Results for "Stefano S. Turzi"

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Viscoelastic nematodynamicsJul 11 2016Nematic liquid crystals exhibit both crystal-like and fluid-like features. In particular, the propagation of an acoustic wave shows an unexpected occurrence of some of the solid-like features at the hydrodynamic level, namely, the frequency-dependent ... More
Tumbling in nematic polymers and liquid crystalsMar 13 2019Most, but not all, liquid crystals tend to align when subject to shear flow, while most nematic polymeric liquid crystals undergo a tumbling instability, where the director rotate with the flow. The reasons of this instability remain elusive, as it is ... More
Determination of the symmetry classes of orientational ordering tensorsFeb 20 2016The orientational order of nematic liquid crystals is traditionally studied by means of the second-rank ordering tensor $\mathbb{S}$. When this is calculated through experiments or simulations, the symmetry group of the phase is not known \emph{a-priori}, ... More
Snap buckling of a confined thin elastic sheetApr 20 2015A growing or compressed thin elastic sheet adhered to a rigid substrate can exhibit a buckling instability, forming an inward hump. Our study shows that the strip morphology depends on the delicate balance between the compression energy and the bending ... More
Liquid relaxation: A new Parodi-like relation for nematic liquid crystalsSep 30 2015Jun 10 2016We put forward a hydrodynamic theory of nematic liquid crystals that includes both anisotropic elasticity and dynamic relaxation. Liquid remodeling is encompassed through a continuous update of the shear-stress free configuration. The low-frequency limit ... More
Growth-induced blisters in a circular tubeNov 27 2013The growth of an elastic film adhered to a confining substrate might lead to the formation of delimitation blisters. Many results have been derived when the substrate is flat. The equilibrium shapes, beyond small deformations, are determined by the interplay ... More
The delamination of a growing elastic sheet with adhesionJul 06 2016We study the onset of delamination blisters in a growing elastic sheet adhered to a flat stiff substrate. When the ends of the sheet are kept fixed, its growth arouses residual stresses that lead to delamination. This instability can be viewed as a discontinuous ... More
Molien series and low-degree invariants for a natural action of ${\bf SO}(3)\wr{\bf Z}_2$Jul 24 2014We investigate the invariants of the $25$-dimensional real representation of the group ${\bf SO}(3)\wr{\bf Z}_2$ given by the left and right actions of ${\bf SO}(3)$ on $5\times 5$ matrices together with matrix transposition; the action on column vectors ... More
Classical Origin of the Spin of Relativistic Pointlike Particles and Geometric interpretation of Dirac SolutionsMar 27 2008Spin of elementary particles is the only kinematic degree of freedom not having classical corre- spondence. It arises when seeking for the finite-dimensional representations of the Lorentz group, which is the only symmetry group of relativistic quantum ... More
Optimized Dynamical Decoupling for Time Dependent HamiltoniansOct 02 2009Mar 16 2010The validity of optimized dynamical decoupling (DD) is extended to analytically time dependent Hamiltonians. As long as an expansion in time is possible the time dependence of the initial Hamiltonian does not affect the efficiency of optimized dynamical ... 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
Contact-induced spin polarization in carbon nanotubesNov 28 2003Motivated by the possibility of combining spintronics with molecular structures, we investigate the conditions for the appearance of spin-polarization in low-dimensional tubular systems by contacting them to a magnetic substrate. We derive a set of general ... More
Constraining the Z' Mass in 331 Models using Direct Dark Matter DetectionJul 30 2013Jul 12 2014We investigate a so-called 331 extension of the Standard Model gauge sector which accommodates neutrino masses and where the lightest of the new neutral fermions in the theory is a viable particle dark matter candidate. In this model, processes mediated ... More
Efficient Coherent Control by Optimized Sequences of Pulses of Finite DurationJun 19 2009Apr 07 2010Reliable long-time storage of arbitrary quantum states is a key element for quantum information processing. In order to dynamically decouple a spin or quantum bit from a dephasing environment, we introduce an optimized sequence of $N$ control pulses of ... More
GeV WIMPs scattering off of OH impurities cannot explain the DAMA signalJan 17 2014May 05 2014In the presence of OH impurities in the DAMA crystals, GeV-scale WIMPs elastically scattering off of hydrogen nuclei with a spin independent cross section of $\sim 10^{-33}\ {\rm cm}^2$ might explain the annual modulation observed by the DAMA experiment, ... More
