Results for "Gabriele Sicuro"

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Groups, Information Theory and Einstein's Likelihood PrincipleNov 30 2015Apr 06 2016We propose a unifying picture where the notion of generalized entropy is related to information theory by means of a group-theoretical approach. The group structure comes from the requirement that an entropy be well defined with respect to the composition ... More
On the one dimensional Euclidean matching problem: exact solutions, correlation functions and universalityJun 29 2014We discuss the equivalence relation between the Euclidean bipartite matching problem on the line and on the circumference and the Brownian bridge process on the same domains. The equivalence allows us to compute the correlation function and the optimal ... More
Scaling hypothesis for the Euclidean bipartite matching problem II. Correlation functionsApr 02 2015We analyze the random Euclidean bipartite matching problem on the hypertorus in $d$ dimensions with quadratic cost and we derive the two--point correlation function for the optimal matching, using a proper ansatz introduced by Caracciolo et al. to evaluate ... More
Finite-size corrections in the random assignment problemFeb 20 2017May 17 2017We analytically derive, in the context of the replica formalism, the first finite size corrections to the average optimal cost in the random assignment problem for a quite generic distribution law for the costs. We show that, when moving from a power-law ... More
Quadratic stochastic Euclidean bipartite matching problemOct 08 2015Nov 27 2015We propose a new approach for the study of the quadratic stochastic Euclidean bipartite matching problem between two sets of $N$ points each, $N\gg 1$. The points are supposed independently randomly generated on a domain $\Omega\subset\mathbb R^d$ with ... More
Nonlinear inhomogeneous Fokker-Planck equations: entropy and free-energy time evolutionSep 20 2016We extend a recently introduced free-energy formalism for homogeneous Fokker-Planck equations to a wide, and physically appealing, class of inhomogeneous nonlinear Fokker-Planck equations. In our approach, the free-energy functional is expressed in terms ... More
Fluctuations in the random-link matching problemMay 21 2019Using the replica approach and the cavity method, we study the fluctuations of the optimal cost in the random-link matching problem. By means of replica arguments, we derive the exact expression of its variance. Moreover, we study the large deviation ... More
A foundational approach to the Lie theory for fractional order partial differential equationsMay 05 2014Mar 16 2016We provide a general theoretical framework allowing to extend the classical Lie theory for partial differential equations to the case of equations of fractional order. We propose a general prolongation formula allowing the study of Lie symmetries for ... More
On the connection between linear combination of entropies and linear combination of extremizing distributionsJan 29 2016Apr 30 2016We analyze the distribution that extremizes a linear combination of the Boltzmann--Gibbs entropy and the nonadditive $q$-entropy. We show that this distribution can be expressed in terms of a Lambert function. Both the entropic functional and the extremizing ... More
Anomalous scaling of the optimal cost in the one-dimensional random assignment problemMar 13 2018We consider the random Euclidean assignment problem on the line between two sets of $N$ random points, independently generated with the same probability density function $\varrho$. The cost of the matching is supposed to be dependent on a power $p>1$ ... More
A Theorem on the Existence of Symmetries of Fractional PDEsFeb 28 2014We propose a theorem that extends the classical Lie approach to the case of fractional partial differential equations (fPDEs) of the Riemann--Liouville type in (1+1) dimensions.
