Results for "Stefano Nichele"

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Deep Reservoir Computing Using Cellular AutomataMar 08 2017Recurrent Neural Networks (RNNs) have been a prominent concept within artificial intelligence. They are inspired by Biological Neural Networks (BNNs) and provide an intuitive and abstract representation of how BNNs work. Derived from the more generic ... More
Towards a framework for the evolution of artificial general intelligenceMar 25 2019Mar 27 2019In this work, a novel framework for the emergence of general intelligence is proposed, where agents evolve through environmental rewards and learn throughout their lifetime without supervision, i.e., self-supervised learning through embodiment. The chosen ... More
Towards a framework for the evolution of artificial general intelligenceMar 25 2019In this work, a novel framework for the emergence of general intelligence is proposed, where agents evolve through environmental rewards and learn throughout their lifetime without supervision, i.e., self-supervised learning through embodiment. The chosen ... More
Reservoir Computing Using Non-Uniform Binary Cellular AutomataFeb 13 2017The Reservoir Computing (RC) paradigm utilizes a dynamical system, i.e., a reservoir, and a linear classifier, i.e., a read-out layer, to process data from sequential classification tasks. In this paper the usage of Cellular Automata (CA) as a reservoir ... More
Autonomous Configuration of Network Parameters in Operating Systems using Evolutionary AlgorithmsAug 31 2018By default, the Linux network stack is not configured for highspeed large file transfer. The reason behind this is to save memory resources. It is possible to tune the Linux network stack by increasing the network buffers size for high-speed networks ... More
Achieving Connectivity Between Wide Areas Through Self-Organising Robot Swarm Using Embodied EvolutionJul 12 2018Abruptions to the communication infrastructure happens occasionally, where manual dedicated personnel will go out to fix the interruptions, restoring communication abilities. However, sometimes this can be dangerous to the personnel carrying out the task, ... More
Characterization of spin-orbit interactions of GaAs heavy holes using a quantum point contactMay 12 2014Jul 31 2014We present transport experiments performed in high quality quantum point contacts embedded in a GaAs two-dimensional hole gas. The strong spin-orbit interaction results in peculiar transport phenomena, including the previously observed anisotropic Zeeman ... More
Evolved Art with Transparent, Overlapping, and Geometric ShapesApr 12 2019In this work, an evolutionary art project is presented where images are approximated by transparent, overlapping and geometric shapes of different types, e.g., polygons, circles, lines. Genotypes representing features and order of the geometric shapes ... More
On a quadratic functional for scalar conservation lawsNov 12 2013We prove a quadratic interaction estimate for approximate solutions to scalar conservation laws obtained by the wavefront tracking approximation or the Glimm scheme. This quadratic estimate has been used in the literature to prove the convergence rate ... More
Hydrodynamic Limit for an Anharmonic Chain under Boundary TensionFeb 06 2018Jun 11 2018We study the hydrodynamic limit for the isothermal dynamics of an anharmonic chain under hyperbolic space-time scaling under varying tension. The temperature is kept constant by a contact with a heat bath, realised via a stochastic momentum-preserving ... More
Hydrodynamic Limit for an Anharmonic Chain under Boundary TensionFeb 06 2018We study the hydrodynamic limit for a one dimensional isothermal anharmonic finite chain in Lagrangian coordinates with hyperbolic space-time scaling. The temperature is kept constant by putting the chain in contact with a heat bath, realised via a stochastic ... More