Localization threshold of Instantaneous Normal Modes from level-spacing statisticsApr 20 2004We study the statistics of level-spacing of Instantaneous Normal Modes in a supercooled liquid. A detailed analysis allows to determine the mobility edge separating extended and localized modes in the negative tail of the density of states. We find that ... More
Orbital-Selective Mottness in Layered Iron Oxychalcogenides: The Case of Na_{2}Fe_{2}OSe_{2}Jul 05 2013Using a combination of th local-density approximtion (LDA) and dynamicla mean-field theory (DMFT) calculations, we explore the correlated electronic structure of a member of the layered Iron oxychalcogenide Na_{2}Fe_{2}OSe_{2}. We find that the parent ... More
Dark Matter and Global SymmetriesAug 26 2015Nov 02 2016General considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. Assuming the validity of such considerations, we derive stringent ... More
Topological phases and topological entropy of two-dimensional systems with finite correlation lengthSep 05 2007Jan 29 2008We elucidate the topological features of the entanglement entropy of a region in two dimensional quantum systems in a topological phase with a finite correlation length $\xi$. Firstly, we suggest that simpler reduced quantities, related to the von Neumann ... More
Non-thermal WIMPs as "Dark Radiation" in Light of ATACAMA, SPT, WMAP9 and PlanckApr 18 2013The Planck and WMAP9 satellites, as well as the ATACAMA and South Pole telescopes, have recently presented results on the angular power spectrum of the comic microwave background. Data tentatively point to the existence of an extra radiation component ... More
The Dark Z' Portal: Direct, Indirect and Collider SearchesDec 18 2013We perform a detailed study of the dark Z' portal using a generic parametrization of the Z'-quarks couplings, both for light (8-15)GeV and heavy (130-1000)GeV dark matter scenarios. We present a comprehensive study of the collider phenomenology including ... More
The equivariant A-twist and gauged linear sigma models on the two-sphereApr 23 2015Sep 22 2015We study two-dimensional $\mathcal{N}=(2,2)$ supersymmetric gauged linear sigma models (GLSM) on the $\Omega$-deformed sphere, $S^2_\Omega$, which is a one-parameter deformation of the $A$-twisted sphere. We provide an exact formula for the $S^2_\Omega$ ... More
Many-body and correlation effects on parametric polariton amplificazion in semiconductor microcavitiesMay 09 2002Very efficient amplification of light-matter waves (polaritons), that are a superposition of cavity photons and excitons [1] has recently been reported[2-11]. The optical gain curve versus the pump power shows a threshold and then saturates to a maximum ... More
Frequency modulated pulses for quantum bits coupled to time-dependent bathsDec 02 2011Feb 08 2012We consider the coherent control of a quantum bit by the use of short pulses with finite duration \tau_p. By shaping the pulse, we perturbatively decouple the dynamics of the bath from the dynamics of the quantum bit during the pulse. Such shaped pulses ... More
Photoluminescence from Microcavities Strongly Coupled to Single Quantum DotsJun 08 2009e study theoretically, the photoluminescence properties of a single quantum dot in a microcavity under incoherent excitation. We propose a microscopic quantum statistical approach providing a Lindblad (thus completely positive) description of pumping ... More
The Hurwitz Enumeration Problem of Branched Covers and Hodge IntegralsSep 15 2000We use algebraic methods to compute the simple Hurwitz numbers for arbitrary source and target Riemann surfaces. For an elliptic curve target, we reproduce the results previously obtained by string theorists. Motivated by the Gromov-Witten potentials, ... More
Localization in one-dimensional chains with Lévy-type disorderDec 05 2014We study Anderson localization of the classical lattice waves in a chain with mass impurities distributed randomly through a power-law relation $s^{-(1+\alpha)}$ with $ s $ as the distance between two successive impurities and $\alpha>0$. This model of ... More
Comparative Study of Nonproportionality and Electronic Band Structures Features in Scintillator MaterialsJul 20 2009The origin of nonproportionality in scintillator materials has been a long standing problem for more than four decades. In this manuscript, we show that, with the help of first principle modeling, the parameterization of the nonproportionality for several ... More
Explaining Dark Matter and $B$ Decay Anomalies with an $L_μ- L_τ$ ModelSep 13 2016We present a dark sector model based on gauging the $L_\mu - L_\tau$ symmetry that addresses anomalies in $b \rightarrow s \mu^+ \mu^-$ decays and that features a particle dark matter candidate. The dark matter particle candidate is a vector-like Dirac ... More
The Fundamental Plane of QSOs and the Relationship Between Host and NucleusFeb 13 2008We present results from an archival study of 70 medium-redshift QSOs observed with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The QSOs have magnitudes M_V <= -23 (total nuclear plus host light) and redshifts $0.06 <= z <= 0.46$. ... More