One-loop diagrams in the Random Euclidean Matching ProblemSep 29 2016Oct 01 2016The matching problem is a notorious combinatorial optimization problem that has attracted for many years the attention of the statistical physics community. Here we analyze the Euclidean version of the problem, i.e. the optimal matching problem between ... More
Random Euclidean matching problems in one dimensionJul 18 2017Sep 28 2017We discuss the optimal matching solution for both the assignment problem and the matching problem in one dimension for a large class of convex cost functions. We consider the problem in a compact set with the topology both of the interval and of the circumference. ... More
The Random Fractional Matching ProblemFeb 08 2018May 04 2018We consider two formulations of the random-link fractional matching problem, a relaxed version of the more standard random-link (integer) matching problem. In one formulation, we allow each node to be linked to itself in the optimal matching configuration. ... More
The Random Fractional Matching ProblemFeb 08 2018We consider two formulations of the random-link fractional matching problem, a relaxed version of the more standard random-link (integer) matching problem. In one formulation, we allow each node to be linked to itself in the optimal matching configuration. ... More
Scaling hypothesis for the Euclidean bipartite matching problemFeb 27 2014Aug 22 2014We propose a simple yet very predictive form, based on a Poisson's equation, for the functional dependence of the cost from the density of points in the Euclidean bipartite matching problem. This leads, for quadratic costs, to the analytic prediction ... More
On the robustness of the $q$-Gaussian familyJun 06 2015Oct 30 2015We introduce three deformations, called $\alpha$-, $\beta$- and $\gamma$-deformation respectively, of a $N$-body probabilistic model, first proposed by Rodr\'iguez et al. (2008), having $q$-Gaussians as $N\to\infty$ limiting probability distributions. ... More
Mean-field model for the density of states of jammed soft spheresApr 08 2018Jun 29 2018We propose a class of mean-field models for the isostatic transition of systems of soft spheres, in which the contact network is modeled as a random graph and each contact is associated to $d$ degrees of freedom. We study such models in the hypostatic, ... More
Universality of Power Law Coding for Principal NeuronsOct 21 2014In this paper we document distributions for spike rates, synaptic weights and neural gains for principal neurons in various tissues and under different behavioral conditions. We find a remarkable consistency of a power-law, specifically lognormal, distribution ... More
With raised eyebrows or the eyebrows raised ? A Neural Network Approach to Grammar Checking for DefinitenessJun 14 1996In this paper, we use a feature model of the semantics of plural determiners to present an approach to grammar checking for definiteness. Using neural network techniques, a semantics -- morphological category mapping was learned. We then applied a textual ... More
Boris Venkov's Theory of Lattices and Spherical DesignsJan 09 2012Boris Venkov passed away on November 10 2011 just 5 days before his 77th birthday. This article gives a short survey of the mathematical work of Boris Venkov in this direction.
Cosmological implications of Gamma Ray BurstsMay 30 2007The discovery that the bolometric energetics (and/or peak luminosity) of Gamma Ray Bursts correlates with their spectral properties has allowed to standardize the burst energetics to such a degree to enable their use for constraining the cosmological ... More
Gamma Ray Bursts: basic facts and ideasOct 14 2010The recent years witnessed a dramatic improvement in our knowledge of the phenomenology and physics of Gamma Ray Bursts (GRBs). However, our "pillars of knowledge" remain a few, while many aspects remain obscure and not understood. There is no general ... More
Emission processes in gamma-ray burstsJul 27 1999Recent results of the hectic research activity about gamma-ray bursts will be reviewed, with emphasis about the emission processes at the origin of the observed gamma-rays. The conventional synchrotron shock scenario is found to have problems, due to ... More
Internal shocks in blazar jetsJun 07 1999The discovery of strong gamma-ray and hard X-ray emission and the results from various multifrequency campaigns have disclosed new aspects of the blazar phenomenology, leading to a much more robust understanding of the mechanisms underlying their emission, ... More
X-Ray Emission in Gamma-Ray BlazarsDec 04 1996Although the gamma-ray emission in blazars dominates the power output, there are crucial informations carried by the X-rays. Indeed, their paucity, together with the short variability timescales observed both at X and gamma-ray energies constrains the ... More
Quadratic forms and Clifford algebras on derived stacksSep 07 2013Jun 15 2016In this paper we present an approach to quadratic structures in derived algebraic geometry. We define derived n-shifted quadratic complexes, over derived affine stacks and over general derived stacks, and give several examples of those. We define the ... More
Modeling and Analysis of a Two-Phase Thin Film Model with Insoluble SurfactantJul 05 2016In this paper we consider a two-phase thin film consisting of two immiscible viscous fluids endowed with a layer of insoluble surfactant on the surface of the upper fluid. The governing equations for the two film heights and the surfactant concentration ... More
Characterisation of dust events on Earth and Mars: the ExoMars/DREAMS experiment and the field campaigns in the Sahara desertDec 25 2018Atmospheric dust plays an important role on the terrestrial climate, regulating the amount of solar radiation coming to the surface, affecting the development and the life time of the clouds and providing fundamental nutrients to the growth of the terrestrial ... More
A criterion of convergence in the augmented Teichmueller spaceFeb 14 2008We prove a criterion of convergence in the augmented Teichmueller space that can be phrased in terms of convergence of the hyperbolic metrics or of quasiconformal convergence away from the nodes.
