On the quasiparticle description of c=1 CFTs

We show that the description of $c=1$ Conformal Field Theory in terms of quasiparticles satisfying fractional statistics can be obtained from the sine-Gordon model with a chemical potential $A$, in the limit where $A \gg M$. These quasiparticles are related to the excitations of the Calogero-Sutherland (CS) model. We provide a direct calculation of their 2-particle S-matrix using Korepin's method. We also reconsider the computation of the CS S-matrix in terms of particles with fractional charge

Progettazione e sviluppo di una mano robotica sotto-attuata per robot umanoide bipede

Lo scopo di questo lavoro è la progettazione e lo sviluppo di una mano robotica antropomorfa che possa essere integrata sul robot bipede SABIAN. L'esame dello stato dell'arte verte sulle mani robotiche per robot umanoidi presenti nella letteratura scientifica, con particolare attenzione ai meccanismi di trasmissione. L'obiettivo è quello di progettare una mano facilmente controllabile con un ridotto numero di attuatori che sia in grado di realizzare operazioni di presa anche in ambiente non strutturato e gestualità avanzata. Un'accurata analisi della trasmissione sotto-attuata e l'individuazione di indici globali di performance ha permesso di strutturare una procedura di ottimizzazione volta alla prevenzione dei fenomeni di instabilità della presa. Il dimensionamento del sistema di estensione passivo segue sulla base del Know-How dell'ARTS-lab, che unitamente al controllo, si prefigge lo scopo di replicare la dinamica del dito umano nella fase di chiusura prima della presa. Il lavoro si è concluso con la progettazione della mano e dell'unità di attuazione, puntando l'attenzione all'integrazione dei sensori nella struttura e la realizzazione delle dita

Thermodynamics of Fateev's models in the Presence of External Fields

We study the Thermodynamic Bethe Ansatz equations for a one-parameter quantum field theory recently introduced by V.A.Fateev. The presence of chemical potentials produces a kink condensate that modifies the excitation spectrum. For some combinations of the chemical potentials an additional gapless mode appears. Various energy scales emerge in the problem. An effective field theory, describing the low energy excitations, is also introduced.Comment: To appear in Nucl.Phys.

Exactly solvable model for isospin S=3/2 fermionic atoms on an optical lattice

We propose an exact solution of a model describing a low energy behavior of cold isospin S=3/2 fermionic atoms on a one-dimensional optical lattice. Depending on the band filling the effective field theory has a form of a deformed Gross-Neveu model with either $O(7)\times \mathbb{Z}_2$ (half filling) or $U(1)\times O(5)\times \mathbb{Z}_2$ symmetry.Comment: 4 pages, no figures, replaced with the final version to appear in PR

The SmartHand transradial prosthesis

<p>Abstract</p> <p>Background</p> <p>Prosthetic components and control interfaces for upper limb amputees have barely changed in the past 40 years. Many transradial prostheses have been developed in the past, nonetheless most of them would be inappropriate if/when a large bandwidth human-machine interface for control and perception would be available, due to either their limited (or inexistent) sensorization or limited dexterity. <it>SmartHand </it>tackles this issue as is meant to be clinically experimented in amputees employing different neuro-interfaces, in order to investigate their effectiveness. This paper presents the design and on bench evaluation of the SmartHand.</p> <p>Methods</p> <p>SmartHand design was bio-inspired in terms of its physical appearance, kinematics, sensorization, and its multilevel control system. Underactuated fingers and differential mechanisms were designed and exploited in order to fit all mechatronic components in the size and weight of a natural human hand. Its sensory system was designed with the aim of delivering significant afferent information to the user through adequate interfaces.</p> <p>Results</p> <p>SmartHand is a five fingered self-contained robotic hand, with 16 degrees of freedom, actuated by 4 motors. It integrates a bio-inspired sensory system composed of 40 proprioceptive and exteroceptive sensors and a customized embedded controller both employed for implementing automatic grasp control and for potentially delivering sensory feedback to the amputee. It is able to perform everyday grasps, count and independently point the index. The weight (530 g) and speed (closing time: 1.5 seconds) are comparable to actual commercial prostheses. It is able to lift a 10 kg suitcase; slippage tests showed that within particular friction and geometric conditions the hand is able to stably grasp up to 3.6 kg cylindrical objects.</p> <p>Conclusions</p> <p>Due to its unique embedded features and human-size, the SmartHand holds the promise to be experimentally fitted on transradial amputees and employed as a bi-directional instrument for investigating -during realistic experiments- different interfaces, control and feedback strategies in neuro-engineering studies.</p

Scaling of excitations in dimerized and frustrated spin-1/2 chains

We study the finite-size behavior of the low-lying excitations of spin-1/2 Heisenberg chains with dimerization and next-to-nearest neighbors interaction, J_2. The numerical analysis, performed using density-matrix renormalization group, confirms previous exact diagonalization results, and shows that, for different values of the dimerization parameter \delta, the elementary triplet and singlet excitations present a clear scaling behavior in a wide range of \ell=L/\xi (where L is the length of the chain and \xi is the correlation length). At J_2=J_2c, where no logarithmic corrections are present, we compare the numerical results with finite-size predictions for the sine-Gordon model obtained using Luscher's theory. For small \delta we find a very good agreement for \ell > 4 or 7 depending on the excitation considered.Comment: 4 pages, 4 eps figures, RevTeX 4 class, same version as in PR

Mass Generation in Perturbed Massless Integrable Models

We extend form-factor perturbation theory to non--integrable deformations of massless integrable models, in order to address the problem of mass generation in such systems. With respect to the standard renormalisation group analysis this approach is more suitable for studying the particle content of the perturbed theory. Analogously to the massive case, interesting information can be obtained already at first order, such as the identification of the operators which create a mass gap and those which induce the confinement of the massless particles in the perturbed theory

Exactly Solvable Ginzburg-Landau theories of Superconducting Order Parameters coupled to Elastic Modes

We consider two families of exactly solvable models describing thermal fluctuations in two-dimensional superconductors coupled to phonons living in an insulating layer, and study the stability of the superconducting state with respect to vortices. The two families are characterized by one or two superconducting planes. The results suggest that the effective critical temperature increases with the thickness of the insulating layer. Also the presence of the additional superconducting layer has the same effect.Comment: Submitted to Physical Review