Results for "Andrea Marrella"

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SmartPM: Automatic Adaptation of Dynamic Processes at Run-TimeOct 12 2018The research activity outlined in this PhD thesis is devoted to define a general approach, a concrete architecture and a prototype Process Management System (PMS) for the automated adaptation of dynamic processes at run-time, on the basis of a declarative ... More
Cognitive Business Process Management for Adaptive Cyber-Physical ProcessesFeb 08 2018In the era of Big Data and Internet-of-Things (IoT), all real-world environments are gradually becoming cyber-physical (e.g., emergency management, healthcare, smart manufacturing, etc.), with the presence of connected devices and embedded ICT systems ... More
The TESTMED Project Experience. Process-aware Enactment of Clinical Guidelines through Multimodal InterfacesJul 05 2018Healthcare is one of the largest business segments in the world and is a critical area for future growth. In order to ensure efficient access to medical and patient-related information, hospitals have invested heavily in improving clinical mobile technologies ... More
A User Evaluation of Automated Process Discovery AlgorithmsJun 08 2018Process mining methods allow analysts to use logs of historical executions of business processes in order to gain knowledge about the actual behavior of these processes. One of the most widely studied process mining operations is automated process discovery. ... More
Automated Discovery of Process Models from Event Logs: Review and BenchmarkMay 05 2017Jan 30 2018Process mining allows analysts to exploit logs of historical executions of business processes to extract insights regarding the actual performance of these processes. One of the most widely studied process mining operations is automated process discovery. ... More
Gauge-invariant Green's functions for the bosonic sector of the standard modelDec 18 1998Jun 21 2000There are many applications in gauge theories where the usually employed framework involving gauge-dependent Green's functions leads to considerable problems. In order to overcome the difficulties invariably tied to gauge dependence, we present a manifestly ... More
Equivariant Differential CohomologyOct 21 2015Nov 10 2015The construction of characteristic classes via the curvature form of a connection is one motivation for the refinement of integral cohomology by de Rham cocycles -- known as differential cohomology. We will discuss the analog in the case of a group action ... More
Lipschitz functions with prescribed blowups at many pointsDec 15 2016May 04 2019In this paper we prove generalizations of Lusin-type theorems for gradients due to Giovanni Alberti, where we replace the Lebesgue measure with any Radon measure $\mu$. We apply this to go beyond the known result on the existence of Lipschitz functions ... More
Equivariant characteristic forms in the Cartan model and Borel equivariant cohomologyAug 31 2015Nov 10 2015We show the compatibility of the differential geometric and the topological construction of equivariant characteristic classes for compact Lie groups. Our analysis motivates a differential geometric construction for equivariant characteristic classes ... More
Band-edge BCS-BEC crossover in a two-band superconductor: physical properties and detection parametersJul 11 2014Superconductivity in iron-based, magnesium diborides, and other novel superconducting materials has a strong multi-band and multi-gap character. Recent experiments support the possibillity for a BCS-BEC crossover induced by strong-coupling and proximity ... More
Ethemba Trusted Host EnvironmentMainly Based on AttestationJan 28 2009Ethemba provides a framework and demonstrator for TPM applications.
