Results for "Fabio Bernardoni"

total 3649took 0.11s
Mapping the geometry of the F4 groupMay 28 2007Oct 01 2007In this paper we present a construction of the compact form of the exceptional Lie group F4 by exponentiating the corresponding Lie algebra f4. We realize F4 as the automorphisms group of the exceptional Jordan algebra, whose elements are 3 x 3 hermitian ... More
Heavy-light mesons in the epsilon-regimeOct 14 2009We study the finite-size scaling of heavy-light mesons in the static limit. We compute two-point functions of chiral current densities as well as pseudoscalar densities in the epsilon-regime of heavy meson Chiral Perturbation Theory (HMChPT). As expected, ... More
Finite-size scaling of heavy-light mesonsOct 14 2009We study the finite-size scaling of heavy-light mesons in the static limit. The most relevant effects are due to the pseudo-Goldstone boson cloud. In the HMChPT framework we compute two-point functions of left current densitities as well as pseudoscalar ... More
Determination of the Wilson ChPT low energy constant c_2Nov 18 2011Following a suggestion by Aoki and B\"ar, c2 can be extracted by analyzing volume effects in 2-pion states. To this end we consider renormalized ratios of four point to two point correlation functions. We present the results from various CLS lattices, ... More
Mapping the geometry of the E6 groupOct 01 2007In this paper we present a construction for the compact form of the exceptional Lie group E6 by exponentiating the corresponding Lie algebra e6, which we realize as the the sum of f4, the derivations of the exceptional Jordan algebra J3 of dimension 3 ... More
Exploring the chiral regime of $N_f=2$ QCD with mixed actionsNov 17 2010We report on our simulations with Neuberger valence fermions on CLS $N_f=2$ configurations with non-perturbatively $O(a)$-improved Wilson sea quarks. We consider the matching of QCD to ChPT in the so called mixed-regime in which the sea quarks are in ... More
Light quark correlators in a mixed-action setupOct 05 2011We report our progress in simulating Neuberger valence fermions on N_f=2 Wilson O(a)-improved sea quarks. We compute correlators with valence quark masses both in the p- and in the epsilon-regime, and we match the results with the predictions of the Chiral ... More
Precision lattice QCD computation of the $B^*Bπ$ couplingApr 28 2014The static $B^{*}B\pi$ coupling, $\hat{g}_\chi$, a low energy constant in the leading order heavy meson chiral Lagrangian, is determined using $N_\mathrm{f} = 2$ lattice QCD. We use CLS ensembles with lattice spacings and pion masses down to $a = 0.05\mathrm{fm}$ ... More
Probing the chiral regime of Nf=2 QCD with mixed actionsAug 11 2010May 31 2011We report on our first experiences with a mixed action setup with overlap valence quarks and non-perturbatively O(a) improved Wilson sea quarks. For the latter we employ CLS Nf=2 configurations with light sea quark masses at small lattice spacings. Exact ... More
Form factors for $\mathrm B_\mathrm s \to \mathrm K \ell ν$ decays in Lattice QCDNov 14 2014We present the current status of the computation of the form factor $f_+ (q^2)$ for the semi-leptonic decay $\mathrm B_\mathrm s \to \mathrm K \ell \nu$ by the ALPHA collaboration. We use gauge configurations which were generated as part of the Coordinated ... More
Continuum limit of the leading order HQET form factor in $B_s \to K\ellν$ decaysJan 17 2016Jun 02 2016We discuss the computation of form factors for semi-leptonic decays of $\rm B$-, $\rm B_s$- mesons in lattice QCD. Considering in particular the example of the static $\rm B_s$ form factors we demonstrate that after non-perturbative renormalization the ... More
Extraction of bare Form Factors for $\mathrm B_\mathrm s \to \mathrm K \ell ν$ Decays in non-perturbative HQETMar 14 2019We discuss the extraction of the ground state $\langle \mathrm{K} ({\bf p})|V_\mu(0)|\mathrm{B} ({\bf 0})\rangle$ matrix elements from Euclidean lattice correlation functions. The emphasis is on the elimination of excited state contributions. Two typical ... More