A remark on the virtual homotopical dimension of some moduli spaces of stable Riemann surfacesFeb 06 2006Oct 29 2007Inspired by his vanishing results of tautological classes and by Harer's computation of the virtual cohomological dimension of the mapping class group, Looijenga conjectured that the moduli space of smooth Riemann surfaces admits a stratification by affine ... More
The contact property for nowhere vanishing magnetic fields on the two-sphereAug 09 2013Feb 03 2015In this paper we give some positive and negative results about the contact property for the energy levels $\Sigma_c$ of a symplectic magnetic field on $S^2$. In the first part we focus on the case of the area form on a surface of revolution. We state ... More
Equidistribution and counting of orbit points for discrete rank one isometry groups of Hadamard spacesAug 09 2018Let $X$ be a proper, geodesically complete Hadamard space, and $\ \Gamma<\mbox{Is}(X)$ a discrete subgroup of isometries of $X$ with the fixed point of a rank one isometry of $X$ in its infinite limit set. In this paper we prove that if $\Gamma$ has non-arithmetic ... More
The Stable Trapping Phenomenon for Black Strings and Black Rings and its Obstructions on the Decay of Linear WavesSep 20 2018The geometry of solutions to the higher dimensional Einstein vacuum equations presents aspects that are absent in four dimensions, one of the most remarkable being the existence of stably trapped null geodesics in the exterior of asymptotically flat black ... More
Growth of conjugacy classes of Schottky groups in higher rank symmetric spacesDec 14 2005Let $X$ be a globally symmetric space of noncompact type, and $\Gamma\subset\Isom(X)$ a Schottky group of axial isometries. Then $M:=X/\Gamma$ is a locally symmetric Riemannian manifold of infinite volume. The goal of this note is to give an asymptotic ... More
On the Structure of Bispecial Sturmian WordsNov 19 2013A balanced word is one in which any two factors of the same length contain the same number of each letter of the alphabet up to one. Finite binary balanced words are called Sturmian words. A Sturmian word is bispecial if it can be extended to the left ... More
The covariogram and Fourier-Laplace transform in $\mathbb{C}^n$Dec 30 2013Apr 29 2016The covariogram $g_{K}$ of a convex body $K$ in $\mathbb{R}^n$ is the function which associates to each $x\in\mathbb{R}^n$ the volume of the intersection of $K$ with $K+x$. Determining $K$ from the knowledge of $g_K$ is known as the Covariogram Problem. ... More
Volumes of random 3-manifoldsMay 13 2019We prove a law of large numbers for the volumes of families of random hyperbolic mapping tori and Heegaard splittings providing a sharp answer to a conjecture of Dunfield and Thurston.
From Type II string theory towards BSM/dark sector physicsSep 30 2016Four-dimensional compactifications of string theory provide a controlled set of possible gauge representations accounting for BSM particles and dark sector components. In this review, constraints from perturbative Type II string compactifications in the ... More
The Radio Jet Velocities at High ResolutionFeb 10 2003The different methods to derive the jet velocity and orientation on the parsec scale are presented. From these methods I will discuss the velocity distribution of parsec scale jets and the possible presence of acceleration or deceleration in the jet velocity. ... More
The high energy view of blazarsAug 29 2003Beppo}SAX contributed substantially to our understanding of the physics of blazars. This has been made possible mainly by its wide energy range and especially by its high energy detector. Together with the information coming from still higher energies ... More
Collisional relaxation in a fermionic gasApr 12 1999We propose a method to study the degeneracy of a trapped atomic gas of fermions through the relaxation of the motion of a test particle. In the degenerate regime, and for an energy of the test particle well below the Fermi energy, we show that the Fermi-Dirac ... More
UV Completions of Partial Compositeness: The Case for a SU(4) Gauge GroupApr 28 2014We present a model of partial compositeness arising as the IR limit of a SU(4) gauge theory with only fermionic matter. This group is one of the most promising ones among a handful of possible choices allowing a symmetry breaking pattern incorporating ... More
Gitter und ModulformenNov 15 2002A main goal in lattice theory is the construction of dense lattices. Most of the remarkable dense lattices in small dimensions have an additional symmetry, they are modular, i.e. similar to their dual lattice. Extremal lattices are densest modular lattices, ... More
Riemann surfaces, ribbon graphs and combinatorial classesMay 12 2007This survey paper begins with the description of the duality between arc systems and ribbon graphs embedded in a punctured surface. Then we explain how to cellularize the moduli space of curves in two different ways: using Jenkins-Strebel differentials ... More