Thermodynamic properties and thermal correlation lengths of a Hubbard model with bond-charge interactionFeb 27 2004We investigate the thermodynamics of a one-dimensional Hubbard model with bond-charge interaction X using the transfer matrix renormalization group method (TMRG). Numerical results for various quantities like spin and charge susceptibilities, particle ... More
Imbalanced thee-component Fermi gas with attractive interactions: Multiple FFLO-pairing, Bose-Fermi and Fermi-Fermi mixtures versus collapse and phase separationJun 04 2009We present a detailed study of the population imbalanced three-component Hubbard chain with attractive interactions. Such a system can be realized experimentally with three different hyperfine states of ultra cold $^6$Li atoms in an optical lattice. We ... More
Domestic Corpuscular InflatonJun 28 2018The aim of this paper is to provide a more precise description of the paradigm of corpuscular slow-roll inflation, which was previously introduced by Casadio et al. in [1]. Specifically, we start by expanding the Starobinsky theory on a curved background ... More
Classification of maximal transitive prolongations of super-Poincaré algebrasDec 08 2012Jul 22 2014Let $V$ be a complex vector space with a non-degenerate symmetric bilinear form and $\mathbb S$ an irreducible module over the Clifford algebra $Cl(V)$ determined by this form. A supertranslation algebra is a $\mathbb Z$-graded Lie superalgebra $\mathfrak ... More
Super-Poincare' algebras, space-times and supergravities (II)Aug 31 2011The presentation of supergravity theories of our previous paper "Super-Poincare' algebras, space-times and supergravities (I)" is re-formulated in the language of Berezin-Leites-Kostant theory of supermanifolds. It is also shown that the equations of ... More
Numerical analysis for time-dependent advection-diffusion problems with random discontinuous coefficientsFeb 06 2019Subsurface flows are commonly modeled by advection-diffusion equations. Insufficient measurements or uncertain material procurement may be accounted for by random coefficients. To represent, for example, transitions in heterogeneous media, the parameters ... More
Status of sub-GeV Hidden Particle SearchesAug 26 2010Hidden sector particles with sub-GeV masses like hidden U(1) gauge bosons, the NMSSM CP-odd Higgs, and other axion-like particles are experimentally little constrained as they interact only very weakly with the visible sector. For masses below the muon ... More
The electroweak chiral Lagrangian reanalyzedJul 09 1999Oct 26 2000In this paper we reanalyze the electroweak chiral Lagrangian with particular focus on two issues related to gauge invariance. Our analysis is based on a manifestly gauge-invariant approach that we introduced recently. It deals with gauge-invariant Green's ... More
A universal ionization threshold for strongly driven Rydberg statesApr 21 2004We observe a universal ionization threshold for microwave driven one-electron Rydberg states of H, Li, Na, and Rb, in an {\em ab initio} numerical treatment without adjustable parameters. This sheds new light on old experimental data, and widens the scene ... More
Residual Symmetries in the Spectrum of Periodically Driven Alkali Rydberg StatesNov 25 1999We identify a fundamental structure in the spectrum of microwave driven alkali Rydberg states, which highlights the remnants of the Coulomb symmetry in the presence of a non-hydrogenic core. Core-induced corrections with respect to the hydrogen spectrum ... More
Particle-particle ladder based basis-set corrections applied to atoms and molecules using coupled-cluster theoryMar 13 2019We investigate the basis-set convergence of coupled cluster electronic correlation energies using a recently proposed finite basis-set correction technique. The correction is applied to atomic and molecular systems and is based on a diagrammatically decomposed ... More
A Multilevel Monte Carlo Algorithm for Parabolic Advection-Diffusion Problems with Discontinuous CoefficientsFeb 06 2019The Richards' equation is a model for flow of water in unsaturated soils. The coefficients of this (nonlinear) partial differential equation describe the permeability of the medium. Insufficient or uncertain measurements are commonly modeled by random ... More
Lipschitz functions with prescribed blowups at many pointsDec 15 2016In this paper we prove generalizations of Lusin-type theorems for gradients due to Giovanni Alberti, where we replace the Lebesgue measure with any Radon measure $\mu$. We apply this to go beyond the known result on the existence of Lipschitz functions ... More
Inverse Scattering for the Laplace operator with boundary conditions on Lipschitz surfacesJan 26 2019Feb 17 2019We provide a general scheme, in the combined frameworks of Mathematical Scattering Theory and Factorization Method, for inverse scattering for the couple of self-adjoint operators $(\widetilde\Delta,\Delta)$, where $\Delta$ is the free Laplacian in $L^{2}({\mathbb ... More
Tanaka structures modeled on extended Poincaré algebrasJan 03 2012Oct 04 2012Let (V,(.,.)) be a pseudo-Euclidean vector space and S an irreducible Cl(V)-module. An extended translation algebra is a graded Lie algebra m = m_{-2}+m_{-1} = V+S with bracket given by ([s,t],v) = b(v.s,t) for some nondegenerate so(V)-invariant reflexive ... More
Formality of $\mathbb{P}$-objectsSep 19 2017May 06 2019We show that a $\mathbb{P}$-object and simple configurations of $\mathbb{P}$-objects have a formal derived endomorphism algebra. Hence the triangulated category (classically) generated by such objects is independent of the ambient triangulated category. ... More
Particle-particle ladder based basis-set corrections applied to atoms and molecules using coupled-cluster theoryMar 13 2019Mar 14 2019We investigate the basis-set convergence of coupled cluster electronic correlation energies using a recently proposed finite basis-set correction technique. The correction is applied to atomic and molecular systems and is based on a diagrammatically decomposed ... More
Quasi One-Dimensional Charge-Density-Waves at Low TemperaturesFeb 06 2003Dynamic and static properties of the classical Fukuyama-Lee-Rice model and the renormalization and phase diagrams of a related quantum model with phase-slips are studied. In the first part, the phase correlation function is calculated in the weak pinning ... More
Density theorems for rational numbersDec 17 2012Introducing the notion of a rational system of measure preserving transformations and proving a recurrence result for such systems, we give sufficient conditions in order a subset of rational numbers to contain arbitrary long arithmetic progressions.
