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Connection between In Medium Nucleon Form Factors and Deep Inelastic Structure FunctionsJan 16 2006Jan 23 2006We present a connection between the modifications induced by the nuclear medium of the nucleon form factors and of the deep inelastic structure functions, obtained using the concept of generalized parton distributions. Generalized parton distributions ... More

PQCD Analysis of Parton-Hadron DualityAug 16 2011We propose an extraction of the running coupling constant of QCD in the infrared region from experimental data on deep inelastic inclusive scattering at Bjorken x -> 1. We first attempt a perturbative fit of the data that extends NLO PQCD evolution to ... More

The Scale Dependence of Inclusive ep Scattering in the Resonance RegionJun 18 2000We examine the scale dependence in the resonance region of inclusive ep scattering. In particular we discuss the invariants other than Q^2, which have been proposed as a scale for pQCD evolution in a kinematical regime where both infrared singularities ... More

Exclusive Pion-production and the Relation to TransversityJul 15 2008Exclusive $\pi^0$ electroproduction from nucleons is suggested for extracting the tensor charge and other quantities related to transversity from experimental data. This process isolates C-parity odd and chiral odd combinations of t-channel exchange quantum ... More

Pseudoscalar Meson Electroproduction and TranversitySep 03 2010Exclusive meson leptoproduction from nucleons in the deeply virtual exchanged boson limit can be described by generalized parton distributions (GPDs). Including spin dependence in the description requires 8 independent quark-parton and gluon-parton functions. ... More

Limitations on dispersion relations for Generalized Parton DistributionsAug 16 2009Deeply Virtual Compton Scattering and electroproduction of mesons involve amplitudes that are analytic in energy. Analyticity enables Dispersion Relations (DR's) for such amplitudes, relating real and imaginary parts. Lately it has been suggested that ... More

The Use of Dispersion Relations in Hard Exclusive Processes and the Partonic Interpretation of Deeply Virtual Compton ScatteringMay 28 2009Recently dispersion relations have been applied to hard exclusive processes such as deeply virtual Compton scattering, and a holographic principle was proposed that maps out the generalized parton distributions entering the soft matrix elements for the ... More

Probing Spin Dependent Parton Distributions though Deeply Virtual ProcessesOct 24 2015Spin and transverse momentum dependent parton distributions - Generalized Parton Distributions (GPDs) - are at the interface between the QCD structure of the hadrons and observable quantities. The GPDs are linear superpositions within helicity amplitudes. ... More

Angular momentum sum rule in nucleiAug 10 2010In this work we derive a sum rule for the angular momentum of a spin 1 hadronic system.

Self-Organizing Maps Parametrization of Deep Inelastic Structure Functions with Error DeterminationSep 26 2013We present and discuss a new method to extract parton distribution functions from hard scattering processes based on an alternative type of neural network, the Self-Organizing Map. Quantitative results including a detailed treatment of uncertainties are ... More

Lorentz Invariance and QCD Equation of Motion Relations for Generalized Parton Distributions and the Dynamical Origin of Proton Orbital Angular MomentumSep 18 2017Oct 06 2017We derive new Lorentz Invariance and Equation of Motion Relations between twist-three Generalized Parton Distributions (GPDs) and moments in the parton transverse momentum, $k_T$, of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs), ... More

Setting the scale for DIS at large Bjorken xJan 27 2011We discuss the extension of a systematic perturbative QCD based analysis to the x -> 1 region. After subtracting a number of effects that transcend NLO pQCD evolution, such as target mass corrections and large x resummation effects, the remaining power ... More

Nucleon Femtography from Exclusive ReactionsMar 20 2019Major breakthroughs over the last two decades have led us to access information on how the nucleon's mass, spin and mechanical properties are generated from its quark and gluon degrees of freedom. On one side, a theoretical framework has been developed ... More

A New Perspective on Parton Distributions in NucleiAug 22 2006We present recent progress on the study of the deep inelastic structure of nuclei that improves our current understanding of the mechanisms of nuclear modifications of parton distribution functions.

