L. Consoli

Onset of sliding friction in incommensurate systems

We study the dynamics of an incommensurate chain sliding on a periodic lattice, modeled by the Frenkel-Kontorova Hamiltonian with initial kinetic energy, without damping and driving terms. We show that the onset of friction is due to a novel type of dissipative parametric resonances, involving several resonant phonons which are driven by the (dissipationless) coupling of the center of mass motion to the phonons with the wave vector related to the modulating potential. We establish quantitative estimates for their existence in finite systems and point out the analogy with the induction phenomenon in Fermi-Ulam-Pasta lattices.

Refining the ethics of computer-made decisions: a classification of moral mediation by ubiquitous machines

Abstract In the past decades, computers have become more and more involved in society by the rise of ubiquitous systems, increasing the number of interactions between humans and IT systems. At the same time, the technology itself is getting more complex, enabling devices to act in a way that previously only humans could, based on developments in the fields of both robotics and artificial intelligence. This results in a situation in which many autonomous, intelligent and context-aware systems are involved in decisions that affect their environment. These relations between people, machines, and decisions can take many different forms, but thus far, a systematic account of machine-assisted moral decisions is lacking. This paper investigates the concept of machine-assisted moral decisions from the perspective of technological mediation. It is argued that modern machines do not only have morality in the sense of mediating the actions of humans, but that, by making their own decisions within their relations with humans, mediate morality itself. A classification is proposed to differentiate between four different types of moral relations. The moral aspects within the decisions these systems make are combined into three dimensions that describe the distinct characteristics of different types of moral mediation by machines. Based on this classification, specific guidelines for moral behavior can be provided for these systems.

Denying darwin: Views on science in the rejection of evolution by dutch protestants

Evolution has met with considerable religious opposition for 150 years and is still controversial among various religious groups. This article tries to understand the evolution controversy by reframing it as a phenomenon of public understanding of science. Three paradigms were used as hypotheses for the rejection of evolution by Dutch Protestant Christians: knowledge deficit, attitude deficit and trust deficit. Ten Dutch Protestants rejecting evolution were interviewed about their views concerning evolution and science. It was found that the main reason for rejecting evolution was an a priori decision to trust the Bible more than science. Any views on science and evolution were based on this decision, so all three hypotheses, which suggest an a posteriori decision, were found to be not sufficient to explain the rejection of evolution, even though both a knowledge deficit and a trust deficit were found for some participants. However, all respondents felt that their a priori decision was supported by scientific facts. All respondents stated that evolution does not meet the criteria for good science and is therefore as unscientific as the belief in creation. Excluding evolution from science allows the respondents to retain their positive attitudes towards science.

Vulnerabilities and responsibilities: dealing with monsters in computer security

Purpose – The purpose of this paper is to analyze information security assessment in terms of cultural categories and virtue ethics, in order to explain the cultural origin of certain types of security vulnerabilities, as well as to enable a proactive attitude towards preventing such vulnerabilities. Design/methodology/approach – Vulnerabilities in information security are compared to the concept of “monster” introduced by Martijntje Smits in philosophy of technology. The applicability of different strategies for dealing with monsters to information security is discussed, and the strategies are linked to attitudes in virtue ethics. Findings – It is concluded that the present approach can form the basis for dealing proactively with unknown future vulnerabilities in information security. Research limitations/implications – The research presented here does not define a stepwise approach for implementation of the recommended strategy in practice. This is future work. Practical implications – The results of this paper enable computer experts to rethink their attitude towards security threats, thereby reshaping their practices. Originality/value – This paper provides an alternative anthropological framework for descriptive and normative analysis of information security problems, which does not rely on the objectivity of risk.

Can aperiodicity cause superlubricity

Abstract The ground state of incommensurate structures is determined by the modulation due to the substrate potential. This causes an interplay between the motion of the center of mass and frequencies related to the modulation wavevector q. We build for the one-dimensional Frenkel-Kontorova model an analytical framework which enables us to interpret the initial behavior of the system for a broad range of initial velocities in terms of these relevant phonon modes, and to investigate the occurrence of superlubricity.

Breakdown of a conservation law in incommensurate systems

We show that invariance properties of the Lagrangian of an incommensurate system, as described by the Frenkel-Kontorova model, imply the existence of a generalized angular momentum that is an integral of motion if the system remains floating. The behavior of this quantity can therefore monitor the character of the system as floating (when it is conserved) or locked (when it is not). We find that, during the dynamics, the nonlinear couplings of our model cause parametric phonon excitations that lead to the appearance of Umklapp terms and to a sudden deviation of the generalized momentum from a constant value, signaling a dynamical transition from a floating to a pinned state. We point out that this transition is related but does not coincide with the onset of sliding friction, which can take place when the system is still floating.

Dynamical transitions in incommensurate systems

In the dynamics of the undamped Frenkel-Kontorova model with kinetic terms, we find a transition between two regimes, a floating incommensurate and a pinned incommensurate phase. This behavior is compared to the static version of the model. While in the static case the two regimes are separated by a single transition (the Aubry transition), in the dynamical case the transition is characterized by a critical region, in which different phenomena take place at different times. In this paper, the generalized angular momentum we have previously introduced, and the dynamical modulation function are used to begin a characterization of this critical region. We further elucidate the relation between these two quantities, and present preliminary results about the order of the dynamical transition.