Collective effects for the LHC injectors: non-ultrarelativistic approaches

The upgrade of the CERN accelerator complex has been planned in order to further increase the LHC performances in exploring new physics frontiers. One of the main limitations to the upgrade is represented by the collective instabilities. These are intensity dependent phenomena triggered by electromagnetic fields excited by the interaction of the beam with its surrounding. These fields are represented via wake fields in time domain or impedances in frequency domain. Impedances are usually studied assuming ultrarelativistic bunches while we mainly explored low and medium energy regimes in the LHC injector chain. In a non-ultrarelativistic framework we carried out a complete study of the impedance structure of the PSB which accelerates proton bunches up to 1.4 GeV. We measured the imaginary part of the impedance which creates betatron tune shift. We introduced a parabolic bunch model which together with dedicated measurements allowed us to point to the resistive wall impedance as the source of one of the main PSB instability. These results are particularly useful for the design of efficient transverse instability dampers. We developed a macroparticle code to study the effect of the space charge on intensity dependent instabilities. Carrying out the analysis of the bunch modes we proved that the damping effects caused by the space charge, which has been modelled with semi-analytical method and using symplectic high order schemes, can increase the bunch intensity threshold. Numerical libraries have been also developed in order to study, via numerical simulations of the bunches, the impedance of the whole CERN accelerator complex. On a different note, the experiment CNGS at CERN, requires high-intensity beams. We calculated the interpolating Hamiltonian of the beam for highly non-linear lattices. These calculations provide the ground for theoretical and numerical studies aiming to improve the CNGS beam extraction from the PS to the SPS.

On the Design of a Boolean-network Robot Swarm: Collective Recognition of Ground Patterns.

Uno dei principali ambiti di ricerca dell’intelligenza artificiale concerne la realizzazione di agenti (in particolare, robot) in grado di aiutare o sostituire l’uomo nell’esecuzione di determinate attività. A tal fine, è possibile procedere seguendo due diversi metodi di progettazione: la progettazione manuale e la progettazione automatica. Quest’ultima può essere preferita alla prima nei contesti in cui occorra tenere in considerazione requisiti quali flessibilità e adattamento, spesso essenziali per lo svolgimento di compiti non banali in contesti reali. La progettazione automatica prende in considerazione un modello col quale rappresentare il comportamento dell’agente e una tecnica di ricerca (oppure di apprendimento) che iterativamente modifica il modello al fine di renderlo il più adatto possibile al compito in esame. In questo lavoro, il modello utilizzato per la rappresentazione del comportamento del robot è una rete booleana (Boolean network o Kauffman network). La scelta di tale modello deriva dal fatto che possiede una semplice struttura che rende agevolmente studiabili le dinamiche tuttavia complesse che si manifestano al suo interno. Inoltre, la letteratura recente mostra che i modelli a rete, quali ad esempio le reti neuronali artificiali, si sono dimostrati efficaci nella programmazione di robot. La metodologia per l’evoluzione di tale modello riguarda l’uso di tecniche di ricerca meta-euristiche in grado di trovare buone soluzioni in tempi contenuti, nonostante i grandi spazi di ricerca. Lavori precedenti hanno gia dimostrato l’applicabilità e investigato la metodologia su un singolo robot. Lo scopo di questo lavoro è quello di fornire prova di principio relativa a un insieme di robot, aprendo nuove strade per la progettazione in swarm robotics. In questo scenario, semplici agenti autonomi, interagendo fra loro, portano all’emergere di un comportamento coordinato adempiendo a task impossibili per la singola unità. Questo lavoro fornisce utili ed interessanti opportunità anche per lo studio delle interazioni fra reti booleane. Infatti, ogni robot è controllato da una rete booleana che determina l’output in funzione della propria configurazione interna ma anche dagli input ricevuti dai robot vicini. In questo lavoro definiamo un task in cui lo swarm deve discriminare due diversi pattern sul pavimento dell’arena utilizzando solo informazioni scambiate localmente. Dopo una prima serie di esperimenti preliminari che hanno permesso di identificare i parametri e il migliore algoritmo di ricerca, abbiamo semplificato l’istanza del problema per meglio investigare i criteri che possono influire sulle prestazioni. E’ stata così identificata una particolare combinazione di informazione che, scambiata localmente fra robot, porta al miglioramento delle prestazioni. L’ipotesi è stata confermata applicando successivamente questo risultato ad un’istanza più difficile del problema. Il lavoro si conclude suggerendo nuovi strumenti per lo studio dei fenomeni emergenti in contesti in cui le reti booleane interagiscono fra loro.