B $\to$ $π$ form factor with 2 flavours of $O(a)$ improved Wilson quarksOct 12 2012The determinations of $|V_{\rm ub}|$ from the exclusive branching ratios of $B\to \tau \nu$ and $B \to \pi l \nu$ tend to show a tension at the level of $3\sigma$ \cite{Beringer:1900zz}. On the theoretical side they depend on the lattice computation of ... More
Finite-size scaling for the left-current correlator with non-degenerate quark massesJul 26 2007We study the volume dependence of the left-current correlator with non-degenerate quark masses to next-to-leading order in the chiral expansion. We consider three possible regimes: all quark masses are in the $\epsilon$-regime, all are in the $p$-regime ... More
B-meson spectroscopy in HQET at order 1/mMay 13 2015Sep 02 2015We present a study of the B spectrum performed in the framework of Heavy Quark Effective Theory expanded to next-to-leading order in 1/m and non-perturbative in the strong coupling. Our analyses have been performed on Nf=2 lattice gauge field ensembles ... More
B-physics from non-perturbatively renormalized HQET in two-flavour lattice QCDOct 24 2012We report on the ALPHA Collaboration's lattice B-physics programme based on N_f=2 O(a) improved Wilson fermions and HQET, including all NLO effects in the inverse heavy quark mass, as well as non-perturbative renormalization and matching, to fix the parameters ... More
On a mathematical relation between the Eigen model and the asexual Wright-Fisher modelFeb 01 2011We show that the Eigen model and the asexual Wright-Fisher model can be obtained as different limit cases of a unique stochastic model. This derivation makes clear which are the exact differences between these two models. The two key concepts introduced ... More
Massless scalar free Field in 1+1 dimensions, II: Net Cohomology and Completeness of Superselection SectorsNov 28 2008May 06 2010As an application of Roberts' cohomology (net cohomology), we prove the completeness of the DHR sectors of the local observables of the model in the title, detailed in [8]. This result is achieved via the triviality of the net 1-cohomology, with values ... More
Tunable Flux Qubit manipulated by fast pulses: operating requirements, dissipation and decoherenceFeb 20 2006A double SQUID manipulated by fast magnetic flux pulses can be used as a tunable flux qubit. In this paper we study the requirements for the qubit operation, and evaluate dissipation and decoherence due to the manipulation for a typical system. Furthermore, ... More
Dipole-dipole interactions in protein-protein complexes: a quantum mechanical study of the ubiquitin-Dsk2 complexAug 14 2013Quantum mechanical calculations are performed on the proteins that constitute the ubiquitin-Dsk2 complex whose atomic structure has been experimentally determined by NMR spectroscopy (PDB id 1WR1). The results indicate that the dipole moment vectors of ... More
Protein conformational dynamics and electronic structureAug 18 2013Quantum mechanical calculations are performed on 116 conformers of the protein ubiquitin (Lange et al., Science 2008, 320, 1471-1475). The results indicate that the heat of formation (HOF), dipole moment, energy of the frontier orbitals HOMO and LUMO, ... More
A factorization method for q-Racah polynomialsJan 10 2011Jul 14 2011We develop a factorization method for q-Racah polynomials. It is inspired to the approach to q-Hahn polynomials based on the q-Johnson scheme but we do not use association scheme theory nor Gel'fand pairs, but only manipolation of q-difference operators. ... More
FreeIMU: An Open Hardware Framework for Orientation and Motion SensingMar 20 2013Orientation and Motion Sensing are widely implemented on various consumer products, such as mobile phones, tablets and cameras as they enable immediate interaction with virtual information. The prototyping phase of any orientation and motion sensing capable ... More
Condensation of gauge interacting mass-less fermionsJan 28 2004A single mass-less fermionic field with an abelian U(1) gauge interaction (electrodynamics of a mass-less Dirac fermion) is studied by a variational method. Even without the insertion of any extra interaction the vacuum is shown to be unstable towards ... More