Quadratic interaction functional for general systems of conservation lawsDec 19 2014For the Glimm scheme approximation $u_\epsilon$ to the solution of the system of conservation laws in one space dimension \begin{equation*} u_t + f(u)_x = 0, \qquad u(0,x) = u_0(x) \in \mathbb R^n, \end{equation*} with initial data $u_0$ with small total ... More
Quadratic interaction functional for systems of conservation laws: a case studyNov 12 2013We prove a quadratic interaction estimate for wavefront approximate solutions to the triangular system of conservation laws \[ \begin{cases} u_t + \tilde f(u,v)_x = 0, \cr v_t - v_x = 0. \end{cases} \] This quadratic estimate has been used in the literature ... More
A note on the existence of $L^2$ valued solutions for a hyperbolic system with boundary conditionsNov 13 2018Feb 08 2019We prove existence of $L^2$-weak solutions of a quasilinear wave equation with boundary conditions.This is done using a vanishing viscosity approximation with mixed Dirichlet-Neumann boundary conditions. In this setting we obtain a uniform a priori estimate ... More
Quantum Teleportation with Continuous Variables: a surveyApr 05 2006Oct 12 2006Very recently we have witnessed a new development of quantum information, the so-called continuous variable (CV) quantum information theory. Such a further development has been mainly due to the experimental and theoretical advantages offered by CV systems, ... More
Electron localization in pure and defective ceria by a unified LDA+U approachDec 23 2003The electronic and structural properties of pure and defective cerium oxide are investigated using a unified LDA+U approach which allows to treat the different valence states of Ce occurring for different stoichiometries on a same ground, without any ... More
Organised crime infiltration in the legitimate private economy - An empirical network analysis approachMar 20 2014It is estimated that Italian Mafias registered 135 billion euros in profits only in 2010. Part of this huge amount of money, coming mostly from the drugs, prostitution and arms illicit markets, is often used to invest into legitimate private economies. ... More
Divisorial models of normal varietiesNov 07 2012May 05 2015We prove that the canonical ring of a canonical variety in the sense of de Fernex and Hacon is finitely generated. We prove that canonical varieties are klt if and only if R(-K_X) is finitely generated. We introduce a notion of nefness for non-Q-Gorenstein ... More
Gauge boson couplings at LEPOct 14 2004A review is given of the measurements of triple and quartic couplings among the electroweak gauge bosons performed at LEP by the four experiments ALEPH, DELPHI, L3 and OPAL. Emphasis is placed on recently published results and on combinations of results ... More
A Quantum Teleportation GameJul 29 2004Nov 17 2004We investigate a game where a sender (Alice) teleports coherent states to two receivers (Bob and Charlie) through a tripartite Gaussian state. The aim of the receivers is to optimize their teleportation fidelities by means of local operations and classical ... More
Quantum Reading of a Classical Digital MemoryMar 17 2011We consider a basic model of digital memory where each cell is composed of a reflecting medium with two possible reflectivities. By fixing the mean number of photons irradiated over each memory cell, we show that a non-classical source of light can retrieve ... More
Chiral behaviour of the pion decay constant in $N_f=2$ QCDNov 13 2013Nov 25 2013As increased statistics and new ensembles with light pions have become available within the CLS effort, we complete previous work by inspecting the chiral behaviour of the pion decay constant. We discuss the validity of Chiral Perturbation Theory ($\chi$PT) ... More
GRB Afterglow Polarimetry: Past, Present and FutureJun 30 2009Gamma-ray bursts and their afterglows are thought to be produced by an ultrarelativistic jet. One of the most important open questions is the outflow composition: the energy may be carried out from the central source either as kinetic energy (of baryons ... More