Defacing the map: Cartographic vandalism in the digital commonsApr 13 2014This article addresses the emergent phenomenon of carto-vandalism, the intentional defacement of collaborative cartographic digital artefacts in the context of volunteered geographic information. Through a qualitative analysis of reported incidents in ... More
Weighted Efficient Domination for $P_5$-Free Graphs in Linear TimeJul 24 2015In a finite undirected graph $G=(V,E)$, a vertex $v \in V$ {\em dominates} itself and its neighbors. A vertex set $D \subseteq V$ in $G$ is an {\em efficient dominating set} ({\em e.d.} for short) of $G$ if every vertex of $G$ is dominated by exactly ... More
An Efficient Probabilistic Context-Free Parsing Algorithm that Computes Prefix ProbabilitiesNov 28 1994We describe an extension of Earley's parser for stochastic context-free grammars that computes the following quantities given a stochastic context-free grammar and an input string: a) probabilities of successive prefixes being generated by the grammar; ... More From Fortran to performance via transformation and substitution rulesMar 26 2015May 16 2015A large amount of numerically-oriented code is written and is being written in legacy languages. Much of this code could, in principle, make good use of data-parallel throughput-oriented computer architectures., a transformation-based programming ... More transformation-based code generation for GPUs and CPUsMay 29 2014Today's highly heterogeneous computing landscape places a burden on programmers wanting to achieve high performance on a reasonably broad cross-section of machines. To do so, computations need to be expressed in many different but mathematically equivalent ... More
CKM Elements from Squark Gluino LoopsMay 19 2009I present results for the finite renormalization of the Cabibbo-Kobayashi-Maskawa (CKM) matrix induced by gluino--squark diagrams in the MSSM with non-minimal sources of flavour violation. Subsequently I derive bounds on the flavour--off--diagonal elements ... More
PLG2: Multiperspective Processes Randomization and Simulation for Online and Offline SettingsJun 28 2015Jul 28 2016Process mining represents an important field in BPM and data mining research. Recently, it has gained importance also for practitioners: more and more companies are creating business process intelligence solutions. The evaluation of process mining algorithms ... More
Thorotrast and in vivo thorium dioxide: numerical simulation of 30 years of alpha radiation absorption by the tissues near a large compact sourceMar 21 2014Background: The epidemiology of the slightly radioactive contrast agent named Thorotrast presents a very long latency period between the injection and the development of the related pathologies. It is an example of the more general problem posed by a ... More
Optomechanical devices, entanglement and teleportationJan 12 2009In this thesis we study continuous variable systems, focusing on optomechanical devices where a laser field interacts with a macroscopic mechanical oscillator through radiation pressure. We consider the optimization problem of quantum teleportation by ... More
Anomalous U(1) and AsymmetryOct 09 2012In the past years many possible extensions of the Standard Model (SM) have been investigated. If one of this model is revealed at the LHC, we will need tools to distinguish it among the many others studied. One possibility to achieve this goal is to utilize ... More
A note one Sobolev type inequalities with p<1 and modified normSep 22 2004A note that points out the possibility to have p<1 in Sobolev type of inequalities by a use of the momomial structure of polynomials or power series. The proof is simple: Triangle angle inequality p*>1, monomial estimate from p* to exponent p<1, then ... More
Nonlinear time-dependent one-dimensional Schroedinger equation with double well potentialDec 05 2002We consider time-dependent Schroedinger equations in one dimension with double well potential and an external nonlinear perturbation. If the initial state belongs to the eigenspace spanned by the eigenvectors associated to the two lowest eigenvalues then, ... More
Heat Kernel Framework for Asset Pricing in Finite TimeNov 05 2012Sep 26 2013A heat kernel approach is proposed for the development of a general, flexible, and mathematically tractable asset pricing framework in finite time. The pricing kernel, giving rise to the price system in an incomplete market, is modelled by weighted heat ... More