A Truly Minimal Left-Right Symmetric Extension of the Standard ModelJul 25 2003By invoking the existence of a general custodial O(2) symmetry, a minimal Left-Right symmetric model based on the gauge group G=SU(2)L SU(2)R U(1)BL is shown to require the existence of only two physical Higgs bosons. The lighter Higgs is predicted to ... More
Low Dimensional Ordering on a Lattice ModelJan 08 1997A simple d-dimensional lattice model is proposed, incorporating some degree of frustration and thus capable of describing some aspects of molecular orientation in covalently bound molecular solids. For d=2 the model is shown to be equivalent to the standard ... More
The Monge problem in Wiener SpaceMar 14 2011Mar 24 2011We address the Monge problem in the abstract Wiener space and we give an existence result provided both marginal measures are absolutely continuous with respect to the infinite dimensional Gaussian measure {\gamma}.
Particle production in DIS off a shockwave in AdSDec 09 2009Sep 01 2010Within the AdS/CFT correspondence, the shockwave metric has been widely used as a gravity dual for a fast moving nucleus. Here we propose a picture for particle production in deep inelastic scattering off a shockwave with the projectile represented by ... More
Massive stars in the nuclei and arms of spiralsMay 09 2008Many of the properties of massive stars in external galaxies, such as chemical compositions, mass functions, and ionizing fluxes, can be derived from the study of the associated clouds of ionized gas. Moreover, the signatures of Wolf-Rayet stars are often ... More
Monoids and Maximal CodesAug 18 2011In recent years codes that are not Uniquely Decipherable (UD) are been studied partitioning them in classes that localize the ambiguities of the code. A natural question is how we can extend the notion of maximality to codes that are not UD. In this paper ... More
A categorical semantic for the Typed Epsilon CalculusSep 08 2014We show that every boolean category satisfying AC provides a categorical semantic of the typed Epsilon calculus.
Incommensurability effects on dipolar bosons in optical latticesOct 29 2015We present a study that investigated a quantum dipolar gas in continuous space where a potential lattice was imposed. Employing exact quantum Monte Carlo techniques, we analysed the ground state properties of the scrutinised system, varying the lattice ... More
A quantum-like view to a generalized two players gameMar 03 2015This paper consider the possibility of using some quantum tools in decision making strategies. In particular, we consider here a dynamical open quantum system helping two players, $\G_1$ and $\G_2$, to take their decisions in a specific context. We see ... More
Perturbation theory of non-perturbative QCDJul 20 2015Perturbation theory is shown to be working in the IR limit of pure SU(3) Yang-Mills theory in Landau gauge by an unconventional setting of the perturbative expansion. A dynamical mass is predicted for the gluon and the lattice data are reproduced fairly ... More
The very-extended tromboneJan 11 2010Mar 24 2010Starting from the very-extended Kac-Moody algebra $E_{11}$, we consider the algebra $E_{11,D}^{local}$, obtained by adding to the non-negative level $E_{11}$ generators the $D$-dimensional momentum operator and an infinite set of additional generators ... More
The ERC ENUBET Project: high precision neutrino flux measurements in conventional neutrino beamsApr 29 2017The challenges of precision neutrino physics require measurements of absolute neutrino cross sections at the GeV scale with exquisite (1%) precision. This precision is presently limited by the uncertainties on neutrino flux at the source; their reduction ... More
Visions of a generalized probability theoryOct 18 2018In this Book we argue that the fruitful interaction of computer vision and belief calculus is capable of stimulating significant advances in both fields. From a methodological point of view, novel theoretical results concerning the geometric and algebraic ... More
Vocal Access to a Newspaper Archive: Design Issues and Preliminary InvestigationDec 10 1998This paper presents the design and the current prototype implementation of an interactive vocal Information Retrieval system that can be used to access articles of a large newspaper archive using a telephone. The results of preliminary investigation into ... More