Talbot self-imaging in $\mathcal{PT}$-symmetric complex crystalsSep 28 2014The Talbot effect, i.e. the self-imaging property of a periodic wave in near-field diffraction, is a remarkable interference phenomenon in paraxial systems with continuous translational invariance. In crystals, i.e. systems with discrete translational ... More
Many-body coherent destruction of tunneling in photonic latticesNov 15 2011An optical realization of the phenomenon of many-body coherent destruction of tunneling, recently predicted for interacting many-boson systems by Gong, Molina and Haenggi [Phys. Rev. Lett. 103, 133002 (2009)], is proposed for light transport in engineered ... More
Classical Simulation of Relativistic Quantum Mechanics in Periodic Optical StructuresNov 15 2011Spatial and/or temporal propagation of light waves in periodic optical structures offers a rather unique possibility to realize in a purely classical setting the optical analogues of a wide variety of quantum phenomena rooted in relativistic wave equations. ... More
Optical realization of the two-site Bose-Hubbard model in waveguide latticesJan 25 2011A classical realization of the two-site Bose-Hubbard Hamiltonian, based on light transport in engineered optical waveguide lattices, is theoretically proposed. The optical lattice enables a direct visualization of the Bose-Hubbard dynamics in Fock space. ... More
Low-frequency anomalies in dynamic localizationMay 11 2014Quantum mechanical spreading of a particle hopping on tight binding lattices can be suppressed by the application of an external ac force, leading to periodic wave packet reconstruction. Such a phenomenon, referred to as dynamic localization (DL), occurs ... More
Bound states in the continuum in PT-symmetric optical latticesFeb 16 2014Bound states in the continuum (BIC), i.e. normalizable modes with an energy embedded in the continuous spectrum of scattered states, are shown to exist in certain optical waveguide lattices with $\mathcal{PT}$-symmetric defects. Two distinct types of ... More
Quantum simulation of decoherence in optical waveguide latticesOct 27 2013We suggest that propagation of nonclassical light in lattices of optical waveguides can provide a laboratory tool to simulate quantum decoherence phenomena with high non-Markovian features. As examples, we study decoherence of optical Schr\"{o}dinger ... More
Invisibility in non-Hermitian tight-binding latticesAug 31 2010Reflectionless defects in Hermitian tight-binding lattices, synthesized by the intertwining operator technique of supersymmetric quantum mechanics, are generally not invisible and time-of-flight measurements could reveal the existence of the defects. ... More
Spatio-temporal wave propagation in photonic crystals: a Wannier-function analysisSep 02 2004A general analysis of undistorted propagation of localized wavepackets in photonic crystals based on a Wannier-function expansion technique is presented. Different kinds of propagating and stationary spatio-temporal localized waves are found from an asymptotic ... More
WKB metastable quantum states of a de Sitter--Reissner-Nordstroem dust shellOct 01 2003We study the dynamics of a spherically symmetric dust shell separating two spacetime domains, the 'interior' one being a part of the de Sitter spacetime and the exterior one having the 'extremal' Reissner-Nordstroem geometry. Extending the ideas of previous ... More
Selective cloning of Gaussian states by linear opticsApr 23 2007We investigate the performances of a selective cloning machine based on linear optical elements and Gaussian measurements, which allows to clone at will one of the two incoming input states. This machine is a complete generalization of a 1 to 2 cloning ... More
A comment on anti-brane singularities in warped throatsFeb 16 2012We compute the imaginary self-dual (ISD) and imaginary anti-self-dual (IASD) fluxes for the Klebanov-Strassler background perturbed by a stack of p anti-D3 branes. We show that, at linear order in p, they both have a singularity in the near-brane region. ... More