On the Chow ring of the classifying stack of PGL_3Apr 14 1999We compute generators for the Chow ring of the classifying space of PGL_3 (over the complex numbers) as defined by Totaro. We also find enough relations after inverting 3. We show that this ring is not generated by Chern classes (this is the first example ... More
Counterexamples to the local-global divisibility over elliptic curvesMay 04 2017Let $p \geq 5$ be a prime number. We find all the possible subgroups $G$ of ${\rm GL}_2 ( \mathbb{Z} / p \mathbb{Z} )$ such that there exists a number field $k$ and an elliptic curve ${\mathcal{E}}$ defined over $k$ such that the ${\rm Gal} ( k ( {\mathcal{E}}[p] ... More
A fourth extremal even unimodular lattice of dimension 48Dec 13 2013Jan 02 2014We show that there is a unique extremal even unimodular lattice of dimension 48 which has an automorphism of order 5 of type 5-(8,16)-8. Since the three known extremal lattices do not admit such an automorphism, this provides a new example of an extremal ... More
The covariogram determines three-dimensional convex polytopesMay 12 2008The cross covariogram g_{K,L} of two convex sets K, L in R^n is the function which associates to each x in R^n the volume of the intersection of K with L+x. The problem of determining the sets from their covariogram is relevant in stochastic geometry, ... More
From physical principles to relativistic classical Hamiltonian and Lagrangian particle mechanicsMar 15 2015We show that classical particle mechanics (Hamiltonian and Lagrangian consistent with relativistic electromagnetism) can be derived from three fundamental assumptions: infinite reducibility, deterministic and reversible evolution, and kinematic equivalence. ... More
Observational Properties of Jets in Active Galactic NucleiJun 04 2004Parsec scale jet properties are shortly presented and discussed. Observational data are used to derive constraints on the jet velocity and orientation, the presence of velocity structures, and the connection between the pc and kpc scale. Two peculiar ... More
Collision-assisted Zeeman cooling of neutral atomsApr 14 2000We propose a new method to cool gaseous samples of neutral atoms. The gas is confined in a non dissipative optical trap in the presence of an homogeneous magnetic field. The method accumulates atoms in the $m_F=0$ Zeeman sub-level. Cooling occurs via ... More
The jet/disk connection in blazarsFeb 24 2010Feb 28 2010The new high energy data coming mainly from the Fermi and Swift satellites and from the ground based Cerenkov telescopes are making possible to study not only the energetics of blazar jets, but also their connection to the associated accretion disks. ... More
MeV synchrotron BL LacsDec 22 1998The recent BeppoSAX observations of the BL Lac objects Mkn 501 and 1ES 2344+514 have shown that the synchrotron spectrum of these objects peaks, in a v-vF(v) representation, at energies at or above 100 keV. One can wonder if these are the most extreme ... More
Derived critical loci I - BasicsSep 23 2011We will quickly explore the derived geometry of zero loci of sections of vector bundles, with particular emphasis on derived critical loci. In particular we will single out many of the derived geometric structures carried by derived critical loci: the ... More
A model structure on relative dg-Lie algebroidsApr 22 2013Sep 05 2014In this Note, for the future purposes of relative formal derived deformation theory and of derived coisotropic structures, we prove the existence of a model structure on the category of dg-Lie algebroids over a cochain differential non-positively graded ... More
The Critical Exponents Of The Matrix Valued Gross-Neveu ModelJul 09 1996We study the large N limit of the MATRIX valued Gross-Neveu model in 2<d<4 dimensions. The method employed is a combination of the approximate recursion formula of Polyakov and Wilson with the solution to the zero dimensional large N counting problem ... More
Automorphisms of extremal unimodular lattices in dimension 72Sep 30 2014The paper narrows down the possible automorphisms of extremal even unimodular lattices of dimension 72. With extensive computations in {\sc Magma} using the very sophisticated algorithm for computing class groups of algebraic number fields written by ... More
Connectivity through bounds for the Castelnuovo-Mumford regularityDec 18 2014Jan 27 2015We present a simple method to obtain information regarding the connectivity of the 1-skeleta of a wide family of simplicial complexes through bounds for the Castelnuovo-Mumford regularity of their Stanley-Reisner rings. In this way we generalize and unify ... More
Transfer Functions for Protein Signal Transduction: Application to a Model of Striatal Neural PlasticityAug 05 2012Feb 24 2013We present a novel formulation for biochemical reaction networks in the context of signal transduction. The model consists of input-output transfer functions, which are derived from differential equations, using stable equilibria. We select a set of 'source' ... More