Towards a Gauge Invariant Scattering Theory of Cylindrical Gravitational WavesApr 13 2007In this account we investigate an asymptotically flat space-time geometry. In particular, we focus on a pure gravity model with cylindrical symmetry where no matter fields are included. The Einstein-Rosen metric is introduced and the corresponding Einstein ... More
Topics in Open Topological StringsOct 16 2010This thesis is based on some selected topics in open topological string theory which I have worked on during my Ph.D. It comprises an introductory part where I have focused on the points most needed for the later chapters, trading completeness for conciseness ... More
On Uncertainty Quantification in Particle Accelerators ModellingSep 27 2015Feb 17 2016Using a cyclotron based model problem, we demonstrate for the first time the applicability and usefulness of a uncertainty quantification (UQ) approach in order to construct surrogate models for quantities such as emittance, energy spread but also the ... More
Connecting amplitudes in different gauges beyond perturbation theory: a canonical flow approachSep 13 2015Physical quantities in gauge theories have to be gauge-independent. However their evaluation can be greatly simplified by working in particular gauges. Since physical quantities have to be gauge invariant, it is important to establish an approach allowing ... More
Quantum Local Symmetry of the D-Dimensional Non-Linear Sigma Model: A Functional ApproachApr 17 2014We summarize recent progress on the symmetric subtraction of the Non-Linear Sigma Model in $D$ dimensions, based on the validity of a certain Local Functional Equation (LFE) encoding the invariance of the SU(2) Haar measure under local left transformations. ... More
Comments on the Equivalence between Chern-Simons Theory and Topological Massive Yang-Mills Theory in 3DNov 18 2002The classical formal equivalence upon a redefinition of the gauge connection between Chern-Simons theory and topological massive Yang-Mills theory in three-dimensional Euclidean space-time is analyzed at the quantum level within the BRST formulation of ... More
PT-symmetric Deformations of the Korteweg-de Vries EquationJan 11 2007We propose a new family of complex PT-symmetric extensions of the Korteweg-de Vries equation. The deformed equations can be associated to a sequence of non-Hermitian Hamiltonians. The first charges related to the conservation of mass, momentum and energy ... More
A note on the integrability of non-Hermitian extensions of Calogero-Moser-Sutherland modelsNov 08 2005We consider non-Hermitian but PT-symmetric extensions of Calogero models, which have been proposed by Basu-Mallick and Kundu for two types of Lie algebras. We address the question of whether these extensions are meaningful for all remaining Lie algebras ... More
Anti-Hierarchical Growth of Supermassive Black Holes and QSO lifetimesSep 02 2004I present a new method to unveil the history of cosmic accretion and the build-up of Supermassive Black Holes (SMBH) in the nuclei of galaxies, based on observations of the evolving radio and (hard) X-ray luminosity functions of AGN. The fundamental plane ... More
Cosmological evolution of supermassive black holes and AGN: a synthesis model for accretion and feedbackAug 01 2008The growth of supermassive black holes (SMBH) through accretion is accompanied by the release of enormous amounts of energy which can either be radiated away, as happens in quasars, advected into the black hole, or disposed of in kinetic form through ... More
Two New Complete Invariants of von Neumann AlgebrasNov 20 2014We show that the oriented context category and the oriented spectral presheaf are complete invariants of a von Neumann algebra not isomorphic to $\mathbb{C}\oplus\mathbb{C}$ and with no direct summand of type $I_2$.
Geometric remarks on Kalman filtering with intermittent observationsJun 09 2009Sinopoli et al. (TAC, 2004) considered the problem of optimal estimation for linear systems with Gaussian noise and intermittent observations, available according to a Bernoulli arrival process. They showed that there is a "critical" arrival probability ... More
Heavy-flavor transportSep 15 2015Oct 29 2015The formation of a hot deconfined medium (Quark-Gluon Plasma) in high-energy nuclear collisions affects heavy-flavor observables. In the low/moderate-pT range transport calculations allow one to simulate the propagation of heavy quarks in the plasma and ... More
Solvability of rank one $p$-adic differential and $q$-difference equations over the Amice ringMay 05 2015We provide a necessary and sufficient condition for the solvability of a rank one differential (resp. $q$-difference) equation over the Amice's ring. We also extend to that ring a Birkoff decomposition result, originally due to Motzkin.