Metastable Vacua and the Backreacted Stenzel GeometryOct 11 2011We construct an M-theory background dual to the metastable state recently discussed by Klebanov and Pufu, which corresponds to placing a stack of anti-M2 branes at the tip of a warped Stenzel space. With this purpose we analytically solve for the linearized ... More
Standard Model Higgs boson production and hard photon radiation in $e^+e^-\to μ^+μ^- b\bar bγ$ events at LEP II and Next Linear ColliderDec 22 1995Mar 28 1996We study at LEP II and Next Linear Collider energies Higgs production via the bremsstrahlung channel $e^+e^-\ar ZH$, with $Z\ar \mu^+\mu^-$ and $H\ar b\bar b$, and the corresponding irreducible background, in presence of hard photon radiation, both from ... More
Heavy Higgs production and decay via $e^+e^-\to Z^0 H^0 \to b\bar bZ^0Z^0$ and irreducible backgrounds at Next Linear CollidersJan 14 1995The complete matrix element for $e^+e^-\ar b\bar bZ^0Z^0$ has been computed at tree--level and applied to $Z^0H^0$--production followed by $Z^0\ar b\bar b$ and $H^0\ar Z^0Z^0$, including all the irreducible background, at Next Linear Colliders. We find ... More
Given Talk at Moriond 2006: Fermion Mass in E6 GUT with Discrete Family Permutation Symmetry S3May 15 2006A discrete symmetry S3 easily explains all neutrino data. However it is not obvious the embedding of S3 in GUT where all fermions live in the same representation. We show that embedding S3 in E6 it is possible to make distinction between neutrinos and ... More
Transmutation of N=2 fractional D3 branes into twisted sector fluxesApr 15 2009Jun 23 2009We study the prototype of fractional D3 branes at non-isolated singularities in gauge/gravity duality at the nonperturbative level. We embed the quantum moduli space of N=2 SU(M) pure SYM, the gauge theory on fractional D3 branes at the A_1 singularity, ... More
Anomaly-Induced Magnetic Screening in 2+1 dimensional QED at Finite DensityMar 19 1993May 20 1993We show that in 2+1 dimensional Quantum Electrodynamics an external magnetic field applied to a finite density of massless fermions is screened, due to a $2+1$-dimensional realization of the underlying $2$-dimensional axial anomaly of the space components ... More
Gravity-analogy in one-dimensional ideal Fermi fluids and Burgers' equationOct 14 2010An hydrodynamic description of a one-dimensional flow of an ideal Fermi fluid is constructed from a semiclassical approximation. For an initially fully degenerate fluid, Euler and continuity hydrodynamic equations are dual to two uncoupled inviscid Burgers' ... More
Short-term Predictable Power of a Wind Farm via Distributed Control of Wind Generators with Integrated StorageFeb 12 2016In this paper we introduce a Leader-follower consensus protocol and study its stability properties with and without communication delays. On the practical side, we explore its application on coordinating a group of wind Double-Fed Induction Generators ... More
Static BPS black holes in U(1) gauged supergravityMay 19 2014Sep 08 2014We consider the flow equations for $1/4$-BPS asymptotically AdS$_4$ static black holes in Fayet-Iliopoulos gauged supergravity, using very special geometry identities to obtain a simplified form in the most general case. Under mild assumptions on the ... More
Shearing a glass and the role of pin-delay in models of interface depinningOct 21 2013Aug 04 2014When a disordered solid is sheared, yielding is followed by the onset of intermittent response that is characterized by slip in local regions usually labeled shear-transformation zones (STZ). Such intermittent response resembles the behavior of earthquakes ... More
A counterexample for a suptheorem in locally convex spacesOct 12 2009Oct 24 2009In this brief note, we provide an example of non complete locally convex space $E$ with a $\sigma(E, E^*)$ closed bounded subset $C\subset E$, which is not $\sigma(E, E^*)$-compact, even if every $\varphi\in E^*$ attains its sup over $C$.
