Results for "Ugo Moschella"

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de Sitter symmetry of Neveu-Schwarz spinorsApr 28 2016We study the relations between Dirac fields living on the 2-dimensional Lorentzian cylinder and the ones living on the double-covering of the 2-dimensional de Sitter manifold, here identified as a certain coset space of the group $SL(2,R)$. We show that ... More
Infrared surprises in the de Sitter universeOct 17 2012We describe a few unexpected features of de Sitter Quantum Field Theory that have no Minkowskian counterparts. These phenomena show that even when the cosmological constant is tiny a Minkowskian way of fast thinking about de Sitter can lead to mistakes ... More
Fourier analysis and holomorphic decomposition on the one-sheeted hyperboloidNov 27 2003We prove a Cauchy-type integral representation for classes of functions holomorphic in four priviledged tuboid domains of the complexified one-sheeted two-dimensional hyperboloid. From a physical viewpoint, this hyperboloid can be used for describing ... More
Quantum fluctuations in the open universeJul 03 1997We solve a continuing controversy when dealing with density fluctuations in open Friedman-Robertson-Walker universes, on the physical relevance of a class of exponential modes. We show explicitly and rigorously that these modes enter the expansion of ... More
Doubly elliptic strings on the (anti-)de Sitter manifoldMar 13 2013We present a new class of elliptic-like strings on two-dimensional manifolds of constant curvature. Our solutions are related to a class of identities between Jacobi theta functions and to the geometry of the lightcone in one (spacelike) dimension more. ... More
A note on canonical quantization of fields on a manifoldFeb 18 2008Apr 01 2009We propose a general construction of quantum states for linear canonical quantum fields on a manifold, which encompasses and generalizes the "standard" procedures existing in textbooks. Our method provides pure and mixed states on the same footing. A ... More
Quantum fields on curved spacetimes and a new look at the Unruh effectApr 23 2009We describe a new viewpoint on canonical quantization of linear fields on a general curved background that encompasses and generalizes the standard treatment of canonical QFT given in textbooks. Our method permits the construction of pure states and mixed ... More
de Sitter tachyons and related topicsMar 13 2014Mar 24 2014We present a complete study of a family of tachyonic scalar fields living on the de Sitter universe. We show that for an infinite set of discrete values of the negative squared mass the fields exhibit a gauge symmetry and there exists for them a fully ... More
Topological surprises in de Sitter QFT in two-dimensionsJan 30 2019Motivated by the study of soluble models of quantum field theory, we illustrate a new type of topological effect by comparing the constructions of canonical Klein-Gordon quantum fields on the two-dimensional de Sitter spacetime as opposed to its double ... More
Quantum Theory on Lobatchevski SpacesSep 18 2007In this paper we set up a general formalism to deal with quantum theories on a Lobatchevski space, i.e. a spatial manifold that is homogeneous, isotropic and has negative curvature. The heart of our approach is the construction of a suitable basis of ... More
Self-Similar Random Processes and Infinite-Dimensional Configuration SpacesMar 04 2004We discuss various infinite-dimensional configuration spaces that carry measures quasiinvariant under compactly-supported diffeomorphisms of a manifold M corresponding to a physical space. Such measures allow the construction of unitary representations ... More
Analyticity properties and thermal effects for general quantum field theory on de Sitter space-timeJan 29 1998We propose a general framework for quantum field theory on the de Sitter space-time (i.e. for local field theories whose truncated Wightman functions are not required to vanish). By requiring that the fields satisfy a weak spectral condition, formulated ... More
Lifetime of a massive particle in a de Sitter universeDec 18 2006Nov 19 2007We study particle decay in de Sitter space-time as given by first order perturbation theory in an interacting quantum field theory. We show that for fields with masses above a critical mass $m_c$ there is no such thing as particle stability, so that decays ... More
Can the Chaplygin gas be a plausible model for dark energy?Sep 19 2002In this note two cosmological models representing the flat Friedmann Universe filled with a Chaplygin fluid, with or without dust, are analyzed in terms of the recently proposed "statefinder" parameters. Trajectories of both models in the parameter plane ... More
Massless scalar field in two-dimensional de Sitter universeSep 27 2006We study the massless minimally coupled scalar field on a two--dimensional de Sitter space-time in the setting of axiomatic quantum field theory. We construct the invariant Wightman distribution obtained as the renormalized zero--mass limit of the massive ... More