Challenges and Opportunities for the Next Generation of Photon Regeneration ExperimentsMar 11 2010Photon regeneration experiments searching for signatures of oscillations of photons into hypothetical very weakly interacting ultra-light particles, such as axions, axion-like and hidden-sector particles, have improved their sensitivity considerably in ... More
Prospects for the direct detection of the cosmic neutrino backgroundJan 12 2009The existence of a cosmic neutrino background -- the analogue of the cosmic microwave background -- is a fundamental prediction of standard big bang cosmology. Up to now, the observational evidence for its existence is rather indirect and rests entirely ... More
Supercooled Liquids for PedestriansMar 25 2009When we lower the temperature of a liquid, at some point we meet a first order phase transition to the crystal. Yet, under certain conditions it is possible to keep the system in its metastable phase and to avoid crystallization. In this way the liquid ... More
From Axions to Other WISPsOct 17 2008We illustrate, taking a top-down point of view, how axions and other very weakly interacting sub-eV particles (WISPs) arise in the course of compactification of the extra spatial dimensions in string/M-theory.
Detailed balance as a quantum-group symmetry of Kraus operatorsJun 01 2015Jul 20 2015A unital completely positive map governing the time evolution of a quantum system is usually called a quantum channel, and it can be represented by a tuple of operators which are then referred to as the Kraus operators of the channel. We look at states ... More
The Structure and Dark Halo Core Properties of Dwarf Spheroidal GalaxiesJan 26 2015Jun 22 2015The structure and dark matter halo core properties of dwarf spheroidal galaxies (dSphs) are investigated. A double-isothermal model of an isothermal stellar system, embedded in an isothermal dark halo core provides an excellent fit to the various observed ... More
The Turbulent Interstellar MediumMay 03 2006An overview is presented of the main properties of the interstellar medium. Evidence is summarized that the interstellar medium is highly turbulent, driven on different length scales by various energetic processes. Large-scale turbulence determines the ... More
Complexity in small-scale dwarf spheroidal galaxiesMay 05 2009Our knowledge about the dynamics, the chemical abundances and the evolutionary histories of the more luminous dwarf spheroidal (dSph) galaxies is constantly growing. However, very little is known about the enrichment of the ultra-faint systems recently ... More
Field theory of monochromatic optical beams. II Classical and quantum paraxial fieldsDec 07 2014This work is the second part of an investigation aiming at the study of optical wave equations from a field-theoretic point of view. Here, we study classical and quantum aspects of scalar fields satisfying the paraxial wave equation. First, we determine ... More
Compton Thick AGN: the dark side of the X-ray backgroundMar 30 2004The spectrum of the hard X-ray background records the history of accretion processes integrated over the cosmic time. Several pieces of observational and theoretical evidence indicate that a significant fraction of the energy density is obscured by large ... More
What's wrong with AGN models for the X-ray background ?Mar 29 2000The origin of the hard X-ray background (XRB) as a superposition of unabsorbed and absorbed Active Galactic Nuclei is now widely accepted as the standard model. The identification of faint X-ray sources in ROSAT, ASCA, and BeppoSAX medium-deep surveys ... More
Experimental Tests of the Holographic Entropy BoundNov 14 2003Nov 25 2003Kovtun, Son and Starinets proposed a bound on the viscosity of any fluid in terms of its entropy density. The bound is saturated by maximally supersymmetric theories at strong coupling, but can also easily be challenged experimentally to within a factor ... More
Semiconductor Superlattices: A model system for nonlinear transportJul 10 2001Electric transport in semiconductor superlattices is dominated by pronounced negative differential conductivity. In this report the standard transport theories for superlattices, i.e. miniband conduction, Wannier-Stark-hopping, and sequential tunneling, ... More
Transport in nanostructures: A comparison between nonequilibrium Green functions and density matricesMay 16 2001Stationary electric transport in semiconductor nanostructures is studied by the method of nonequilibrium Green functions. In the case of sequential tunneling the results are compared with density matrix theory, providing almost identical results. Nevertheless, ... More