A successive sub-grouping method for multiple sequence alignments analysisMay 30 2007Jun 07 2007A novel approach to protein multiple sequence alignment is discussed: substantially this method counterparts with substitution matrix based methods (like Blosum or PAM based methods), and implies a more deterministic approach to chemical/physical sub-grouping ... More
Gamma Ray Astronomy and the Origin of Galactic Cosmic RaysNov 05 2008Diffusive shock acceleration operating at expanding supernova remnant shells is by far the most popular model for the origin of galactic cosmic rays. Despite the general consensus received by this model, an unambiguous and conclusive proof of the supernova ... More
Shock acceleration and gamma radiation in the intracluster mediumJan 08 2004Particle acceleration is expected to take place at shocks that form during the process of large scale structure formation. Electrons accelerated at such shocks can upscatter a small fraction of the photons in the cosmic microwave background up to the ... More
Spectroscopy of D MesonsDec 29 2005Feb 12 2006The scenario of heavy quark meson spectroscopy underwent recently a major revolution, after the observation of BABAR and CLEO, confirmed by BELLE, of $\DsJ$ L=1 excited states, and by further evidences by SELEX. These experimental results have cast doubts ... More
Particle Dark Matter CandidatesNov 19 2007Nov 27 2007I give a short overview on some of the favorite particle Cold Dark Matter candidates today, focusing on those having detectable interactions: the axion, the KK-photon in Universal Extra Dimensions, the heavy photon in Little Higgs and the neutralino in ... More
Solar cycle full-shape predictions: a global error evaluation for cycle 24Jun 06 2016There are many proposed prediction methods for solar cycles behavior. In a previous paper we updated the full-shape curve prediction of the current solar cycle 24 using a non-linear dynamics method and we compared the results with the predictions collected ... More
Guitar Solos as NetworksMar 16 2016This paper presents an approach to model melodies (and music pieces in general) as networks. Notes of a melody can be seen as nodes of a network that are connected whenever these are played in sequence. This creates a directed graph. By using complex ... More
Synthetic gauge fields for light beams in optical resonatorsApr 30 2015A method to realize artificial magnetic fields for light waves trapped in passive optical cavities with anamorphic optical elements is theoretically proposed. In particular, when a homogeneous magnetic field is realized, a highly-degenerate Landau level ... More
Light Sterile Neutrinos In CosmologyJan 07 2016We briefly discuss the main effects of the presence of a Light Sterile Neutrino (LS$\nu$) in Cosmology and how its properties can be constrained by Cosmic Microwave Background (CMB) and other cosmological measurements.
Capacities of repeater-assisted quantum communicationsJan 05 2016Jul 03 2016We establish the ultimate rates for transmitting quantum information, distilling entanglement, and distributing secret keys in repeater-assisted quantum communications, under the most fundamental decoherence models for both discrete and continuous variable ... More
Tight-binding lattices with an oscillating imaginary gauge fieldMar 30 2016We consider non-Hermitian dynamics of a quantum particle hopping on a one-dimensional tight-binding lattice made of $N$ sites with asymmetric hopping rates induced by a time-periodic oscillating imaginary gauge field. A deeply different behavior is found ... More
Light sterile neutrinos and pseudoscalar interactions in cosmologyOct 05 2016The Short BaseLine (SBL) neutrino oscillations anomalies hint at the presence of a sterile neutrino with a mass of around 1 eV. However, such neutrino is highly incompatible with the cosmological data, in particular from the Cosmic Microwave Background ... More
Do not mess with time: Probing faster than light travel and chronology protection with superluminal warp drivesJan 05 2016While General Relativity ranks undoubtedly among the best physics theories ever developed, it is also among those with the most striking implications. In particular, General Relativity admits solutions which allow faster than light motion and consequently ... More
Secure Compute-and-Forward Transmission With Artificial Noise and Full-Duplex DevicesJun 14 2016We consider a wiretap channel with an eavesdropper (Eve) and an honest but curious relay (Ray). Ray and the destination (Bob) are full-duplex (FD) devices. Since we aim at not revealing information on the secret message to the relay, we consider the scaled ... More