Particle decays and stability on the de Sitter universeDec 18 2008Apr 02 2009We study particle decay in de Sitter space-time as given by first order perturbation theory in a Lagrangian interacting quantum field theory. We study in detail the adiabatic limit of the perturbative amplitude and compute the "phase space" coefficient ... More
Towards a General Theory of Quantized Fields on the Anti-de Sitter Space-TimeNov 28 2001Aug 27 2002We propose a general framework for studying quantum field theory on the anti-de-Sitter space-time, based on the assumption of positivity of the spectrum of the possible energy operators. In this framework we show that the n-point functions are analytic ... More
Scalar tachyons in the de Sitter universeMar 06 2010Apr 14 2010We provide a construction of a class of local and de Sitter covariant tachyonic quantum fields which exist for discrete negative values of the squared mass parameter and which have no Minkowskian counterpart. These quantum fields satisfy an anomalous ... More
Correspondence between Minkowski and de Sitter Quantum Field TheoryJun 04 1999Sep 15 1999In this letter we show that the ``preferred'' Klein-Gordon Quantum Field Theories (QFT's) on a d-dimensional de Sitter spacetime can be obtained from a Klein-Gordon QFT on a (d+1)-dimensional ``ambient'' Minkowski spacetime satisfying the spectral condition ... More
Triangular invariants, three-point functions and particle stability on the de Sitter universeJan 27 2009We study a class of three-point functions on the de Sitter universe and on the asymptotic cone. A blending of geometrical ideas and analytic methods is used to compute some remarkable integrals, on the basis of a generalized star-triangle identity living ... More
Stability properties of some perfect fluid cosmological modelsApr 26 2005Nov 14 2005Flat FRW perfect fluid cosmologies can be reproduced as particular solutions of suitable field theoretical models. Here we investigate the stability of perfect fluid model trajectories with respect to sets of trajectories of the corresponding field models ... More
Ultraviolet phenomena in AdS self-interacting quantum field theoryFeb 08 2018We study the one-loop corrections to the four-point function in the Anti de Sitter space-time for a $\phi^4$ field theory. Our calculation shows the existence of non-local counterterms which however respect the AdS isometry. Our arguments are quite general ... More
Anti de Sitter quantum field theory and a new class of hypergeometric identitiesJul 26 2011We use Anti-de Sitter quantum field theory to prove a new class of identities between hypergeometric functions related to the K\"all\'en-Lehmann representation of products of two Anti-de Sitter two-point functions. A rich mathematical structure emerges. ... More
Ultraviolet phenomena in AdS self-interacting quantum field theoryFeb 08 2018Mar 19 2018We study the one-loop corrections to the four-point function in the Anti de Sitter space-time for a $\phi^4$ field theory. Our calculation shows the existence of non-local counterterms which however respect the AdS isometry. Our arguments are quite general ... More
Cosmology in the Newtonian limitMar 26 2012Numerical N-body simulations of large scale structure formation in the universe are based on Newtonian gravity. However, according to our current understanding, the most correct theory of gravity is general relativity. It is therefore important to understand ... More
Lie algebroid cohomology as a derived functorJun 08 2016Sep 11 2016We show that the hypercohomology of the Chevalley-Eilenberg-de Rham complex of a Lie algebroid L over a scheme with coefficients in an L-module can be expressed as a derived functor. We use this fact to study a Hochschild-Serre type spectral sequence ... More
A time-step approximation scheme for a viscous version of the Vlasov equationDec 16 2016Gomes and Valdinoci have introduced a time-step approximation scheme for a viscous version of Aubry-Mather theory; this scheme is a variant of that of Jordan, Kinderlehrer and Otto. Gangbo and Tudorascu have shown that the Vlasov equation can be seen ... More
Marginals with finite repulsive costFeb 21 2017Nov 30 2018We consider a multimarginal transport problem with repulsive cost, where the marginals are all equal to a fixed probability $\rho \in \mathcal{P}(\mathbb{R}^d)$. We prove that, if the concentration of $\rho$ is less than $1/N$, then the problem has a ... More
Lie algebroid cohomology as a derived functorJun 08 2016Apr 14 2017We show that the hypercohomology of the Chevalley-Eilenberg-de Rham complex of a Lie algebroid L over a scheme with coefficients in an L-module can be expressed as a derived functor. We use this fact to study a Hochschild-Serre type spectral sequence ... More
The Aubry set for a version of the Vlasov equationDec 16 2016We check that several properties of the Aubry set, first proven for finite-dimensional Lagrangians by Mather and Fathi, continue to hold in the case of the infinitely many interacting particles of the Vlasov equation on the circle.