Sheafification functors and Tannaka's reconstructionSep 14 2014We introduce "sheafification" functors from categories of (lax monoidal) linear functors to cat- egories of quasi-coherent sheaves (of algebras) of stacks. They generalize the homogeneous sheafification of graded modules for projective schemes and have ... More
Degeneracy loci of twisted differential forms and linear line complexesDec 17 2014We prove that the Hilbert scheme of degeneracy loci of pairs of global sections of Omega(2), the twisted cotangent bundle on P^(n-1), is unirational and dominated by the Grassmannian of lines in the projective space of skew-symmetric forms over a vector ... More
A Luenberger-style Observer for Robot Manipulators with Position MeasurementsJul 04 2005This paper presents a novel Luenberger-style observer for robot manipulators with position measurements. Under the assumption that the state evolutions that are to be observed have bounded velocities, it is shown that the origin of the observation error ... More
A note on optimization in $\mathbb{R}^n$Feb 23 2019In this article, we develop an algorithm suitable for constrained optimization in $\mathbb{R}^n$. The results are developed through standard tools of n-dimensional real analysis and basic concepts of optimization. Indeed, the well known Banach fixed point ... More
Quantization of Poisson groups -- IIApr 10 1996May 08 2017Let $ G^\tau $ be a connected simply connected semisimple algebraic group, endowed with generalized Sklyanin-Drinfeld structure of Poisson group; let $ H^\tau $ be its dual Poisson group. By means of Drinfeld's double construction and dualization via ... More
On the one fluid limit for vortex sheetAug 24 2009We consider the interface problem between two incompressible and inviscid fluids in the presence of surface tension. Following the geometric approach of [Shatah,J.;Zeng,C. A priori estimates for Fluid Interface Problems. CPAM, vol.16, no.6, June 2008] ... More
On the limit as the surface tension and density ratio tend to zero for the two-phase Euler equationsDec 17 2009Mar 06 2011We consider the free-boundary motion of two perfect incompressible fluids with different densities $\rho_+$ and $\rho_-$, separated by a surface of discontinuity along which the pressure experiences a jump proportional to the mean curvature by a factor ... More
The global quantum duality principle: theory, examples, applicationsAug 02 2001Oct 04 2012The "quantum duality principle" states that a quantisation of a Lie bialgebra provides also a quantisation of the dual formal Poisson group and, conversely, a quantisation of a formal Poisson group yields a quantisation of the dual Lie bialgebra as well. ... More
The global quantum duality principleDec 22 1999May 04 2017Let R be an integral domain, let a non-zero h in R be such that k := R/hR is a field, and let HA be the category of torsionless (or flat) Hopf algebras over R. We call H in HA a "quantized function algebra" (=QFA), resp. "quantized restricted universal ... More
On the methodologies for the assessment of the impact of parameters in acoustophoretic separation devicesApr 20 2019In this communication I reconcile the kinematic method illustrated by some authors~\cite{yang2018,vitali2018} in studying the impact of system and suspension parameters on acoustophoretic separations with the statistical method formerly proposed by Garofalo~\cite{garofalo2014,garofalo2014_2} ... More
Modified scattering for the Boson Star EquationAug 29 2013We consider the question of scattering for the boson star equation in three space dimensions. This is a semi-relativistic Klein-Gordon equation with a cubic nonlinearity of Hartree type. We combine weighted estimates, obtained by exploiting a special ... More
Decomposition of geodesics in the Wasserstein space and the globalization propertySep 26 2012Aug 20 2013We will prove a decomposition for Wasserstein geodesics in the following sense: let $(X,d,m)$ be a non-branching metric measure space verifying $\mathsf{CD}_{loc}(K,N)$ or equivalently $\mathsf{CD}^{*}(K,N)$. We prove that every geodesic $\mu_{t}$ in ... More