Dark Radiation and Inflationary FreedomOct 20 2015A relaxed primordial power spectrum (PPS) of scalar perturbations arising from inflation can impact the dark radiation constraints obtained from Cosmic Microwave Background and other cosmological measurements. If inflation produces a non-standard PPS ... More
Half-spectral unidirectional invisibility in non-Hermitian periodic optical structuresOct 19 2015The phenomenon of half-spectral unidirectional invisibility is introduced for one-dimensional periodic optical structures with tailored real and imaginary refractive index distributions in a non-$\mathcal{PT}$-symmetric configuration. The effect refers ... More
Operational Mermin non-locality and All-vs-Nothing argumentsOct 11 2015Contextuality is a key resource in quantum information and the device-independent security of quantum algorithms. In this work, we show that the recently developed, operational Mermin non-locality arguments provide a large, novel family of quantum realisable ... More
Lectures on Integrable Structures in Quantum Field Theory and Massive ODE/IM CorrespondenceJun 09 2016Jul 25 2016This review was born as notes for a lecture given at the YRIS school on integrability in Durham, in the summer of 2015. It deals with a beautiful method, developed in the mid-nineties by V.V. Bazhanov, S.L. Lukyanov and A.B. Zamolodchikov and, as such, ... More
Electroweak radiative corrections at high energiesJan 10 2002This PhD thesis is concerned with one-loop virtual electroweak corrections to arbitrary processes in the high-energy limit. Complete results are presented for the leading and subleading logarithms of large ratios of energy scales to mass scales. These ... More
Highly rotating fluids with vertical stratification for periodic data and vanishing vertical viscosityNov 29 2016We prove that the primitive equations in the periodic domain, with vanishing vertical viscosity can be approximated as $\varepsilon \to 0$ by mean of a suitable limit system. If the initial data has zero horizontal average this convergence is global in ... More
Regularity of solutions of the isoperimetric problem that are close to a smooth manifoldOct 09 2007Oct 18 2015In this work we consider a question in the calculus of variations motivated by riemannian geometry, the isoperimetric problem. We show that solutions to the isoperimetric problem, close in the flat norm to a smooth submanifold, are themselves smooth and ... More
First law of thermodynamics for dynamical apparent horizons and the entropy of Friedmann universesJun 29 2015Aug 10 2015Recently, we have generalized the Bekenstein-Hawking entropy formula for black holes embedded in expanding Friedmann universes. In this letter, we begin the study of this new formula to obtain the first law of thermodynamics for dynamical apparent horizons. ... More
On the Number of Components of the Symplectic Representatives of the Canonical ClassNov 14 2006In this paper we show that there exists a family of simply connected, symplectic 4-manifolds such that the (Poincare dual of the) canonical class admits both connected and disconnected symplectic representatives. This answers a question raised by Fintushel ... More
Geodesic currents and length compactness for automorphisms of free groupsFeb 24 2006Dec 05 2007We prove a compactness theorem for automorphisms of free groups. Namely, we show that the set of automorphisms keeping bounded the length of the uniform current is compact (up to conjugation.) This implies that the spectrum of the length of the images ... More
Computing square-free polarized abelian varieties over finite fieldsMay 25 2018Jan 29 2019We give algorithms to compute isomorphism classes of ordinary abelian varieties defined over a finite field $\mathbb{F}_q$ whose characteristic polynomial (of Frobenius) is square-free and of abelian varieties defined over the prime field $\mathbb{F}_p$ ... More
Stability of $L^\infty$ solutions for hyperbolic systems with coinciding shocks and rarefactionsJun 13 2000We consider a hyperbolic system of conservation laws u_t + f(u)_x = 0 and u(0,\cdot) = u_0, where each characteristic field is either linearly degenerate or genuinely nonlinear. Under the assumption of coinciding shock and rarefaction curves and the existence ... More
Global existence and convergence for non-dimensionalized incompressible Navier-Stokes equations in low Froude number regimeFeb 24 2017Aug 15 2017We prove that the incompressible, density dependent, Navier-Stokes equations are globally well posed in a low Froude number regime. The density is supposed to be increasing in depth and linearized around a stable state. Moreover if the Froude number tends ... More