Chaotic motions for a version of the Vlasov equationDec 16 2016We consider a version of the Vlasov equation on the circle under a periodic potential $V(x,t)$ and a repulsing smooth interaction $W$. We suppose that the Lagrangian for the single particle has chaotic orbits; using Aubry-Mather theory and ideas of W. ... More
Prediction of beauty particle masses with the heavy quark effective theory (II)Nov 19 1993The effective theory for heavy quarks has additional symmetries with respect to QCD, which relate charm and beauty hadron masses. Assuming the spectrum of charmed particles, we predicted in a previous work the masses of some beauty particles. The predictions ... More
On the absorption spectrum of noble gases at the arc spectrum limitFeb 08 2005Rydberg spectral lines of an atom are sometimes superimposed on the continuous spectrum of a different configuration. Effects of interaction among different configurations in one of these cases are theoretically investigated, and a formula is obtained ... More
Viscous Aubry-Mather theory and the Vlasov equationDec 16 2016The Vlasov equation models a group of particles moving under a potential $V$; moreover, each particle exerts a force, of potential $W$, on the other ones. We shall suppose that these particles move on the $p$-dimensional torus ${\bf T}^p$ and that the ... More
The stochastic value function on metric measure spacesDec 16 2016Let $(S,d)$ be a compact metric space and let $m$ be a Borel probability measure on $(S,d)$. We shall prove that, if $(S,d,m)$ is a $RCD(K,\infty)$ space, then the stochastic value function satisfies the viscous Hamilton-Jacobi equation, exactly as in ... More
An entropy generation formula on $RCD(K,\infty)$ spacesJul 19 2018J. Feng and T. Nguyen have shown that the solutions of the Fokker-Planck equation in $\R^d$ satisfy an entropy generation formula. We prove that, in compact metric measure spaces with the $RCD(K,\infty)$ property, a similar result holds for curves of ... More
What future for the Anthropocene? A biophysical perspectiveOct 07 2015Oct 09 2015The Anthropocene is a proposed time subdivision of the earth's history correlated to the strong human perturbation of the ecosystem. Much debate is ongoing about what date should be considered as the start of the Anthropocene, but much less on how it ... More
Small-angle physics at the intersecting storage rings forty years laterJun 18 2012No abstract: Hadron-hadron cross-sections at the beginning of the 1970s
Parton densities beyond perturbation theoryFeb 27 1995Non perturbative corrections to deep inelastic scattering are computed.
Consistency and lattice renormalization of the effective theory for heavy quarksApr 20 1993The effective theory describing infinite mass particles with a given velocity, has a great interest in heavy flavor physics. It has the unpleasant characteristic that the energy spectrum is unbounded from below; this fact is the source of the problems ... More
Existence of solutions of the master equation in the smooth caseDec 16 2016We give a different proof of a theorem of W. Gangbo and A. Swiech on the short time existence of solutions of the master equation.