Heavy-flavour production in pp collisions and correlations in pp and p-Pb collisions measured with ALICE at the LHCSep 27 2016Thanks to its excellent tracking and particle identification performance, the ALICE detector is capable of measuring D mesons at central rapidity via their hadronic decay channels down to very low transverse momentum. We show an extension of the prompt ... More
A non trivial extension of the two-dimensional Ising model: the d-dimensional "molecular" modelMay 24 2000A recently proposed molecular model is discussed as a non-trivial extension of the Ising model. For d=2 the two models are shown to be equivalent, while for d>2 the molecular model describes a peculiar second order transition from an isotropic high temperature ... More
A variational study of bound states in the Higgs modelAug 03 2000The possible existence of Higgs-Higgs bound states in the Higgs sector of the Standard Model is explored using the |hh>+|hhh> variational ansatz of Di Leo and Darewych. The resulting integral equations can be decoupled exactly, yielding a one-dimensional ... More
Measuring Chemical Abundances in Extragalactic Metal-Rich HII RegionsAug 19 2006The analysis of metal-rich HII regions has a profound impact on the calibration of abundance diagnostics widely used to measure the chemical content of star-forming galaxies, both locally and at high redshift. I review the main difficulties that affect ... More
Clues on the rejuvenation of the S0 galaxy NGC 404 from the chemical abundance of its outer diskJun 13 2013The oxygen abundance of the outer disk of the nearby S0 galaxy NGC 404, a prototypical early-type galaxy with extended star formation, has been derived from the analysis of HII region spectra. The high mean value found, 12+log(O/H)=8.6 \pm 0.1, equivalent ... More
Quarkonium Decays and Production in NRQCDJul 02 2000Some examples of the most recent applications of the NRQCD factorization approach to quarkonium phenomenology are presented. In the first part of the talk the NLO calculations for $\chicj$ and $\Upsilon$ decays rates are compared to the data and the results ... More
Invariant bipartite random graphs on $\mathbb{R}^d$Feb 23 2012Suppose that red and blue points occur in $\mathbb{R}^d$ according to two simple point process with finite intensities $\lambda_{\mathcal{R}}$ and $\lambda_{\mathcal{B}}$, respectively. Furthermore, let $\nu$ and $\mu$ be two probability distributions ... More
An idea for detecting capture dominated Dark StarsJun 22 2009I discuss an idea which could lead to a methodology for testing the effects of WIMP DM scattering and capture onto primordial stars. It relies on the effects of "life-prolongation" of affected Population III stars, that can slow down nuclear reactions ... More
Toward an invariant matrix model for the Anderson TransitionMar 11 2015We consider invariant matrix models with log-normal (asymptotic) weight. It is known that their eigenvalue distribution is intermediate between Wigner-Dyson and Poissonian, which candidates these models for describing a system intermediate between the ... More
An operator view on alliances in politicsJan 23 2015We introduce the concept of an {\em operator decision making technique} and apply it to a concrete political problem: should a given political party form a coalition or not? We focus on the situation of three political parties, and divide the electorate ... More
On the Spontaneous Breaking of U(N) symmetry in invariant Matrix ModelsDec 19 2014Jul 28 2015Matrix Models are the most effective way to describe strongly interacting systems with many degrees of freedom. They have proven successful in describing very different settings, from nuclei spectra to conduction in mesoscopic systems, from holographic ... More
The axiom of choice, co-comprehension schema and redundancies in triposesFeb 12 2016We study the role of the axiom of choice and co-comprehention in second order encoding of first order predicates logic
Ramified Galois covers via monoidal functorsJul 19 2015May 08 2016We interpret Galois covers in terms of particular monoidal functors, extending the correspondence between torsors and fiber functors. As applications we characterize tame $G$-covers between normal varieties for finite and \'etale group schemes and we ... More