Entanglement Reactivation in Separable EnvironmentsOct 08 2012Feb 10 2014Combining two entanglement-breaking channels into a correlated-noise environment restores the distribution of entanglement. Surprisingly, this reactivation can be induced by the injection of separable correlations from the composite environment. In any ... More
Symmetric collective attacks for the eavesdropping of symmetric quantum key distributionSep 04 2008Sep 18 2008We consider the collective eavesdropping of the BB84 and six-state protocols. Since these protocols are symmetric in the eigenstates of conjugate bases, we consider collective attacks having the same kind of symmetry. We then show how these symmetric ... More
Comment on "Peres-Horodecki Separability Criterion for Continuous Variable Systems"Nov 29 2005Feb 10 2009The content of this paper is now available as part of arXiv:0902.1502
Steps Towards a Theory of Visual Information: Active Perception, Signal-to-Symbol Conversion and the Interplay Between Sensing and ControlOct 10 2011Aug 31 2012This manuscript describes the elements of a theory of information tailored to control and decision tasks and specifically to visual data. The concept of Actionable Information is described, that relates to a notion of information championed by J. Gibson, ... More
On a set of numbers arising in the dynamics of unimodal mapsAug 04 2003In this paper we initiate the study of the arithmetical properties of a set numbers which encode the dynamics of unimodal maps in a universal way along with that of the corresponding topological zeta function. Here we are concerned in particular with ... More
sin[n Delta t sin (n Delta t1)] as a source of unpredictable dynamicsMar 16 2011Aug 13 2014We investigate the ability of the function sin[n Delta t sin (n Delta t1)], where n is an integer and growing number, to produce unpredictable sequences of numbers. Classical mathematical tools for distinguishing periodic from chaotic or random behaviour, ... More
PT-symmetric laser-absorberAug 31 2010In a recent work, Y.D. Chong et al. [Phys. Rev. Lett. {\bf 105}, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by ... More
A unidirectional invisible PT-symmetric complex crystal with arbitrary thicknessOct 20 2014We introduce a new class of $\mathcal{PT}$-symmetric complex crystals which are almost transparent and one-way reflectionless over a broad frequency range around the Bragg frequency, i.e. unidirectionally invisible, regardless of the thickness $L$ of ... More
Coherent transfer by adiabatic passage in two-dimensional latticesMay 28 2014Coherent tunneling by adiabatic passage (CTAP) is a well-established technique for robust spatial transport of quantum particles in linear chains. Here we introduce two exactly-solvable models where the CTAP protocol can be extended to two-dimensional ... More
PT-symmetric optical superlatticesFeb 13 2014Mar 18 2014The spectral and localization properties of $\mathcal{PT}$-symmetric optical superlattices, either infinitely extended or truncated at one side, are theoretically investigated, and the criteria that ensure a real energy spectrum are derived. The analysis ... More
Photonic realization of the relativistic Kronig-Penney model and relativistic Tamm surface statesFeb 02 2011Photonic analogues of the relativistic Kronig-Penney model and of relativistic surface Tamm states are proposed for light propagation in fibre Bragg gratings (FBGs) with phase defects. A periodic sequence of phase slips in the FBG realizes the relativistic ... More
Non-exponential decay via tunneling in tight-binding lattices and the optical Zeno effectNov 15 2006An exactly-solvable model for the decay of a metastable state coupled to a semi-infinite tight-binding lattice, showing large deviations from exponential decay in the strong coupling regime, is presented. An optical realization of the lattice model, based ... More
Stopping and Time Reversal of Light in Dynamic Photonic Structures via Bloch OscillationsDec 18 2006It is theoretically shown that storage and time-reversal of light pulses can be achieved in a coupled-resonator optical waveguide by dynamic tuning of the cavity resonances without maintaining the translational invariance of the system. The control exploits ... More