Smoothing operators in multi-marginal Optimal TransportJan 22 2019Mar 25 2019Given $N$ absolutely continuous probabilities $\rho_1, \dotsc, \rho_N$ over $\mathbb{R}^d$ which have Sobolev regularity, and given a transport plan $P$ with marginals $\rho_1, \dotsc, \rho_N$, we provide a universal technique to approximate $P$ with ... More
Chaplygin-like gas and branes in black hole bulksMay 03 2000We explore the possibility to locate a brane in black hole bulks. We study explicitly the cases of BHTZ and Schwarzschild-anti de Sitter (AdS) black holes. Our result is that in these cases branes cannot be supported by brane tension alone and it is necessary ... More
Infinitary $λ$-Calculi from a Linear Perspective (Long Version)Apr 27 2016We introduce a linear infinitary $\lambda$-calculus, called $\ell\Lambda_{\infty}$, in which two exponential modalities are available, the first one being the usual, finitary one, the other being the only construct interpreted coinductively. The obtained ... More
Hilbert schemes of points on some K3 surfaces and Gieseker stable bundlesDec 14 1994By using a Fourier-Mukai transform for sheaves on K3 surfaces we show that for a wide class of K3 surfaces $X$ the punctual Hilbert schemes $\Hilb^n(X)$ can be identified, for all $n\geq 1$, with moduli spaces of Gieseker stable vector bundles on $X$ ... More
Self-improving property of degenerate parabolic equations of porous medium-typeMar 23 2016We show that the gradient of solutions to degenerate parabolic equations of porous medium-type satisfies a reverse H\"older inequality in suitable intrinsic cylinders. We modify the by-now classical Gehring lemma by introducing an intrinsic Calder\'on-Zygmund ... More
From Cutting Planes Algorithms to Compression Schemes and Active LearningAug 12 2015Cutting-plane methods are well-studied localization(and optimization) algorithms. We show that they provide a natural framework to perform machinelearning ---and not just to solve optimization problems posed by machinelearning--- in addition to their ... More
Decays into π+π- of the f0(1370) scalar glueball candidate in pp central exclusive production experimentsApr 24 2018The existence and properties of the f0(1370) scalar meson are rather well established from data of antiproton annihilations at rest. However conflicting results from Central Exclusive Production (CEP) experiments of the last millennium and ignorance of ... More
Time Minimal Trajectories for a Spin 1/2 Particle in a Magnetic FieldDec 09 2005Dec 22 2005In this paper we consider the minimum time population transfer problem for the $z$-component of the spin of a (spin 1/2) particle driven by a magnetic field, controlled along the x axis, with bounded amplitude. On the Bloch sphere (i.e. after a suitable ... More
Mañé's conjectures in codimension oneSep 28 2010We prove Ma\~n\'e's conjectures in the context of codimension one Aubry-Mather theory
Picard group of hypersurfaces in toric 3-foldsNov 03 2010Oct 05 2011We show that the usual sufficient criterion for a generic hypersurface in a smooth projective manifold to have the same Picard number as the ambient variety can be generalized to hypersurfaces in complete simplicial toric varieties. This sufficient condition ... More
Superlocalization formulas and supersymmetric Yang-Mills theoriesOct 18 2003By using supermanifold techniques we prove a generalization of the localization formula in equivariant cohomology which is suitable for studying supersymmetric Yang-Mills theories in terms of ADHM data. With these techniques one can compute the reduced ... More
Gravity of a static massless scalar field and a limiting Schwarzschild-like geometryDec 21 2005We study a set of static solutions of the Einstein equations in presence of a massless scalar field and establish their connection to the Kantowski-Sachs cosmological solutions based on some kind of duality transformations. The physical properties of ... More
Unconfused ultraconservative multiclass algorithmsJun 24 2015We tackle the problem of learning linear classifiers from noisy datasets in a multiclass setting. The two-class version of this problem was studied a few years ago where the proposed approaches to combat the noise revolve around a Per-ceptron learning ... More
A Generic Library for Stencil ComputationsJul 06 2012In this era of diverse and heterogeneous computer architectures, the programmability issues, such as productivity and portable efficiency, are crucial to software development and algorithm design. One way to approach the problem is to step away from traditional ... More
On the use of the theory of dynamical systems for transient problemsNov 01 2014This paper is a preliminary work to address the problem of dynamical systems with parameters varying in time. An idea to predict their behaviour is proposed. These systems are called \emph{transient systems}, and are distinguished from \emph{steady systems}, ... More