An unbiased deep search for small-area molecular structuresFeb 09 2006Small-area molecular structures (SAMS) resembling those clumpuscules, proposed by Pfenniger and Combes (1994) as candidate for baryonic dark matter, have recently been detected (Heithausen 2002, 2004) in an area where the shielding is too low for them ... More
Small-area molecular clouds without shieldingAug 29 2002Using the IRAM 30m telescope two molecular structures have been detected which cover very small areas, FWHM<1'. The clouds have velocities of v_lsr~5kms and linewidth of dv~0.8km/s; thus they belong most likely to the Milky Way. Applying standard conversion ... More
Yoctosecond photon pulse generation in heavy ion collisionsFeb 02 2011Heavy ion collisions at RHIC and at the LHC can create the quark-gluon plasma, a state of matter at very high temperatures. Among a plethora of particles that are produced in these collisions, also light is emitted throughout the evolution of the plasma. ... More
Application of Quantum Stochastic Calculus to Feedback ControlAug 07 2013The basic aspects of the Hudson-Parthasarathy quantum stochastic calculus and of the Accardi-Fagnola-Quaegebeur representation free stochastic calculus are presented. The basic features of the stochastic calculus for the square of white noise recently ... More
The MRPC-based ALICE Time-Of-Flight detector: status and performanceMar 27 2012The large Time-Of-Flight (TOF) array is one of the main detectors devoted to charged hadron identification in the mid-rapidity region of the ALICE experiment at the LHC. It allows separation among pions, kaons and protons up to a few GeV/c, covering the ... More
Holographic entropy bound from gravitational Fock space truncationSep 03 2004Oct 20 2004A simplified derivation of Yurtsever's result, which states that the entropy of a truncated bosonic Fock space is given by a holographic bound when the energy of the Fock states is constrained gravitationally, is given for asymptotically flat spacetimes ... More
Results on Jet Spectra and Structure from ALICEOct 23 2012Full jet reconstruction in ALICE uses the combined information from charged and neutral particles. Essentially all jet constituents can be measured with large efficiency down to very low transverse momenta (pT > 150 MeV/c). This has the advantage to introduce ... More
On the stability of the tangent bundle of Fano manifoldsJul 10 1994By using the classification of Fano 3-folds we prove: Let $X$ be Fano 3-fold. Assume that the tangent bundle $T_X$ of $X$ is not stable (i.e. semi-stable or unstable). Then $b_2\geq 2$ and a relative tangent sheaf $T_{X/Y}$ of a contraction $f:X\longrightarrow ... More
On hyperbolicity of SU(2)-equivariant, punctured disc bundles over the complex affine quadricApr 15 2011Mar 07 2012Given a holomorphic line bundle over the complex affine quadric $Q^2$, we investigate its Stein, SU(2)-equivariant disc bundles. Up to equivariant biholomorphism, these are all contained in a maximal one, say $\Omega_{max}$. By removing the zero section ... More
Weak Gravity Conjecture as a Razor Criterium for Exotic D-brane instantonsJul 05 2016Jul 14 2016We discuss implications of Weak gravity conjecture (WGC) for exotic D-brane instantons. In particular, WGC leads to indirect stringent bounds on non-perturbative superpotentials generated by exotic instantons, with many implications for phenomenology: ... More
Spectral homogenization for a Robin-Neumann problemApr 23 2016We consider a Neumann-Robin spectral problem in a perforated domain $\Omeps$. By homogenization techniques we find the suitable homogenized problem and we discuss the asymptotics of eigenpairs, as the size of the perforation tends to zero. Our results ... More
Prescribing metrics on the boundary of AdS 3-manifoldsApr 18 2016Nov 09 2016We prove that given two metrics $g_{+}$ and $g_{-}$ with curvature $\kappa <-1$ on a closed, oriented surface $S$ of genus $\tau\geq 2$, there exists an $AdS$ manifold $N$ with smooth, space-like, strictly convex boundary such that the induced metrics ... More
Spectrophotometric analysis of cometary nuclei from in situ observations (PhD thesis)Mar 27 2015Topic of this work are comets, small and elusive objects that may hold great secrets about the origin of the Solar System and life on Earth, being among the most primitive objects. The method of investigation addressed in this work is the visible and ... More
Ciao? Adios!Nov 05 2007At the "New Horizons in Globular Cluster Astronomy" conference (Padova, June 2002), two members of the VLT globular cluster team presented different views on the importance of heavy-element sedimentation in Population II stars: "The lack of evidence for ... More