Non-Markovian Decay and Lasing Condition in an Optical Microcavity Coupled to a Structured ReservoirNov 10 2006The decay dynamics of the classical electromagnetic field in a leaky optical resonator supporting a single mode coupled to a structured continuum of modes (reservoir) is theoretically investigated, and the issue of threshold condition for lasing in presence ... More
Time Series Forecasting: A Nonlinear Dynamics ApproachJun 18 1999Jun 21 1999The problem of prediction of a given time series is examined on the basis of recent nonlinear dynamics theories. Particular attention is devoted to forecast the amplitude and phase of one of the most common solar indicator activity, the international ... More
Wavelet analysis of solar magnetic strength indicesMay 09 2013Wavelet analysis of different solar activity indices, sunspot numbers, sunspot areas, flare index, magnetic fields, etc., allows us to investigate the time evolution of some specific features of the solar activity and the underlying dynamo mechanism. ... More
Wavelet entropy as a measure of solar cycle complexityMay 16 2000Using wavelet analysis approach, we can derive a measure of the disorder content of solar activity, following the temporal evolution of the so-called wavelet entropy. The interesting feature of this parameter is its ability to extract a dynamical complexity ... More
Time Series Forecasting: A Multivariate Stochastic ApproachJan 27 1999Feb 02 1999This note deals with a multivariate stochastic approach to forecast the behaviour of a cyclic time series. Particular attention is devoted to the problem of the prediction of time behaviour of sunspot numbers for the current 23th cycle. The idea is to ... More
Vacuum and semiclassical gravity: a difficulty and its bewildering significanceSep 18 2007We review a long-standing difficulty in some semiclassical models of vacuum and vacuum decay. Surprisingly enough these models, careless of their transparent formulation, are affected by, both, technical and conceptual issues. After proving some general ... More
Monadic DynamicsJan 19 2015We develop a monadic framework formalising an operational notion of dynamics, seen as the setting and evolution of initial value problems, in general physical theories. We identify in the Eilenberg-Moore category the natural environment for dynamical ... More
Summary: Clusters of Galaxies and the High Redshift Universe Observed in X-RaysJun 26 2001This Meeting featured the recent advancements in our understanding of galaxy clusters and the distant Universe, achieved by the past and new generation of X-ray satellites. I summarize here the main themes that have been discussed: (a) Clusters of galaxies ... More
Blazars: the next gamma-ray view of GLASTAug 21 2003Nov 20 2003Blazars, the extreme family of AGN, can be strong gamma-ray emitters and constitute the largest fraction of identified point sources of EGRET. The next Gamma-ray Large Area Space Telescope (GLAST) is a high energy (30MeV-300GeV) gamma-ray astronomy mission, ... More
Irreducible QCD backgrounds to top searches in semi-leptonic final states at the Next Linear ColliderJan 28 1999At future electron-positron colliders, one of the largest irreducible backgrounds to top searches in the channel `4 jets + lepton + missing energy' comes from QCD events of order $\alpha_s^2$. We compute here such processes exactly at the parton level ... More
The process $e^+e^-\to b\bar bW^+W^-$ at the Next Linear Collider in the Minimal Supersymmetric Standard ModelMay 05 1996The complete matrix element for $e^+e^-\rightarrow b\bar b W^+W^-$ is computed at tree-level within the Minimal Supersymmetric Standard Model. Rates of interest to phenomenological analyses at the Next Linear Collider are given. In particular, we study: ... More
Type IIB construction of flavoured ABJ(M) and fractional M2 branesJul 26 2010May 10 2011We study type IIB brane configurations engineering 3d flavoured ABJ(M) theories with Yang-Mills kinetic terms, which flow to IR fixed points describing M2 branes at a class of toric Calabi-Yau fourfold singularities. The type IIB construction provides ... More
Hadron physics at a neutrino factoryJul 17 2002We review the way intense neutrino beams at the front-end of a muon storage ring can be used to probe the structure of hadrons. Specifically, we discuss how the polarized and unpolarized flavor structure of the nucleon can be disentangled in inclusive ... More
Highlights of Short Baseline Physics at a Neutrino FactorySep 24 2001We review the physics potential for experiments with intense neutrino beams at the front-end of a muon storage ring, stressing the way the spin and flavour structure of neutrino interactions with matter can be used to shed light on the structure of the ... More