Self-improving property of the fast diffusion equationOct 09 2018We show that the gradient of the $m$-power of a solution to a singular parabolic equation of porous medium-type (also known as fast diffusion equation), satisfies a reverse H\"older inequality in suitable intrinsic cylinders. Relying on an intrinsic Calder\'on-Zygmund ... More
What is supertopology?Oct 09 1998We discuss the problem of finding an analogue of the concept of a topological space in supergeometry, motivated by a search for a procedure to compactify a supermanifold along odd coordinates. In particular, we examine the topologies naturally arising ... More
Some Properties of DeGiorgi ClassesApr 26 2016The DeGiorgi classes $[DG]_p(E;\gamma)$, defined in (1.1)${}_{\pm}$ below encompass, solutions of quasilinear elliptic equations with measurable coefficients as well as minima and Q-minima of variational integrals. For these classes we present some new ... More
Holomorphic Cartan geometry on manifolds with numerically effective tangent bundleJan 21 2011Let X be a compact connected Kaehler manifold such that the holomorphic tangent bundle TX is numerically effective. A theorem of Demailly, Peternell and Schenider says that there is a finite unramified Galois covering M --> X, a complex torus T, and a ... More
Filtrations of numerically flat Higgs bundles and curve semistable Higgs bundles on Calabi-Yau manifoldsApr 22 2019We consider Higgs bundles satisfying a notion of numerical flatness (H-nflatness) that was previously introduced, and show that they have Jordan-H\"older filtrations whose quotients are stable, locally free and H-nflat. This is applied to show that curve ... More
Quantum metrology with non-equilibrium steady states of quantum spin chainsDec 05 2014We consider parameter estimations with probes being the boundary driven/dissipated non- equilibrium steady states of XXZ spin 1/2 chains. The parameters to be estimated are the dis- sipation coupling and the anisotropy of the spin-spin interaction. In ... More
Factorization and Effective TheoriesMar 30 1998Apr 01 1998We prove factorization in the decay of a B meson into a D* + jet using the Large Energy Effective Theory. The proof is non perturbative, does not require any gauge fixing and is exact in the limit of a very narrow jet. On the other hand, it is shown that ... More
Performances and robustness of quantum teleportation with identical particlesDec 08 2015When quantum teleportation is performed with truly identical massive particles, indistinguishability allows us to teleport addressable degrees of freedom which do not identify particles, but e.g. orthogonal modes. The key resource of the protocol is a ... More
Quantum teleportation with identical particlesFeb 20 2015Feb 27 2015We study teleportation with identical massive particles. Indistinguishability imposes that the relevant degrees of freedom to be teleported are not particles, but rather addressable orthogonal modes. We discuss the performances of teleportation under ... More
Unconfused Ultraconservative Multiclass AlgorithmsMar 20 2014We tackle the problem of learning linear classifiers from noisy datasets in a multiclass setting. The two-class version of this problem was studied a few years ago by, e.g. Bylander (1994) and Blum et al. (1996): in these contributions, the proposed approaches ... More
Self-adjoint extensions and stochastic completeness of the Laplace-Beltrami operator on conic and anticonic surfacesMay 22 2013Oct 07 2015We study the evolution of the heat and of a free quantum particle (described by the Schr\"odinger equation) on two-dimensional manifolds endowed with the degenerate Riemannian metric $ds^2=dx^2+|x|^{-2\alpha}d\theta^2$, where $x\in \mathbb R$, $\theta\in\mathbb ... More
On the Spherical Hausdorff Measure in Step 2 Corank 2 sub-Riemannian GeometryOct 09 2012In this paper, we consider generic corank 2 sub-Riemannian structures, and we show that the Spherical Hausdorf measure is always a C^1-smooth volume, which is in fact generically C^2- smooth out of a stratified subset of codimension 7. In particular, ... More
On semistable principal bundles over a complex projective manifoldMar 28 2008Let G be a simple linear algebraic group defined over the complex numbers. Fix a proper parabolic subgroup P of G and a nontrivial antidominant character \chi of P. We prove that a holomorphic principal G-bundle E over a connected complex projective manifold ... More
Superselectors: Efficient Constructions and ApplicationsOct 05 2010We introduce a new combinatorial structure: the superselector. We show that superselectors subsume several important combinatorial structures used in the past few years to solve problems in group testing, compressed sensing, multi-channel conflict resolution ... More
On the Hodge conjecture for hypersurfaces in toric varietiesAug 16 2017We show that very general hypersurfaces in odd-dimensional simplicial projective toric varieties verifying a certain combinatorial property satisfy the Hodge conjecture (these include projective spaces). This gives a connection between the Oda conjecture ... More
