of supermultiplier models, the long-run growth rate of our model is also affected by the income distribution (both functional and personal) that shapes the level of total demand and its composition across sectors, and by the market structure that determines the production allocation among firms. For the purpose of our research, we have developed a multi-sectoral macroeconomic Agent based - Stock Flow consistent model (AB-SFC). The model is grounded on a theoretical framework representing a monetary economy of production (e.g., Graziani, Lavoie) where the principle of effective demand determines the level of output, while innovation is characterized by a typical Schumpeterian process of creation and destruction. The functional income distribution is determined as in the classical theory and it is the resultant of the struggle between capitalists and working class. In particular, the markup fixed by firms on normal unit-cost of production determines the normal rate of profit. Money is endogenous and it is injected into the system by banks which grant loans to firms to finance investments or wages anticipation, and by government expenditure financed by issuing public bonds. In the second chapter, a short-term perspective is taken and the impact of annual macroeconomic performance on the long-term trajectory of the economy is analysed. First, we demonstrate that process innovation is a necessary but insufficient condition for economic growth (and a potential source of economic instability) and that, to achieve macroeconomic growth, a hands-on public sector is required (that increase its debt every time an increase in productivity occurs and stabilises the economy). Then, we investigate how different appropriations of the productivity gains (and, consequently, different distribution configurations) affect the future trend of productivity (and, consequently, the long-run growth rate of the economy) via changes in the aggregate volume level and their allocation between sectors. In the third chapter, the focus moves to the extremely long-term dynamics of the capitalist system and the connection between process innovation, market concentration, and income inequality. We start exploring which can be the secular trends that come with economic growth and the structural changes forces, which are naturally behind it. Specifically, we show how the reduction of the employment, at the sectoral level, which logically comes with increasing level of labor productivity and consumers preference for variety can have repercussions in terms of market structure and personal distribution. Then, the economic growth consequences of the potential combination of market structure and income inequality, which may occur in economies experiencing growth and structural changes, are then analysed

Testing a quintessence model with CMBR peaks locations

We show that a model of quintessence with exponential potential, which allows to obtain general exact solutions, can generate location of CMBR peaks which are fully compatible with present observational data

CPT and QM tests using kaon interferometry

The neutral kaon system offers a unique possibility to perform fundamental tests of CPT invariance, as well as of the basic principles of quantum mechanics. The most recent and significant limits on CPT violation are reviewed, including the ones related to possible decoherence mechanisms or Lorentz symmetry breaking, which might be induced by quantum gravity. The experimental results show no deviations from the expectations of quantum mechanics and CPT symmetry, while the accuracy in some cases reaches the interesting Planck scale region. Finally, prospects for this kind of experimental studies at the upgraded DAFNE e+e- collider at Frascati are briefly discussed.Comment: talk at Heavy Quarks and Leptons, Melbourne, 200