Semiparametric Slepian-Bangs Formula for Complex Elliptically Symmetric DistributionsJul 24 2018This letter aims at deriving a Semiparametric Slepian-Bangs (SSB) formula for Complex Elliptically Symmetric (CES) distributed data vectors. The Semiparametric Cram\'{e}r-Rao Bound (SCRB), related to the proposed SSB formula, provides a lower bound on ... More
String Landscape and Fermion MassesFeb 18 2019Besides the string scale, string theory has no parameter except some quantized flux values;and the string theory Landscape is generated by scanning over discrete values of all the flux parameters present. We propose that a typical (normalized) probability ... More
Vortex nucleation and flux front propagation in type II superconductorsNov 03 2003We study flux penetration in a disordered type II superconductor by simulations of interacting vortices, using a Monte Carlo method for vortex nucleation. Our results show that a detailed description of the nucleation process yields a correction to the ... More
Explaining Dark Matter and $B$ Decay Anomalies with an $L_μ- L_τ$ ModelSep 13 2016Mar 11 2017We present a dark sector model based on gauging the $L_\mu - L_\tau$ symmetry that addresses anomalies in $b \rightarrow s \mu^+ \mu^-$ decays and that features a particle dark matter candidate. The dark matter particle candidate is a vector-like Dirac ... More
Dirac-Fermionic Dark Matter in $U(1)_X$ ModelsJun 22 2015Sep 28 2015We study a number of $U(1)_X$ models featuring a Dirac fermion dark matter particle. We perform a comprehensive analysis which includes the study of corrections to the muon magnetic moment, dilepton searches with LHC data, as well as direct and indirect ... More
Effect of Black Holes in Local Dwarf Spheroidal Galaxies on Gamma-Ray Constraints on Dark Matter AnnihilationJun 10 2014Oct 28 2014Recent discoveries of optical signatures of black holes in dwarf galaxies indicates that low-mass galaxies can indeed host intermediate massive black holes. This motivates the assessment of the resulting effect on the host dark matter density profile, ... More
Is dislocation flow turbulent in deformed crystals?May 26 2011Jan 18 2012Intriguing analogies were found between a model of plastic deformation in crystals and turbulence in fluids. A study of this model provides remarkable explanations of known experiments and predicts fractal dislocation pattern formation. Further, the challenges ... More
Bending crystals: Emergence of fractal dislocation structuresJan 28 2010Aug 18 2010We provide a minimal continuum model for mesoscale plasticity, explaining the cellular dislocation structures observed in deformed crystals. Our dislocation density tensor evolves from random, smooth initial conditions to form self-similar structures ... More
Quantum-classical correspondence of the Dirac matrices: The Dirac Lagrangian as a Total DerivativeMay 28 2009The Dirac equation provides a description of spin 1/2 particles, consistent with both the principles of quantum mechanics and of special relativity. Often its presentation to students is based on mathematical propositions that may hide the physical meaning ... More
A New Way to Detect Massive Black Holes in Galaxies: The Stellar Remnants of Tidal DisruptionDec 18 2001We point out that the tidal disruption of a giant may leave a luminous (10^35-10^39 ergs/s), hot (10-100 eV) stellar core. The ``supersoft'' source detected by Chandra at the center of M31 may be such a core; whether or not it is, the observations have ... More
Flux front penetration in disordered superconductorsFeb 26 2001We investigate flux front penetration in a disordered type II superconductor by molecular dynamics (MD) simulations of interacting vortices and find scaling laws for the front position and the density profile. The scaling can be understood performing ... More
A catalogue of photometric redshifts for the SDSS-DR9 galaxiesJul 09 2014Accurate photometric redshifts for large samples of galaxies are among the main products of modern multiband digital surveys. Over the last decade, the Sloan Digital Sky Survey (SDSS) has become a sort of benchmark against which to test the various methods. ... More
Extending Fermi-LAT and H.E.S.S. Limits on Gamma-ray Lines from Dark Matter AnnihilationFeb 26 2016Jul 05 2016Gamma-ray lines from dark matter annihilation ($\chi\chi\to \gamma X$, where $X=\gamma,h,Z$) are always accompanied, at lower energies, by a continuum gamma-ray spectrum stemming both from radiative corrections ($X=\gamma$) and from the decay debris of ... More
The Effective HooperonMar 20 2014Nov 14 2014We explore the possibility of explaining a gamma-ray excess in the Galactic Center, originally pointed out by Hooper, collaborators, and other groups, in an effective field theory framework. We assume that dark matter annihilation is mediated by particles ... More
Emergence of entanglement from a noisy environment: The case of polaritonsOct 25 2008Feb 06 2009We show theoretically that polariton pairs with a high degree of polarization entanglement can be produced through parametric scattering. We demonstrate that it can emerge in coincidence experiments, even at low excitation densities where the dynamics ... More