Transition probabilities for non self-adjoint Hamiltonians in infinite dimensional Hilbert spacesAug 11 2015In a recent paper we have introduced several possible inequivalent descriptions of the dynamics and of the transition probabilities of a quantum system when its Hamiltonian is not self-adjoint. Our analysis was carried out in finite dimensional Hilbert ... More
Convergence in $L^p$ for Feynman path integralsMar 19 2015Mar 22 2015We consider a class of Schrodinger equations with time-dependent smooth magnetic and electric potentials having a growth at infinity at most linear and quadratic, respectively. We study the convergence in $L^p$ with loss of derivatives, $1<p<\infty$, ... More
Some results on the dynamics and transition probabilities for non self-adjoint hamiltoniansFeb 25 2015We discuss systematically several possible inequivalent ways to describe the dynamics and the transition probabilities of a quantum system when its hamiltonian is not self-adjoint. In order to simplify the treatment, we mainly restrict our analysis to ... More
Trace map and regularity of finite extensions of a DVRJun 13 2015We interpret the regularity of a finite and flat extension of a discrete valuation ring in terms of the trace map of the extension.
Homogeneous Hermitian manifolds and special metricsAug 29 2016We consider non-Kaehler compact complex manifolds which are homogeneous under the action of a compact Lie group of biholomorphisms and we investigate the existence of special (invariant) Hermitian metrics on these spaces. We focus on a particular class ... More
Non self-adjoint Hamiltonians with complex eigenvaluesMar 07 2016Motivated by what one observes dealing with PT-symmetric quantum mechanics, we discuss what happens if a physical system is driven by a diagonalizable Hamiltonian with not all real eigenvalues. In particular, we consider the functional structure related ... More
Hilbertian Toposes Epsilon ToposesMar 02 2016We study Hilbert's epsilon calculus and Hilbert's partial epsilon calculus in toposes.
Remarks on the Tripos To Topos Construction: extensionality, comprehensions, quotients and cauchy-complete objectsJan 30 2014Feb 24 2014We give a description of the Tripos To Topos construction in terms of four free constructions. We prove that these compose up to give a free construction from the category of triposes and logical morphisms to the category of toposes and logical functors. ... More
Universal scaling of gluon and ghost propagators in the infraredJul 07 2016A universal behavior is predicted for ghost and gluon propagators in the infrared. The universal behavior is shown to be a signature of a one-loop approximation and emerges naturally by the massive expansion that predicts universal analytical functions ... More
Dual Affine Quantum GroupsDec 03 1997Sep 13 1999Let $\hat{\frak g}$ be an untwisted affine Kac-Moody algebra, with its Sklyanin-Drinfel'd structure of Lie bialgebra, and let $\hat{\frak h}$ be the dual Lie bialgebra. By dualizing the quantum double construction - via formal Hopf algebras - we construct ... More
Quantization of Poisson GroupsNov 24 1995Jan 29 1996The quantization of well-known pairs of Poisson groups of a wide class is studied by means of Drinfeld's double construction and dualization via formal Hopf algebras; new quantized enveloping algebras $ U_{q,\varphi}^{M,\infty} (\frak h) $ and quantum ... More
The quantum duality principleSep 14 1999Jun 07 2001The "quantum duality principle" states that the quantization of a Lie bialgebra - via a quantum universal enveloping algebra (QUEA) - provides also a quantization of the dual Lie bialgebra (through its associated formal Poisson group) - via a quantum ... More
Local E(11) and the gauging of the trombone symmetryJan 08 2010Mar 17 2010In any dimension, the positive level generators of the very-extended Kac-Moody algebra $E_{11}$ with completely antisymmetric spacetime indices are associated to the form fields of the corresponding maximal supergravity. We consider the local $E_{11}$ ... More