'Defending the rights'. An integrated model of collective action for "public water" in Italy

In many communities, supplying water for the people is a huge task and the fact that this essential service can be carried out by the private sector respecting the right to water, is a debated issue. This dissertation investigates the mechanisms through which a 'perceived rights violation' - which represents a specific form of perceived injustice which derives from the violation of absolute moral principles – can promote collective action. Indeed, literature on morality and collective action suggests that even if many people apparently sustain high moral principles (like human rights), only a minority decides to act in order to defend them. Taking advantage of the political situation in Italy, and the recent mobilization for "public water" we hypothesized that, because of its "sacred value", the perceived violation of the right to water facilitates identification with the social movement and activism. Through five studies adopting qualitative and quantitative methods, we confirmed our hypotheses demonstrating that the perceived violation of the right to water can sustain activism and it can influence vote intentions at the referendum for 'public water'. This path to collective action coexists with other 'classical' predictors of collective action, like instrumental factors (personal advantages, efficacy beliefs) and anger. The perceived rights violation can derive both from personal values (i.e. universalism) and external factors (i.e. a mobilization campaign). Furthermore, we demonstrated that it is possible to enhance the perceived violation of the right to water and anger through a specifically designed communication campaign. The final chapter summarizes the main findings and discusses the results, suggesting some innovative line of research for collective action literature.

Dalla "postmémoire" alla scrittura dell'oblio nell'opera di Sylvie Germain

La tesi intitolata "Dalla «postmémoire» alla scrittura dell’oblio nell’opera di Sylvie Germain" si pone l’obbiettivo di analizzare l’opera della scrittrice francese contemporanea Sylvie Germain alla luce di alcune elaborazioni teoriche sulla dialettica memoria/oblio. Basandoci sulle principali teorie-guida relative alla «memoria culturale» teorizzate da Maurice Halbwachs,Pierre Nora,Tzvetan Todorov,Paul Ricoeur e Aleida Assmann,la nostra analisi si è successivamente concentrata sugli studi condotti attorno al concetto di «postmemory» elaborato dalla studiosa americana Marianne Hirsch. Scopo di questa prospettiva critica è quello di leggere l'opera germainiana come espressione di una «affiliative postmemory», risultato della connessione generazionale di coloro che non hanno vissuto direttamente un trauma con la «literal second generation». Attraverso un approccio interdisciplinare che ha coinvolto gli studi sulla memoria culturale in rapporto alla questione del gender, si è inoltre evidenziata la specificità del ruolo rivestito dai personaggi femminili nei romanzi di Germain che assumono un peso determinante nella trasmissione della memoria individuale e collettiva, studio che ci ha permesso di sottolineare la funzione attiva svolta dalle protagoniste delle opere della scrittrice. Nella fase conclusiva sono state esaminate le opere più recenti di Sylvie Germain pubblicate tra il 2008 e il 2011 in cui l’autrice sembra avvertire la necessità di controbilanciare il peso della «troppa memoria» con una giusta dose di oblio. Sono state inoltre affrontate la questione della responsabilità etica e l’idea di debito nei confronti della memoria familiare e collettiva: la scrittura stessa diventa così per Germain lo strumento attraverso il quale l’autrice assume il ruolo di passeuse de mémoire per le generazioni future.

