Microscopic Deterministic Dynamics and Persistence Exponent

Numerically we solve the microscopic deterministic equations of motion with random initial states for the two-dimensional $\phi^4$ theory. Scaling behavior of the persistence probability at criticality is systematically investigated and the persistence exponent is estimated.Comment: to appear in Mod. Phys. Lett.

Symposium on Mario Diani’s book. An Introduction

For Symopium abstract is not require

Extreme Right and Populism: A Frame Analysis of Extreme Right Wing Discourses in Italy and Germany. IHS Political Science Series No. 121, July 2010

This paper addresses the interactions between the extreme right and populism, looking at right wing discourses in Italy and Germany, focusing on different types of extreme right organizations (political parties, violent subcultural/young right wing groups, and political movements), and adopting a social movement perspective. Through a frame analysis conducted on several types of organizational documents (newspapers, websites, online guest books and forums, and other forms of publications), covering a period from 2000-2006, for a total of 4000 frames, it explores empirically the aspect of the conceptualization of the populism by the extreme right, showing the bridging of the appeal to the people with some traditional frames of the extreme right, such as nativism and authoritarianism, and stressing how the central populist frames (the people versus the elite) are linked to the extreme right definition of the 'us' and the 'them', when developing diagnoses, prognoses and motivations to action. A political opportunity and discursive approach will be useful in explaining the different configurations of populist frames depending on country and organizational type

Geometry of dynamics and phase transitions in classical lattice phi^4 theories

We perform a microcanonical study of classical lattice phi^4 field models in 3 dimensions with O(n) symmetries. The Hamiltonian flows associated to these systems that undergo a second order phase transition in the thermodynamic limit are here investigated. The microscopic Hamiltonian dynamics neatly reveals the presence of a phase transition through the time averages of conventional thermodynamical observables. Moreover, peculiar behaviors of the largest Lyapunov exponents at the transition point are observed. A Riemannian geometrization of Hamiltonian dynamics is then used to introduce other relevant observables, that are measured as functions of both energy density and temperature. On the basis of a simple and abstract geometric model, we suggest that the apparently singular behaviour of these geometric observables might probe a major topological change of the manifolds whose geodesics are the natural motions.Comment: REVTeX, 15 PostScript figures, published versio

When topology triggers a phase transition

Two mathematical mechanisms, responsible for the generation of a thermodynamic singularity, are individuated. For a class of short-range, confining potentials, a topology change in some family of configuration space submanifolds is the only possible such mechanism. Two examples of systems in which the phase transition is not accompanied by a such topology change are discussed. The first one is a model with long-range interactions, namely the mean-field phi^4-model, the second example is a one-dimensional system with a non-confining potential energy function. For both these systems, the thermodynamic singularity is generated by a maximization over one variable (or one discrete index) of a smooth function, although the context in which the maximization occurs is very different.Comment: Talk given at the Next-SigmaPhi conference in Kolymbari, Crete, Greece, August 13-18, 200

Phase Ordering Dynamics of ϕ4\phi^4 Theory with Hamiltonian Equations of Motion

Phase ordering dynamics of the (2+1)- and (3+1)-dimensional $\phi^4$ theory with Hamiltonian equations of motion is investigated numerically. Dynamic scaling is confirmed. The dynamic exponent $z$ is different from that of the Ising model with dynamics of model A, while the exponent $\lambda$ is the same.Comment: to appear in Int. J. Mod. Phys.

An Agent-Based Model of Schumpeterian Competition

The paper presents an Agent-Based extension of Nelson-Winter model of schumpeterian competition. The original version did not provide any insight about the direction of firms innovative activities and of technological change as a whole. As a result, it lacked an explicit structure governing firms interaction and the shape of externalities. We address these criticisms by taking explicitly into account the structure of technology in use in the industry, that we shape as a directed network of nodes and links: nodes represent technological skills to be learnt by firms looking for new combinations and links represent their reciprocal interdependencies. The network is created in order to reflect the defining properties of Technological Paradigms and Technological Trajectories, as they emerge by evolutive-neoschumpeterian literature. Firms ability to learn technological skills through imitation of competitors generates spillover effects related to the process of diffusion of innovation. The basic model presented here focuses on a particular aspect of schumpeterian competition: the relationship between industry initial concentration and its overall innovative performance and, vice-versa, between innovation process and the evolution of industry structure over time. In this same perspective we also analyze how firms interactions and the structure of technology concur in determining the success or failure of an innovative strategy. Finally we argue that the model presented here might constitute a flexible framework worthy of further applications in the study of innovation process and technological progress

Topological origin of the phase transition in a mean-field model

We argue that the phase transition in the mean-field XY model is related to a particular change in the topology of its configuration space. The nature of this topological transition can be discussed on the basis of elementary Morse theory using the potential energy per particle V as a Morse function. The value of V where such a topological transition occurs equals the thermodynamic value of V at the phase transition and the number of (Morse) critical points grows very fast with the number of particles N. Furthermore, as in statistical mechanics, also in topology the way the thermodynamic limit is taken is crucial.Comment: REVTeX, 5 pages, with 1 eps figure included. Some changes in the text. To appear in Physical Review Letter

Louis XVI’s Chapel during the French Revolution 1789-1792

Abstract — The close association of Christianity with the late Bourbon monarchy’s style of governance has often been interpreted as a burdensome legacy, which impacted greatly on the period preceding the French Revolution. In recent years, historians have referred to the ideological, juridical and intellectual assaults on the religious foundations of the French crown, throughout the eighteenth century, either as a process of ‘ desacralization ’ or as the religious origins of the French Revolution. This article, though inspired by this school of thought, takes a different approach by examining the less well-known ceremonial and ritual components of this form of kingship, with particular reference to the king’s chapel. Louis XVI’s ecclesiastical household was both the centre of royal patronage for the Gallican Church and the chief regulatory authority of the monarch’s personal religious devotion. Its actions, transformation and fate during the Revolution are instructive in two ways. First, its survival during the first three years of the revolutionary troubles highlights its fundamental and constraining influence over the French monarchy. Secondly, the gradual, though determined, effort to undermine the pact between throne and altar that it represented exemplifi es a lesser known aspect of the national deputies ’ anticlerical agenda