Network Topology influences Synchronization and Intrinsic Read-outJul 25 2005Aug 25 2016What are the effects of neuromodulation on a large network model? Neuromodulation influences neural processing by presynaptic and postsynaptic regulation of synaptic efficacy and by ion channel regulation for dendritic excitability. We present a model, ... More
On blocks with cyclic defect group and their head ordersNov 04 2003It is shown that Section 8 of Plesken's 1983 lecture notes describes blocks of cyclic defect group up to Morita equivalence. In particular such a block is determined by its planar embedded Brauer tree. Applying the radical idealizer process, the head ... More
Nonlinear variational problems with lack of compactnessJan 24 2019In this thesis we deal with two different classes of variational problems: 1) the problem of closed curves with prescribed curvature, or $H$-loop problem; 2) the study of the nodal solutions of the fractional Brezis-Nirenberg problem. In both cases we ... More
The contact property for magnetic flows on surfacesMay 13 2018This is the author's PhD Thesis (University of Cambridge, 2014) in its original form. In the first part, using an invariance result, we compute the symplectic homology of contact-type energy levels for magnetic systems on surfaces, provided the energy ... More
Poisson structures on the Teichmueller space of hyperbolic surfaces with conical pointsDec 09 2008Apr 15 2009In this paper two Poisson structures on the moduli space of hyperbolic surfaces with conical points are compared: the Weil-Petersson one and the \eta coming from the representation variety. We show that they are multiple of each other, if the angles do ... More
Riemann surfaces with boundary and natural triangulations of the Teichmueller spaceApr 03 2008Jun 06 2008We compare some natural triangulations of the Teichm\"uller space of hyperbolic surfaces with geodesic boundary and of some bordifications. We adapt Scannell-Wolf's proof to show that grafting semi-infinite cylinders at the ends of hyperbolic surfaces ... More
Asymptotic geometry and growth of conjugacy classes of nonpositively curved manifoldsAug 18 2005Mar 20 2006Let X be a Hadamard manifold and $\Gamma$ a discrete group of isometries of X which contains an axial isometry without invariant flat half plane. We study the behavior of conformal densities on the geometric limit set of $\Gamma$ in order to derive a ... More
On the cohomological dimension of the moduli space of Riemann surfacesMay 12 2014Mar 20 2017The moduli space of Riemann surfaces of genus $g\geq 2$ is (up to a finite \'etale cover) a complex manifold and so it makes sense to speak of its Dolbeault cohomological dimension. The conjecturally optimal bound is $g-2$. This expectation is verified ... More
Quasi-hereditary covers of higher zigzag-algebrasFeb 28 2018The aim of this paper is to define and study some quasi-hereditary covers for higher zigzag algebras. We will show how these algebras satisfy three different Koszul properties: they are Koszul in the classical sense, standard Koszul and Koszul with respect ... More
Generalized conformal densities for higher products of rank one Hadamard spacesMar 18 2014Let $X$ be a product of locally compact rank one Hadamard spaces and $\Gamma$ a discrete group of isometries which contains two elements projecting to a pair of independent rank one isometries in each factor. In [arXiv:1308.5584] we gave a precise description ... More
Geometry and Dynamics of Discrete Isometry Groups of Higher Rank Symmetric SpacesAug 29 2005For real hyperbolic spaces, the dynamics of individual isometries and the geometry of the limit set of nonelementary discrete isometry groups have been studied in great detail. Most of the results were generalised to discrete isometry groups of simply ... More
Factorizations of the Fibonacci Infinite WordAug 27 2015The aim of this note is to survey the factorizations of the Fibonacci infinite word that make use of the Fibonacci words and other related words, and to show that all these factorizations can be easily derived in sequence starting from elementary properties ... More
Higher order Dehn functions for horospheres in products of Hadamard spacesAug 10 2015Let $X$ be a product of $r$ locally compact Hadamard spaces. In this note we prove that the horospheres in $X$ centered at regular boundary points of $X$ are Lipschitz-$(r-2)$-connected. Using the filling construction by R.~Young in \cite{MR3268779} this ... More
Asymptotic Geometry in the product of Hadamard spaces with rank one isometriesDec 10 2008Mar 12 2010In this article we study asymptotic properties of certain discrete groups $\Gamma$ acting by isometries on a product $\XX=\XX_1\times \XX_2$ of locally compact Hadamard spaces. The motivation comes from the fact that Kac-Moody groups over finite fields, ... More