Truncations of the D9-brane action and type-I stringsJan 06 2003Jan 17 2003The low-energy effective action of type-I superstring theory in ten dimensions is obtained performing a truncation of type-IIB supergravity in a background where D9-branes are present. The open sector corresponds to the first order in the low-energy expansion ... More
All Couplings of Minimal Six-dimensional SupergravityJan 11 2001We describe the complete coupling of $(1,0)$ six-dimensional supergravity to tensor, vector and hypermultiplets. The generalized Green-Schwarz mechanism implies that the resulting theory embodies factorized gauge and supersymmetry anomalies, to be disposed ... More
Generalization of the linear r-matrix formulation through Loop coproductsOct 06 2009A new method for the construction of classical integrable systems, that we call loop coproduct formulation, is presented. We show that the linear r-matrix formulation, the Sklyanin algebras and the reflection algebras can be obtained as particular subcases ... More
Loop coproductsJul 28 2009In this paper we show that if $A$ is a Poisson algebra equipped with a set of maps $\Delta^{(i)}_\la:A \to A^{\otimes N}$ satisfying suitable conditions, then the images of the Casimir functions of $A$ under the maps $\Delta^{(i)}_\la$ (that we call "loop ... More
Spacecraft Attitude Stabilization with Piecewise-constant Magnetic Dipole MomentMay 15 2015In actual implementations of magnetic control laws for spacecraft attitude stabilization, the time in which Earth magnetic field is measured must be separated from the time in which magnetic dipole moment is generated. The latter separation translates ... More
Cold Feedback in Cooling-Flow Galaxy ClustersNov 07 2006We put forward an alternative view to the Bondi-driven feedback between heating and cooling of the intra-cluster medium (ICM) in cooling flow galaxies and clusters. We adopt the popular view that the heating is due to an active galactic nucleus (AGN), ... More
Quantum corrections to broken N=8 supergravityFeb 08 2013The discovery of the Higgs boson and the non-discovery (so far) of additional particles at the TeV scale underline our poor understanding of the hierarchy problems in the physics of the fundamental interactions. Loosely motivated by this consideration, ... More
Supersymmetry and gauge symmetry breaking with naturally vanishing vacuum energyNov 13 1995We review the construction of $N=1$ supergravity models where the Higgs and super-Higgs effects are simultaneously realized, with naturally vanishing classical vacuum energy and goldstino components along gauge-non-singlet directions: this situation is ... More
Variations of the stellar Initial Mass Function in Semi-Analytic Models: implications for the mass assembly of galaxies in the GAEA modelMar 08 2019A wealth of observations recently challenged the notion of a universal stellar initial mass function (IMF) by showing evidences in favour of a variability of this statistical indicator as a function of galaxy properties. I present predictions from the ... More
Yang-Mills ghost propagator in linear covariant gaugesMar 02 2019From first principles, using a screened expansion, a simple one-loop analytical expression is provided for the ghost propagator of pure SU(3) Yang-Mills theory in a generic linear covariant gauge. At variance with the Landau gauge, the ghost dressing ... More
A note on toric Deligne-Mumford stacksMay 25 2007Apr 08 2008We give a new description of the data needed to specify a morphism from a scheme to a toric Deligne-Mumford stack. The description is given in terms of a collection of line bundles and sections which satisfy certain conditions. As applications, we characterize ... More
The tree method for multidimensional q-Hahn and q-Racah polynomialsDec 22 2009We develop a tree method for multidimensional q-Hahn polynomials. We define them as eigenfunctions of a multidimensional q-difference operator and we use the factorization of this operator as a key tool. Then we define multidimensional q-Racah polynomials ... More