Spin-Up/Spin-Down models for Type Ia SupernovaeFeb 21 2011In the single degenerate scenario for Type Ia supernova (SNeIa), a white dwarf (WD) must gain a significant amount of matter from a companion star. Because the accreted mass carries angular momentum, the WD is likely to achieve fast spin periods, which ... More
On Intrinsic Geometric Stability of ControllerApr 14 2011This work explores the role of the intrinsic fluctuations in finite parameter controller configurations characterizing an ensemble of arbitrary irregular filter circuits. Our analysis illustrates that the parametric intrinsic geometric description exhibits ... More
The Fundamental Plane of QuasarsNov 17 2005We present results from an archival study of 70 medium-redshift QSOs observed with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The QSOs have magnitudes M_V < -23 (total nuclear plus host light) and redshifts 0.06 < z < 0.46. ... More
The Semiparametric Cramér-Rao Bound for Complex Elliptically Symmetric DistributionsJul 23 2018This letter aims at extending the Constrained Semiparametric Cramer-Rao Bound (CSCRB) for the joint estimation of mean vector and scatter matrix of Real Elliptically Symmetric (RES) distributions to Complex Elliptically Symmetric (CES) distributions. ... More
The Small-Scale Dynamo at Low Magnetic Prandtl NumbersDec 25 2012The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude fast amplification processes need to operate. ... More
Dark Matter Complementarity and the Z$^\prime$ PortalJan 14 2015Sep 28 2015Z' gauge bosons arise in many particle physics models as mediators between the dark and visible sectors. We exploit dark matter complementarity and derive stringent and robust collider, direct and indirect constraints, as well as limits from the muon ... More
Properties of the Konishi multiplet in N=4 SYM theoryApr 02 2001We study perturbative and non-perturbative properties of the Konishi multiplet in N=4 SYM theory in D=4 dimensions. We compute two-, three- and four-point Green functions with single and multiple insertions of the lowest component of the multiplet, and ... More
String Landscape and Fermion MassesFeb 18 2019Feb 25 2019Besides the string scale, string theory has no parameter except some quantized flux values; and the string theory Landscape is generated by scanning over discrete values of all the flux parameters present. We propose that a typical (normalized) probability ... More
Connected components of compact matrix quantum groups and finiteness conditionsOct 04 2012Dec 15 2012We introduce the notion of identity component of a compact quantum group and that of total disconnectedness. As a drawback of the generalized Burnside problem, we note that totally disconnected compact matrix quantum groups may fail to be profinite. We ... More
The Cosmological Constant and the Electroweak ScaleDec 12 2018String theory has no parameter except the string scale, so a dynamically compactified solution to 4 dimensional spacetime should determine both the Planck scale and the cosmological constant $\Lambda$. In the racetrack K\"ahler uplift flux compactification ... More
Modulated pulses compensating classical noiseOct 16 2012We consider pulses of finite duration for coherent control in the presence of classical noise. We derive the corrections to ideal, instantaneous pulses for the case of general decoherence (spin-spin relaxation and spin-lattice relaxation) up to and including ... More
Deblocking of interacting particle assemblies: from pinning to jammingApr 24 2003A wide variety of interacting particle assemblies driven by an external force are characterized by a transition between a blocked and a moving phase. The origin of this deblocking transition can be traced back to the presence of either external quenched ... More
On the logarithmic behaviour in N=4 SYM theoryJun 24 1999We show that the logarithmic behaviour seen in perturbative and non perturbative contributions to Green functions of gauge-invariant composite operators in N=4 SYM with SU(N) gauge group can be consistently interpreted in terms of anomalous dimensions ... More
Searching for Secluded Dark Matter with H.E.S.S., Fermi-LAT, and PlanckNov 08 2017Nov 23 2017Short-lived mediators are often used to describe dark matter interactions with Standard Model particles. When the dark matter mass is heavier than the mass of the mediator, it may self-annihilate into short-lived mediators, and in some cases this might ... More
Vortices in low-density neutron matter and cold Fermi gasesMar 15 2019Cold gas experiments can be tuned to achieve strongly-interacting regimes such as that of low-density neutron matter found in neutron stars crusts. We report $T$=0 diffusion Monte Carlo results for the ground state of both spin-1/2 fermions with short ... 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
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