The role of collective action in the provision of agri-environmental public goods: theoretical development through case studies in Italy

The thesis aims at analysing the role of collective action as a viable alternative to the traditional forms of intervention in agriculture in order to encourage the provision of agri-environmental public goods. Which are the main benefits of collective action, in terms of effectiveness and efficiency, compared to traditional market or public intervention policies? What are the drivers that encourage farmers to participate into collective action? To what extent it is possible to incorporate collective aspects into policies aimed at providing agri-environmental public goods? With the objective of addressing these research questions, the thesis is articulated in two levels: a theoretical analysis on the role of collective action in the provision of public goods and a specific investigation of two local initiative,s were an approach collective management of agro-environmental resources was successfully implemented. The first case study concerns a project named “Custodians of the Territory”, developed by the local agency in Tuscany “Comunità Montana Media Valle del Serchio”, which settled for an agreement with local farmers for a collective provision of environmental services related to the hydro-geological management of the district. The second case study is related to the territorial agri-environmental agreement experimented in Valdaso (Marche), where local farmers have adopted integrated pest management practices collectively with the aim of reducing the environmental impact of their farming practices. The analysis of these initiatives, carried out through participatory methods (Rapid Rural Appraisal), allowed developing a theoretical discussion on the role of innovative tools (such as co-production and co-management) in the provision of agri-environmental public goods. The case studies also provided some recommendations on the government intervention and policies needed to promote successful collective action for the provision of agri-environmental public goods.

A threshold hypothesis of institutional change: collective action in the Italian Alps during the 13th - 19th centuries.

This dissertation is about collective action issues in common property resources. Its focus is the “threshold hypothesis,” which posits the existence of a threshold in group size that drives the process of institutional change. This hypothesis is tested using a six-century dataset concerning the management of the commons by hundreds of communities in the Italian Alps. The analysis seeks to determine the group size threshold and the institutional changes that occur when groups cross this threshold. There are five main findings. First, the number of individuals in villages remained stable for six centuries, despite the population in the region tripling in the same period. Second, the longitudinal analysis of face-to-face assemblies and community size led to the empirical identification of a threshold size that triggered the transition from informal to more formal regimes to manage common property resources. Third, when groups increased in size, gradual organizational changes took place: large groups split into independent subgroups or structured interactions into multiple layers while maintaining a single formal organization. Fourth, resource heterogeneity seemed to have had no significant impact on various institutional characteristics. Fifth, social heterogeneity showed statistically significant impacts, especially on institutional complexity, consensus, and the relative importance of governance rules versus resource management rules. Overall, the empirical evidence from this research supports the “threshold hypothesis.” These findings shed light on the rationale of institutional change in common property regimes, and clarify the mechanisms of collective action in traditional societies. Further research may generalize these conclusions to other domains of collective action and to present-day applications.

Percieved Organizational Efficacy in Internationalized Companies: Application of Competing Values Approach and Collective Efficacy

This dissertation focuses on “organizational efficacy”, in particular on employees’ beliefs of organizational capacity to be efficacious. Organizational efficacy is considered from two perspectives – competing values approach and collective efficacy, and evaluated in internationalized companies. The dissertation is composed of three studies. The data were collected in thirteen Italian companies on different stages of internationalization for a total number of respondents is 358. In the first study the factorial validity of the competing values instrument (Rohrbaugh, 1981) was investigated and confirmed. Two scales were used to measure collective efficacy: a general collective efficacy scale (Bohn, 2010), and a specific collective efficacy scale, developed following suggestions of Borgogni et al. (2001), it evaluates employees’ beliefs of efficacy of organizations in the international market. The findings suggest that competing values and collective organizational efficacy instruments may provide a multi-faceted measurement of employees’ beliefs of organizational efficacy. The second study examined the relationship between organizational efficacy and collective work engagement. To measure collective work engagement the UWES-9 (Schaufeli & Bakker, 2003) was adapted at the group level; its factor structure and reliability were similar to the standard UWES-9. The findings suggest that organizational efficacy fully predicts collective work engagement. Also we investigated whether leadership moderates the relationship between organizational efficacy and collective work engagement. We operationalized leadership style with MLQ (Bass & Avolio, 1995); the results suggest that intellectual stimulation and idealized influence (transformational leadership) and contingent reward (transactional leadership) enhance the impact of organizational efficacy on collective work engagement. In the third study we investigated organizational efficacy and collective work engagement in internationalized companies. The findings show that beliefs of organizational efficacy vary across companies in different stages of internationalization, while no significant difference was found for collective work engagement. Limitations, practical implications and future studies are discussed in the conclusion.