Lecture notes on closed orbits for twisted autonomous Tonelli Lagrangian flowsMay 01 2016These notes were prepared in occasion of a mini-course given by the author at the "CIMPA Research School - Hamiltonian and Lagrangian Dynamics" (10-19 March 2015 - Salto, Uruguay). The talks were meant as an introduction to the problem of finding periodic ... More
A linear time algorithm to compute the impact of all the articulation pointsApr 01 2015May 10 2015The articulation points of an undirected connected graphs are those vertices whose removal increases the number of connected components of the graph, i.e. the vertices whose removal disconnects the graph. However, not all the articulation points are equal: ... More
Blazars in hard X-raysFeb 11 2009Although blazars are thought to emit most of their luminosity in the gamma-ray band, there are subclasses of them very prominent in hard X-rays. These are the best candidates to be studied by Simbol-X. They are at the extremes of the blazar sequence, ... More
Blazars: recent developmentsOct 15 1998Recent observational and theoretical results on blazars are presented and discussed. We are beginning to understand the rich phenomenology of blazars, and we are finding trends which will hopefully lead us to unveil the physics of these extreme sources. ... More
The power of jets: blazars vs galactic superluminalsSep 28 1998Estimates on different scales of the power of relativistic bulk motion in extragalactic and galactic jets are presented. The power in the jets and the power produced by the accretion disk are found to be roughly equal. This may suggest an important role ... More
Radiative Processes in High Energy AstrophysicsFeb 22 2012Contents: Some Fundamental definitions; Bremsstrahlung and black body; Beaming; Synchrotron emission and absorption; Compton scattering; Synchrotron Self-Compton; Pairs; Active Galactic Nuclei.
Extragalactic Gamma--Rays: Gamma Ray Bursts and BlazarsNov 04 2004The extragalactic gamma-ray sky is dominated by two classes of sources: Gamma-Ray Bursts (GRBs) and radio loud active galactic nuclei whose jets are pointing at us (blazars). We believe that the radiation we receive from them originates from the transformation ... More
Generating green to red light with semiconductor lasersJan 04 2007Diode lasers enable one to continuously cover the 730 to 1100 nm range as well as the 370 to 550 nm range by frequency doubling, but a large part of the electro-magnetic spectrum spanning from green to red remains accessible only through expensive and ... More
A note on the cotangent complex in derived algebraic geometryAug 03 2010Sep 02 2010This note is supposed to answer some questions on deformation theory in derived algebraic geometry. We show that derived algebraic geometry allows for a geometrical interpretation of the full cotangent complex and gives a natural setting for deformation ... More
A Wilson-Majorana Regularization for Lattice Chiral Gauge TheoriesOct 04 1996Jan 29 1998We discuss the regularization of chiral gauge theories on the lattice introducing only physical degrees of freedom. This is obtained by writing the Wilson term in a Majorana form, at the expense of the U(1) symmetry related to fermion number conservation. ... More
Gauge theories of Partial Compositeness: Scenarios for Run-II of the LHCApr 21 2016Jun 08 2016We continue our investigation of gauge theories in which the Higgs boson arises as a pseudo-Nambu-Goldstone boson (pNGB) and top-partners arise as bound states of three hyperfermions. All models have additional pNGBs in their spectrum that should be accessible ... More
A new stable basis for RBF approximationOct 05 2012It's well know that Radial Basis Function approximants suffers of bad conditioning if the simple basis of translates is used. A recent work of M.Pazouki and R.Schaback gives a quite general way to build stable, orthonormal bases for the native space based ... More
Horn Binary Serialization AnalysisJul 15 2016A bit layout is a sequence of fields of certain bit lengths that specifies how to interpret a serial stream, e.g., the MP3 audio format. A layout with variable length fields needs to include meta-information to help the parser interpret unambiguously ... More
Triangulated Riemann surfaces with boundary and the Weil-Petersson Poisson structureOct 23 2006Jan 15 2009Given a Riemann surface with boundary S, the lengths of a maximal system of disjoint simple geodesic arcs on S that start and end at the boundary of S perpendicularly are coordinates on the Teichmueller space T(S). We compute the Weil-Petersson Poisson ... More
A sketchy note on enriched homotopical topologies and enriched homotopical stacksJul 21 2005This rough note describes some attempts to define a notion of enriched topology (and the associated theory of enriched stacks) on a category enriched over a symmetric monoidal model category, and poses some related questions.