Periodic impact motions at resonance of a particle bouncing on spheres and cylindersApr 14 2015We investigate the existence of periodic trajectories of a particle, subject to a central force, which can hit a sphere, or a cylinder. We will provide also a Landesman-Lazer type of condition in the case of a nonlinearity satisfying a double resonance ... More
Double resonance for one-sided superlinear or singular nonlinearitiesSep 29 2015We deal with the problem of existence of periodic solutions for the scalar differential equation x" + f (t, x) = 0 when the asymmetric nonlinearity satisfies a one-sided superlinear growth at infinity. The nonlinearity is asked to be next to resonance ... More
Finite Gyroradius Corrections in the Theory of Perpendicular Diffusion, 1. Suppressed Velocity DiffusionJun 23 2015A fundamental problem in plasma physics, space science, and astrophysics is the transport of energetic particles interacting with stochastic magnetic fields. In particular the motion of particles across a large scale magnetic field is difficult to describe ... More
Perpendicular Diffusion of Energetic Particles in Collisionless PlasmasJan 26 2015A fundamental problem in plasma and astrophysics is the interaction between energetic particles and magnetized plasmas. In the current paper we focus on particle diffusion across the guide magnetic field. It is shown that the perpendicular diffusion coefficient ... More
Automated Parameter Selection for Total Variation Minimization in Image RestorationSep 24 2015Nov 09 2015Algorithms for automatically selecting a scalar or locally varying regularization parameter for total variation models with an $L^{\tau}$-data fidelity term, $\tau\in \{1,2\}$, are presented. The automated selection of the regularization parameter is ... More
Skeletal Representations and ApplicationsJan 29 2013Jun 25 2014When representing a solid object there are alternatives to the use of traditional explicit (surface meshes) or implicit (zero crossing of implicit functions) methods. Skeletal representations encode shape information in a mixed fashion: they are composed ... More
Quantum Spin Models and Extended Conformal AlgebrasMar 16 1995First, an algebraic criterion for integrability is discussed -the so-called `superintegrability'- and some results on the classification of superintegrable quantum spin Hamiltonians based on sl(2) are obtained. Next, the massive phases of the Z_n-chiral ... More
Tensor products of recurrent hypercyclic semigroupsOct 01 2008Oct 26 2008We study tensor products of strongly continuous semigroups on Banach spaces that satisfy the hypercyclicity criterion, the recurrent hypercyclicity criterion or are chaotic.
Convergent sequences in discrete groupsMar 22 2010Aug 03 2012We prove that a finitely generated group contains a sequence of non-trivial elements which converge to the identity in every compact homomorphic image if and only if the group is not virtually abelian.
Real photon structure at an e^+e^- linear colliderAug 10 1999Previous studies of the kinematic coverage for measuring the photon structure function F_2^gamma at a future 500 GeV e^+e^- linear collider are updated using current estimates of luminosities and important detector parameters. The perturbative expansion ... More
The local Gromov-Witten theory of CP^1 and integrable hierarchiesFeb 03 2010May 04 2012In this paper we begin the study of the relationship between the local Gromov-Witten theory of Calabi-Yau rank two bundles over the projective line and the theory of integrable hierarchies. We first of all construct explicitly, in a large number of cases, ... More
Discrete logarithms in curves over finite fieldsDec 23 2007A survey on algorithms for computing discrete logarithms in Jacobians of curves over finite fields.
The complexity of class polynomial computation via floating point approximationsJan 24 2006Jul 25 2008We analyse the complexity of computing class polynomials, that are an important ingredient for CM constructions of elliptic curves, via complex floating point approximations of their roots. The heart of the algorithm is the evaluation of modular functions ... More
Effective rate equations for the over-damped motion in fluctuating potentialsApr 18 2001We discuss physical and mathematical aspects of the over-damped motion of a Brownian particle in fluctuating potentials. It is shown that such a system can be described quantitatively by fluctuating rates if the potential fluctuations are slow compared ... More
Flow equations for band--matricesMar 16 1998Continuous unitary transformations can be used to diagonalize or approximately diagonalize a given Hamiltonian. In the last four years, this method has been applied to a variety of models of condensed matter physics and field theory. With a new generator ... More