Computational complexity of non-equilibrium steady states of quantum spin chainsJan 29 2016Mar 07 2016We study non-equilibrium steady states (NESS) of spin chains with boundary Markovian dissipation from the computational complexity point of view. We focus on XX chains whose NESS are matrix product operators (MPO), i.e. with coefficients of a tensor operator ... More
Donagi-Markman cubic for the generalised Hitchin systemAug 30 2013Apr 12 2014Donagi and Markman (1993) have shown that the infinitesimal period map for an algebraic completely integrable Hamiltonian system is encoded in a section of the third symmetric power of the cotangent bundle to the base of the system. For the ordinary Hitchin ... More
Self-improving property of degenerate parabolic equations of porous medium-typeMar 23 2016Jun 13 2017We show that the gradient of solutions to degenerate parabolic equations of porous medium-type satisfies a reverse H\"older inequality in suitable intrinsic cylinders. We modify the by-now classical Gehring lemma by introducing an intrinsic Calder\'on-Zygmund ... More
A Boundary Estimate for Degenerate Parabolic Diffusion EquationsJul 17 2018We prove an estimate on the modulus of continuity at a boundary point of a cylindrical domain for local weak solutions to degenerate parabolic equations of $p$-laplacian type. The estimate is given in terms of a Wiener-type integral, defined by a proper ... More
Symbolic and Asynchronous Semantics via Normalized CoalgebrasMar 02 2011May 13 2011The operational semantics of interactive systems is usually described by labeled transition systems. Abstract semantics (that is defined in terms of bisimilarity) is characterized by the final morphism in some category of coalgebras. Since the behaviour ... More
A model for next-to-leading order threshold resummed form factorsJul 20 2004Nov 23 2004We present a model for next-to-leading order resummed threshold form factors based on a time-like coupling recently introduced in the framework of small x physics. Improved expressions for the form factors in N-space are obtained which are not plagued ... More
The structure function of semi-inclusive heavy flavour decays in field theoryMar 15 2000Sep 20 2000We consider the decay of a heavy flavour into an inclusive hadronic state X of invariant mass m_X small with respect to its energy E_X, m_X << E_X. The electron spectrum and the hadronic mass distribution in semileptonic b -> u decays, or the photon spectrum ... More
Resonance of Minimizers for $n$-level Quantum Systems with an Arbitrary CostAug 20 2003Jan 13 2004We consider an optimal control problem describing a laser-induced population transfer on a $n$-level quantum system. For a convex cost depending only on the moduli of controls (i.e. the lasers intensities), we prove that there always exists a minimizer ... More
Exactness of the Annealed and the Replica Symmetric Approximations for Random HeteropolymersApr 11 2000We study a heteropolymer model with random contact interactions introduced some time ago as a simplified model for proteins. The model consists of self-avoiding walks on the simple cubic lattice, with contact interactions between nearest neighbor pairs. ... More
Phase Transitions of Single Semi-stiff Polymer ChainsMay 19 1997We study numerically a lattice model of semiflexible homopolymers with nearest neighbor attraction and energetic preference for straight joints between bonded monomers. For this we use a new algorithm, the "Pruned-Enriched Rosenbluth Method" (PERM). It ... More
Renormalons and confinementMar 02 1995Mar 10 1995We compute the renormalon ambiguity of the static potential, in the limit of a large number of flavors. An extrapolation of the QED result to QCD implies that the large distance behavior of the quark potential is arbitrary in perturbation theory, as there ... More
The maximum penalty criterion for ridge regression: application to the calibration of the force constant in elastic network modelsDec 28 2015Multivariate regression is a widespread computational technique that may give meaningless results if the explanatory variables are too numerous or highly collinear. Tikhonov regularization, or ridge regression, is a popular approach to address this issue. ... More
Sample-Based Learning Model Predictive Control for Linear Uncertain SystemsApr 12 2019We present a sample-based Learning Model Predictive Controller (LMPC) for constrained uncertain linear systems subject to bounded additive disturbances. The proposed controller builds on earlier work on LMPC for deterministic systems. First, we introduce ... More
The Laplace-Beltrami operator in almost-Riemannian GeometryMay 24 2011Two-dimensional almost-Riemannian structures are generalized Riemannian structures on surfaces for which a local orthonormal frame is given by a Lie bracket generating pair of vector fields that can become collinear. Generically, the singular set is an ... More