Strongly modular lattices with long shadowNov 15 2002We classify strongly modular lattices with longest and second longest possible shadow.
Combinatorial classes on the moduli space of curves are tautologicalMar 17 2003Apr 26 2004The combinatorial description via ribbon graphs of the moduli space of Riemann surfaces makes it possible to define combinatorial cycles in a natural way. Witten and Kontsevich first conjectured that these classes are polynomials in the tautological classes. ... More
The cross covariogram of a pair of polygons determines both polygons, with a few exceptionsMay 13 2008The cross covariogram g_{K,L} of two convex sets K and L in R^n is the function which associates to each x in R^n the volume of the intersection of K and L+x. Very recently Averkov and Bianchi [AB] have confirmed Matheron's conjecture on the covariogram ... More
A Characterization of Bispecial Sturmian WordsApr 07 2012Jun 18 2012A finite Sturmian word w over the alphabet {a,b} is left special (resp. right special) if aw and bw (resp. wa and wb) are both Sturmian words. A bispecial Sturmian word is a Sturmian word that is both left and right special. We show as a main result that ... More
Weak solutions to a two-phase thin film model with insoluble surfactant driven by capillary effectsAug 29 2016Of concern is the study of a system of three equations describing the motion of a viscous complete wetting two-phase thin film endowed with a layer of insoluble surfactant on the surface of the upper fluid under the effects of capillary forces. The governing ... More
Brown-Peterson spectra in stable A^1-homotopy theoryApr 09 2000Apr 12 2000We characterize ring spectra morphisms from the algebraic cobordism spectrum $\QTR{Bbb}{MGL}$ (\QCITE{cite}{}{Vo1}) to an oriented spectrum $\QTR{Bbb}{E}$ (in the sense of Morel \QCITE{cite}{}{Mo}) via formal group laws on the ''topological'' subring ... More
From physical principles to classical Hamiltonian mechanicsJul 17 2014Oct 01 2014We derive the Hamiltonian formulation of classical mechanics directly, without reference to Lagrangian mechanics. We start from the definition of states in terms of labels used to identify them, and show how, under a deterministic and reversible process, ... More
Blazar jets: the spectraNov 20 2000The radiation observed by blazars is believed to originate from the transformation of bulk kinetic energy of relativistic jets into random energy. A simple way to achieve this is to have an intermittent central power source, producing shells of plasma ... More
Special Relativity at action in the UniverseMay 14 1999Nature succeeds in accelerating extended and massive objects to relativistic velocities. Jets in Active Galactic Nuclei and in galactic superluminal sources and gamma-ray bursts fireballs have bulk Lorentz factors from a few to several hundreds. A variety ... More
Extreme blazarsDec 10 1998The recent Cherenkov telescope observations and detections of the BL Lac objects Mkn 421, Mkn 501, 1ES 2344+514, PKS 2155--304 and possibly 1ES 1959+658 have shown that there exists a subclass of BL Lac objects emitting a substantial fraction of their ... More
Unification of all BlazarsJun 20 1997The overall spectra (SED) of blazars, from radio to gamma-ray energies, seem to obey well defined trends, with a continuity of properties between blazars of different classes. To quantify this statement we can either investigate their observed properties ... More