The effect of massed compared with massed followed by evenly spaced practice on the learning of a motor skill

Thesis (Ed.M.)--Boston Universit

The Classical Spectral Density Method at Work: The Heisenberg Ferromagnet

In this article we review a less known unperturbative and powerful many-body method in the framework of classical statistical mechanics and then we show how it works by means of explicit calculations for a nontrivial classical model. The formalism of two-time Green functions in classical statistical mechanics is presented in a form parallel to the well known quantum counterpart, focusing on the spectral properties which involve the important concept of spectral density. Furthermore, the general ingredients of the classical spectral density method (CSDM) are presented with insights for systematic nonperturbative approximations to study conveniently the macroscopic properties of a wide variety of classical many-body systems also involving phase transitions. The method is implemented by means of key ideas for exploring the spectrum of elementary excitations and the damping effects within a unified formalism. Then, the effectiveness of the CSDM is tested with explicit calculations for the classical $d$-dimensional spin-$S$ Heisenberg ferromagnetic model with long-range exchange interactions decaying as $r^{-p}$ ($p>d$) with distance $r$ between spins and in the presence of an external magnetic field. The analysis of the thermodynamic and critical properties, performed by means of the CSDM to the lowest order of approximation, shows clearly that nontrivial results can be obtained in a relatively simple manner already to this lower stage. The basic spectral density equations for the next higher order level are also presented and the damping of elementary spin excitations in the low temperature regime is studied. The results appear in reasonable agreement with available exact ones and Monte Carlo simulations and this supports the CSDM as a promising method of investigation in classical many-body theory.Comment: Latex, 58 pages, 12 figure

Spectral density method in quantum nonextensive thermostatistics and magnetic systems with long-range interactions

Motived by the necessity of explicit and reliable calculations, as a valid contribution to clarify the effectiveness and, possibly, the limits of the Tsallis thermostatistics, we formulate the Two-Time Green Functions Method in nonextensive quantum statistical mechanics within the optimal Lagrange multiplier framework, focusing on the basic ingredients of the related Spectral Density Method. Besides, to show how the SDM works we have performed, to the lowest order of approximation, explicit calculations of the low-temperature properties for a quantum $d$-dimensional spin-1/2 Heisenberg ferromagnet with long-range interactions decaying as $1/r^{p}$ ($r$ is the distance between spins in the lattice)Comment: Contribution to Next-SigmaPhi conference in Kolymbari, Crete, Greece, August 13-18, 2005, 9 page

Two-time Green's functions and spectral density method in nonextensive quantum statistical mechanics

We extend the formalism of the thermodynamic two-time Green's functions to nonextensive quantum statistical mechanics. Working in the optimal Lagrangian multipliers representation, the $q$-spectral properties and the methods for a direct calculation of the two-time $q$% -Green's functions and the related $q$-spectral density ($q$ measures the nonextensivity degree) for two generic operators are presented in strict analogy with the extensive ($q=1$) counterpart. Some emphasis is devoted to the nonextensive version of the less known spectral density method whose effectiveness in exploring equilibrium and transport properties of a wide variety of systems has been well established in conventional classical and quantum many-body physics. To check how both the equations of motion and the spectral density methods work to study the $q$-induced nonextensivity effects in nontrivial many-body problems, we focus on the equilibrium properties of a second-quantized model for a high-density Bose gas with strong attraction between particles for which exact results exist in extensive conditions. Remarkably, the contributions to several thermodynamic quantities of the $q$-induced nonextensivity close to the extensive regime are explicitly calculated in the low-temperature regime by overcoming the calculation of the $q$ grand-partition function.Comment: 48 pages, no figure

The Theory Behind TheoryMine

Abstract. We describe the technology behind the TheoryMine novelty gift company, which sells the rights to name novel mathematical theorems. A tower of four computer systems is used to generate recursive theories, then to speculate conjectures in those theories and then to prove these conjectures. All stages of the process are entirely automatic. The process guarantees large numbers of sound, novel theorems of some intrinsic merit.

On the hosts of neutron star mergers in the nearby Universe

Recently, the characterisation of binary systems of neutron stars has become central in various fields such as gravitational waves, gamma-ray bursts (GRBs), and the chemical evolution of galaxies. In this work, we explore possible observational proxies that can be used to infer some characteristics of the delay time distribution (DTD) of neutron star mergers (NSMs). We construct a sample of model galaxies that fulfils the observed galaxy stellar mass function, star formation rate versus mass relation, and the cosmic star formation rate density. The star formation history of galaxies is described with a log-normal function characterised by two parameters: the position of the maximum and the width of the distribution. We assume a theoretical DTD that mainly depends on the lower limit and the slope of the distribution of the separations of the binary neutron stars systems at birth. We find that the current rate of NSMs ($\mathcal{R}=320^{+490}_{-240}$ Gpc$^{-3}$yr$^{-1}$) requires that $\sim0.3$ per cent of neutron star progenitors lives in binary systems with the right characteristics to lead to a NSM within a Hubble time. We explore the expected relations between the rate of NSMs and the properties of the host galaxy. We find that the most effective proxy for the shape of the DTD of NSMs is the current star formation activity of the typical host. At present, the fraction of short-GRBs observed in star-forming galaxies favours DTDs with at least $\sim40\%$ of mergers within $100$ Myr. This conclusion will be put on a stronger basis with larger samples of short-GRBs with host association (e.g. $600$ events at $z \leq 1$)Comment: 20 pages, 18 Figures, To appear on MNRA

Thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet with long-range interactions via the spectral density method

The thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet, with long-range interactions decaying as $r^{-p}$ and in the presence of an external magnetic field, is investigated by means of the spectral density method in the framework of classical statistical mechanics. We find that long-range order exists at finite temperature for $d<p<2d$ with $d\leq 2$ and for $p>d$ with $d>2$, consistently with known theorems. Besides, the related critical temperature is determined and a study of the critical properties is performed.Comment: 27 pages, 2 figures, Submitted to Physica

Liability and Emerging Digital Technologies: An EU Perspective

Il contributo affronta il tema della responsabilità per danni causati nel corso dell'uso di una nuova technologia digitale quali l'IA, o l'IoTs

DO ENVIRONMENTAL VARIABLES AFFECT THE PERFORMANCE AND TECHNICAL EFFICIENCY OF THE EUROPEAN BANKING SYSTEMS? A PARAMETRIC ANALYSIS USING THE STOCHASTIC FRONTIER APPROACH

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A plug and play transparent communication layer for cloud robotics architectures

The cloud robotics paradigm aims at enhancing the abilities of robots by using cloud services, but it still poses several challenges in the research community. Most of the current literature focuses on how to enrich specific robotic capabilities, overlooking how to effectively establish communication between the two fields. Our work proposes a &ldquo;plug-and-play&rdquo; solution to bridge the communication gap between cloud and robotic applications. The proposed solution is designed based on the mature WebSocket technology and it can be extended to any ROS-based robotic platform. The main contributions of this work are the definition of a reliable autoconnection/autoconfiguration mechanism as well as to outline a scalable communication layer that allows the effective control of multiple robots from multiple users. The &ldquo;plug-and-play&rdquo; solution was evaluated in both simulated and real scenarios. In the first case, the presence of users and robots was simulated with Robot Operating System (ROS) nodes running on five machines. In the real scenario, three non-expert users teleoperated, simultaneously, three remote robots by using the proposed communication layer with different networking protocols. Results confirmed the reliability at different levels: at startup (success_rate = 100%); during high-rate communications (message_lost = 0%); in performing open-loop spiral trajectories with enhancement, with respect to similar works; and in the quality of simultaneous teleoperations