Fast and accurate annotation of short texts with Wikipedia pagesJun 17 2010Jul 28 2010We address the problem of cross-referencing text fragments with Wikipedia pages, in a way that synonymy and polysemy issues are resolved accurately and efficiently. We take inspiration from a recent flow of work [Cucerzan 2007, Mihalcea and Csomai 2007, ... More
Time Optimal Synthesis for Left--Invariant Control Systems on SO(3)Feb 23 2005Consider the control system given by $\dot x=x(f+ug)$, where $x\in SO(3)$, $|u|\leq 1$ and $f,g\in so(3)$ define two perpendicular left-invariant vector fields normalized so that $\|f\|=\cos(\al)$ and $\|g\|=\sin(\al)$, $\al\in ]0,\pi/4[$. In this paper, ... More
On semistable principal bundles over a complex projective manifold, IISep 25 2009Let (X, \omega) be a compact connected Kaehler manifold of complex dimension d and E_G a holomorphic principal G-bundle on X, where G is a connected reductive linear algebraic group defined over C. Let Z (G) denote the center of G. We prove that the following ... More
Projective Reeds-Shepp car on $S^2$ with quadratic costMay 30 2008Fix two points $x,\bar{x}\in S^2$ and two directions (without orientation) $\eta,\bar\eta$ of the velocities in these points. In this paper we are interested to the problem of minimizing the cost $$ J[\gamma]=\int_0^T g_{\gamma(t)}(\dot\gamma(t),\dot\gamma(t))+ ... More
Invariant Carnot-Caratheodory metrics on $S^3$, $SO(3)$, $SL(2)$ and lens spacesSep 25 2007Jan 24 2008In this paper we study the invariant Carnot-Caratheodory metrics on $SU(2)\simeq S^3$, $SO(3)$ and $SL(2)$ induced by their Cartan decomposition and by the Killing form. Beside computing explicitly geodesics and conjugate loci, we compute the cut loci ... More
Cohomology of skew-holomorphic Lie algebroidsMar 09 2010Sep 02 2010We introduce the notion of skew-holomorphic Lie algebroid on a complex manifold, and explore some cohomologies theories that one can associate to it. Examples are given in terms of holomorphic Poisson structures of various sorts.
Sharp Regularity for Weak Solutions to the Porous Medium EquationJul 23 2016Let $u$ be a nonnegative, local, weak solution to the porous medium equation for $m\ge2$ in a space-time cylinder $\Omega_T$. Fix a point $(x_o,t_o)\in\Omega_T$: if the average \[ a{\buildrel\mbox{def}\over{=}}\frac1{|B_r(x_o)|}\int_{B_r(x_o)}u(x,t_o)\,dx>0, ... More
Q-factorial Laurent ringsAug 20 2011Dolgachev proved that, for any field k, the ring naturally associated to a generic Laurent polynomial in d variables, $d \geq 4$, is factorial. We prove a sufficient condition for the ring associated to a very general complex Laurent polynomial in d=3 ... More
The Noether-Lefschetz locus of surfaces in toric threefoldsAug 08 2015Jul 24 2017The Noether-Lefschetz theorem asserts that any curve in a very general surface $X$ in $\mathbb P^3$ of degree $d \geq 4$ is a restriction of a surface in the ambient space, that is, the Picard number of $X$ is $1$. We proved previously that under some ... More
Moduli of framed sheaves on projective surfacesJun 08 2009Sep 22 2009We show that there exists a fine moduli space for torsion-free sheaves on a projective surface, which have a "good framing" on a big and nef divisor. This moduli space is a quasi-projective scheme. This is accomplished by showing that such framed sheaves ... More
Quasi-periodic motions in a special class of dynamical equations with dissipative effects: a pair of detection methodsJan 03 2014Jul 18 2014We consider a particular class of equations of motion, generalizing to n degrees of freedom the "dissipative spin--orbit problem", commonly studied in Celestial Mechanics. Those equations are formulated in a pseudo-Hamiltonian framework with action-angle ... More
Learning Model Predictive Control for Iterative TasksSep 06 2016A Learning Model Predictive Controller (LMPC) for iterative tasks is presented. The controller is reference-free and is able to improve its performance by learning from previous iterations. A safe set and a terminal cost function are used in order to ... More
Declining trends of healthy life years expectancy (HLYE) in EuropeNov 15 2013Dec 29 2013We examine the trends in Healthy Life Years Expectancy (HLYE) at birth during the past few decades in Europe. We observe that several European countries show a significant drop in HLYE at birth starting from 2003; interrupting what had been a previous ... More
Mapping Fusion and Synchronized Hyperedge Replacement into Logic ProgrammingApr 13 2005Jan 15 2006In this paper we compare three different formalisms that can be used in the area of models for distributed, concurrent and mobile systems. In particular we analyze the relationships between a process calculus, the Fusion Calculus, graph transformations ... More
Long distance effects in semi-inclusive B decaysSep 28 2006We discuss some issues on factorization of long distance effects for semi-inclusive B decay spectra in full QCD and in the effective theory.