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
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
Nonequilibrium Langevin Approach to Quantum Optics in Semiconductor MicrocavitiesNov 14 2006Oct 16 2007Recently the possibility of generating nonclassical polariton states by means of parametric scattering has been demonstrated. Excitonic polaritons propagate in a complex interacting environment and contain real electronic excitations subject to scattering ... More
Near-field light emission from dark-states inverted exciton occupationsNov 13 2006We theoretically analyze the carrier capture and distribution among the available energy levels of a symmetric semiconductor quantum dot under continuous-wave excitation resonant with the barrier energy levels. At low temperature all the dot level-occupations ... More
Decoherence-Free Emergence of Macroscopic Local Realism for entangled photons in a cavityFeb 11 2005We investigate the influence of environmental noise on polarization entangled light generated by parametric emission in a cavity. By adopting a recently developed separability criterion, we show that: i) self-stimulation may suppress the detrimental influence ... More
Two Years of the X-ray Sky in M31Feb 04 2002We have been monitoring M31 with HRC and ACIS onboard \chandra regularly in the past two years. By combining eight \chandra ACIS-I observations taken between 1999 to 2001, we have identified 204 X-ray sources within the central $\sim 17\arcmin\times17\arcmin$ ... 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
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
Spontaneous Conversion from Virtual to Real Photons in the Ultrastrong Coupling RegimeOct 08 2012May 23 2013We show that a spontaneous release of virtual photon pairs can occur in a quantum optical system in the ultrastrong coupling regime. In this regime, which is attracting interest both in semiconductor and superconducting systems, the light-matter coupling ... More
Light propagation and localization in modulated photonic lattices and waveguidesJul 15 2011We review both theoretical and experimental advances in the recently emerged physics of modulated photonic lattices. Artificial periodic dielectric media, such as photonic crystals and photonic lattices, provide a powerful tool for the control of the ... More
Numerical Algorithm for Pólya Enumeration TheoremDec 13 2014Although the P\'olya enumeration theorem has been used extensively for decades, an optimized, purely numerical algorithm for calculating its coefficients is not readily available. We present such an algorithm for finding the number of unique colorings ... More
A 2D laser rangefinder scans dataset of standard EUR palletsMay 22 2018In the past few years, the technology of automated guided vehicles (AGVs) has notably advanced. In particular, in the field of factory and warehouse automation, different approaches have been presented for detecting and localizing pallets inside warehouses ... More
Extracting Knowledge From Massive Astronomical Data SetsSep 13 2011Sep 21 2011The exponential growth of astronomical data collected by both ground based and space borne instruments has fostered the growth of Astroinformatics: a new discipline laying at the intersection between astronomy, applied computer science, and information ... More
Augury of Darkness: The Low-Mass Dark Z' PortalDec 21 2016Dec 22 2016Dirac fermion dark matter models with heavy $Z^{\prime}$ mediators are subject to stringent constraints from spin-independent direct searches and from LHC bounds, cornering them to live near the $Z^{\prime}$ resonance. Such constraints can be relaxed, ... More
Gas and Stellar Motions and Observational Signatures of Co-Rotating Spiral ArmsApr 09 2014Jun 25 2014We have observed a snapshot of our N-body/Smoothed Particle Hydrodynamics simulation of a Milky Way-sized barred spiral galaxy in a similar way to how we can observe the Milky Way. The simulated galaxy shows a co-rotating spiral arm, i.e. the spiral arm ... More
Naturalness and Dark Matter Properties of the BLSSMJun 05 2017Jun 07 2017In this report, we compare the naturalness and Dark Matter (DM) properties of the Minimal Supersymmetric Standard Model (MSSM) and the $B-L$ Supersymmetric Standard Model (BLSSM), with universality in both cases. We do this by adopting standard measures ... More
$Λ$-enhanced grey molasses on the $D_2$ transition of Rubidium-87 atomsSep 19 2017Sep 20 2017Laser cooling based on dark states, i.e. states decoupled from light, has proven to be effective to increase the phase-space density of cold trapped atoms. Dark-states cooling requires open atomic transitions, in contrast to the ordinary laser cooling ... More
TensorFlow Doing HPCMar 11 2019TensorFlow is a popular emerging open-source programming framework supporting the execution of distributed applications on heterogeneous hardware. While TensorFlow has been initially designed for developing Machine Learning (ML) applications, in fact ... 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