1435 research outputs found
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The Magnetic Monopole Seventy-Five Years Later
No full textNon-Abelian monopoles are present in the fully quantum mechanical low-energy
effective action of many solvable supersymmetric theories. They behave
perfectly as pointlike particles carrying non-Abelian dual magnetic charges.
They play a crucial role in confinement and in dynamical symmetry breaking in
these theories. There is a natural identification of these excitations within
the semiclassical approach, which involves the flavor symmetry in an essential
manner. We review, in an introductory fashion, the recent development which has
led to a better understanding of the nature of non-Abelian monopoles and of
their role in confinement and dynamical symmetry breaking in strongly
interacting theories
SU(N) gauge theories in the presence of a topological term
No full textWe review recent results on the theta dependence of the ground-state energy
and spectrum of four-dimensional SU(N) gauge theories, where theta is the
coefficient of the CP-violating topological term F-Fdual in the Lagrangian. In
particular, we discuss the results obtained by Monte Carlo simulations of the
lattice formulation of QCD, which allow the investigation of theta dependence
around theta=0 by determining the moments of the topological charge
distribution, and their correlations with other observables. The results for
N=3 and larger values of N support the scenario obtained by general large-N
scaling arguments
Adiabatic divergence of the chaotic layer width and acceleration of chaotic and noise-induced transport
No full textSUMMARY We show that, in spatially periodic Hamiltonian systems driven by a time-periodic coordinate-independent (AC) force, the upper energy of the chaotic layer grows unlimitedly as the frequency of the force goes to zero. This remarkable effect is absent in any other physically significant systems. It gives rise to the divergence of the rate of the spatial chaotic transport. We also generalize this phenomenon for the presence of a weak noise and weak dissipation. We demonstrate for the latter case that the adiabatic AC force may greatly accelerate the spatial diffusion and the reset rate at a given threshold
Characterization and measurement of stone engravings
No full textEngraving by waterjet and laser processing is an emerging stone process for product identification and traceability (characters or codes) and for decoration (inlay). The main characterization and measurement issues for the optimization of the engraving process and for product inspection are discussed. Stylus measurement is not suitable for accessibility and for the very steep surfaces, so an optical profilometer and a specific setup, has been developed. A special measurement method and algorithm is proposed to define the main geometric features of engravings at microscopic level. Based on our analysis the conventional engraving width and several quality measures have been defined
Diamond wire cutting: failure modes, risks for safety and workers’ protection
No full textDespite the fast development and diffusion of diamond wire cutting, the intrinsic risk of death caused by the ejection of diamond beads in case of wire breakage is still an open problem. This project, sponsored by Italian Carrara manufacturers, aims to evaluate and improve the safety of diamond wire saw machines. This paper describes the phenomena occurring immediately after wire breakage during squaring operations of marble blocks. The results of a systematic series of full-scale experiments with provoked breakage and of laboratory wire testing are provided. Over 30 experiments have been documented by high-speed imaging and analyzed in two conditions: without protections, to examine the behaviour of a free diamond wire (which has been also simulated by a numerical model) and with various protection equipments, to assess their effectiveness in eliminating all or at least drastically reducing risks for workers
An Intermediate Language for Stochastic Simulation of Biological Systems
No full textWe introduce Stochastic String MultiSet Rewriting (sSMSR), and propose this formalism as an intermediate language for the simulation of biomolecular systems. Higher level formalisms for biological systems description can be translated into sSMSR, and the features of sSMSR allow the development of efficient simulators. In this paper, we show the encoding into sSMSR of two formalisms for the description of biological systems, namely Stochastic CLS and the Stochastic π-calculus. We prove soundness and completeness of both the encodings
A test of first order scaling in Nf =2 QCD: a progress report
No full textSUMMARY We present the status of our analysis on the order of the finite temperature
transition in QCD with two flavors of degenerate fermions. Our new simulations
on large lattices support the hypothesis of the first order nature of the
transition, showing a preliminary two state signal. We will discuss the
implications and the next steps in our analysis
Using a hierarchical properties ranking with AHP for the ranking of electoral systems
No full textElectoral systems are complex entities composed of a set of phases that form a process to which performance parameters can be associated.
One of the key points of every electoral system is represented by the electoral formula that can be characterized by a wide spectrum of properties that, according to Arrow's Impossibility Theorem and other theoretical results, cannot be all satisfied at the same time. Starting from these basic results the aim of this paper is to examine such properties within a hierarchical framework, based on {Analytic Hierarchy Process} proposed by T. L. Saaty, performing pairwise comparisons at various levels of a hierarchy so to get a global ranking of such properties. Since any real electoral system is known to satisfy some of such properties but not others it should be possible, in this way, to get a ranking of the electoral systems according also to the political goals both of the voters and the candidates. In this way it should be possible to estimate the relative importance of each property with respect to the final ranking of every electoral formula
A large N phase transition in the continuum two dimensional SU(N) X SU(N) principal chiral model
No full textIt is established by numerical means that the continuum large N principal
chiral model in two dimensions has a phase transition in a smoothed two point
function at a critical distance of the order of the correlation length
Toward a Formal Semantics for Autonomic Components
No full textAutonomic management can improve the QoS provided by parallel/distributed applications. Within the CoreGRID Component Model, the autonomic management is tailored to the automatic - monitoring-driven - alteration of the component assembly and, therefore, is defined as the effect of (distributed) management code. This work yields a semantics based on hypergraph rewriting suitable to model the dynamic evolution and non-functional aspects of Service Oriented Architectures and component-based autonomic applications. In this regard, our main goal is to provide a formal description of adaptation operations that are typically only informally specified. We contend that our approach makes easier to raise the level of abstraction of management code in autonomic and adaptive applications