A duality principle for non-convex optimization in $\mathbb{R}^n$Mar 14 2019Apr 01 2019This article develops a duality principle for a class of optimization problems in $\mathbb{R}^n$. The results are obtained based on standard tools of convex analysis and on a well known result of Toland for D.C. optimization. Global sufficient optimality ... More
On the generalized method of lines and its proximal explicit and hyper-finite difference approachesApr 28 2019May 07 2019This article firstly develops a proximal explicit approach for the generalized method of lines. In such a method, the domain of the PDE in question is discretized in lines and the equation solution is written on these lines as functions of the boundary ... More
Nearly parallel $G_2$-structures with large symmetry groupMay 08 2019We prove the existence of a one-parameter family of nearly parallel $G_2$-structures on the manifold $S^3\times \mathbb R^4$, which are mutually non isomorphic and invariant under the cohomogeneity one action of the group $SU(2)^3$. This family connects ... More
Quantum function algebras as quantum enveloping algebrasJan 10 1997May 10 2017Inspired by a result in [Ga], we locate two $ k[q,q^{-1}] $-integer forms of $ F_q[SL(n+1)] $, along with a presentation by generators and relations, and prove that for $ q=1 $ they specialize to $ U({\mathfrak{h}}) $, where $ {\mathfrak{h}} $ is the ... More
On General Duality Principles for Non-Convex Variational Optimization with Applications to the Ginzburg-Landau System in SuperconductivityApr 17 2018Oct 10 2018This article develops duality principles applicable to non-convex models in the calculus of variations. The results here developed are applied to Ginzburg-Landau type equations. For the first and second duality principles, through an optimality criterion ... More
Multidimensional Hahn polynomials, intertwining functions on the symmetric group and Clebsch-Gordan coefficientsMay 06 2008We generalize a construction of Dunkl, obtaining a wide class intertwining functions on the symmetric group and a related family of multidimensional Hahn polynomials. Following a suggestion of Vilenkin and Klymik, we develop a tree-method approach for ... More
On the radical of Brauer algebrasJun 20 2006Dec 14 2007The radical of the Brauer algebra B_f^x is known to be non-trivial when the parameter x is an integer subject to certain conditions (with respect to f). In these cases, we display a wide family of elements in the radical, which are explicitly described ... More
Moving closer: contractive maps on discrete metric spaces and graphsNov 18 2010We consider discrete metric spaces and we look for non-constant contractions. We introduce the notion of contractive map and we characterize the spaces with non-constant contractive maps. We provide some examples to discussion the possible relations between ... More
PBW theorems and Frobenius structures for quantum matricesOct 23 2006Dec 14 2007Let G be either of Mat(n), GL(n) or SL(n), let O_q(G) be the quantum function algebra - over Z[q,q^{-1}] - associated to G, and let O_e(G) be the specialisation of O_q(G) at a root of unity, of odd order l. Then O_e(G) is a module over the corresponding ... More
Presentation by Borel subalgebras and Chevalley generators for quantum enveloping algebrasMar 22 2004Dec 14 2007We provide an alternative approach to the Faddeev-Reshetikhin-Takhtajan presentation of the quantum group U_q(g), with L-operators as generators and relations ruled by an R-matrix. We look at U_q(g) as being generated by the quantum Borel subalgebras ... More
The $ R $--matrix action of untwisted affine quantum groups at roots of 1May 04 1998Jun 02 2017Let $\hat{\frak g}$ be an untwisted affine Kac-Moody algebra. The quantum group $U_h(\hat{\frak g})$ (over $\mathbb{C}[[h]]$) is known to be a quasitriangular Hopf algebra: in particular, it has a universal $ R $--matrix, which yields an $ R $--matrix ... More
Poisson geometrical symmetries associated to non-commutative formal diffeomorphismsSep 09 2003Dec 03 2004Let G be the group of all formal power series starting with x with coefficients in a field k of zero characteristic (with the composition product), and let F[G] be its function algebra. C. Brouder and A. Frabetti introduced a non-commutative, non-cocommutative ... More