The Strong Coupling Constant from Hadron Structure PhenomenologyAug 28 2012We present recent developments on the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD. A number of experiments show a smooth transition from small to large scales given by the four-momentum transfer in ... More

Analysis of $α_s$ from the realization of quark-hadron dualityJul 16 2013We present an analysis of the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD in the context of the quark-hadron duality \`a la Bloom-Gilman. Our framework will be the unpolarized structure function of ... More

Deeply Virtual Exclusive Processes with CharmSep 07 2010We propose to investigate a largely unexplored sector that is unique to the formulation of hard exclusive processes in terms of GPDs, namely the electroproduction of strange and charmed mesons in the kinematical ranges of Jefferson Lab's 12 GeV upgrade, ... More

Extraction of the Ratio of the Neutron to Proton Structure Functions from Deep Inelastic ScatteringJun 05 1995We study the nuclear ($A$) dependence of the European Muon Collaboration (EMC) effect at high values of $x$ ($x \geq 0.6$). Our approach makes use of conventional nuclear degrees of freedom within the Relativistic Impulse Approximation. By performing ... More

Twist Three Generalized Parton Distributions for Orbital Angular MomentumJan 30 2016We study the orbital angular momentum contribution to the spin structure of the proton. It is well known that the quark and gluon spin contributions do not add up to the proton spin. We motivate the connection between the Generalized Transverse Momentum ... More

Hyperon Polarization, Transversity and LHC PhysicsDec 30 2011Jan 23 2012Longstanding puzzles in spin physics can be confronted at the high energies of the LHC. Will large s-quark and c-quark polarization be observed through heavy hyperon production? Top quarks are expected to have significant polarization - single spin asymmetries. ... More

Exclusive meson leptoproduction and spin dependent generalized parton distributionsAug 11 2010Exclusive meson leptoproduction from nucleons in the deeply virtual exchanged boson limit can be described by generalized parton distributions (GPDs). Including spin dependence in the description requires 8 independent quark-parton and gluon-parton functions. ... More

Accessing Generalized Transversity Distributions with Exclusive $π^o$ ElectroproductionAug 15 2009Exclusive $\pi^0$ electroproduction from nucleons at large $Q^2$ can be described by Generalized Parton Distributions (GPDs), particularly the chiral odd subset related to transversity. These GPDs can be accessed experimentally from various cross sections ... More

Partonic Interpretation of Generalized Parton DistributionsJun 01 2010Jun 08 2010Generalized Parton Distributions describe, within QCD factorization, the non perturbative component in the amplitudes for deeply virtual exclusive processes. However, in order for a partonic interpretation to hold, semi-disconnected diagrams should not ... More

Investigating Partons' Transverse Spin with Deep Inelastic Exclusive ExperimentsApr 29 2011We show how deeply virtual pseudoscalar meson production experiments single out the contribution of the four chiral odd quark-proton GPDs which are related to the so far elusive transversity distribution function, $h_1$. Furthermore, in the kinematical ... More

Exclusive Meson Electroproduction: GPDs, Regge and Dispersion RelationsApr 20 2009Exclusive pi0 electroproduction from nucleons at large photon virtuality can be described in terms of Generalized Parton Distributions, particularly the chiral odd subset. Chiral odd GPDs are related to transversity and can be accessed experimentally ... More

Transversity via Exclusive pi0 ElectroproductionOct 12 2008Oct 20 2008Exclusive pi0 electroproduction from nucleons can be related to transversity, the tensor charge, and other quantities related to transversity. This process isolates C-parity odd and chiral odd combinations of t-channel exchange quantum numbers. In a hadronic ... More

Bounds on the Equation of State of Neutron Stars from High Energy Deeply Virtual Exclusive ExperimentsDec 04 2018Jan 14 2019The recent detection of gravitational waves from merging neutron star events has opened a new window on the many unknown aspects of their internal dynamics. A key role in this context is played by the transition from baryon to quark matter described in ... More

Self-Orgazing Maps Parametrization of Parton Distribution FunctionsAug 12 2010We describe a new method to extract parton distribution functions both in the unpolarized and the polarized case, based on a type of neural networks, the Self-Organizing Maps. Initial quantitative results of our Next to Leading Order analysis are presented ... More

Nucleon Tensor Charge from Exclusive $π^o$ ElectroproductionMay 23 2008Feb 02 2009Exclusive $\pi^o$ electroproduction from nucleons is suggested for extracting the tensor charge and other quantities related to transversity from experimental data. This process isolates C-parity odd and chiral odd combinations of t-channel exchange quantum ... More

Chiral-Odd Generalized Parton Distributions from Exclusive pi^o ElectroproductionJul 12 2008Exclusive $\pi^o$ electroproduction is suggested for extracting both the tensor charge and the transverse anomalous magnetic moment from experimental data. A connection between partonic degrees of freedom, given in terms of Generalized Parton Distributions, ... More

Spin Physics: Session SummaryJul 26 2010We summarize the main results of the Spin Physics Working Group Sessions at DIS 2010, the XVIII International Workshop on Deep Inelastic Scattering and Related Subjects.

Generalized Wandzura Wilczek Relations and Orbital Angular MomentumFeb 21 2018New Lorentz Invariance Relations (LIRs) were presented between twist-three Generalized Parton Distributions (GPDs) and transverse momentum, $k_T$, moments of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs). By implementing both ... More

Generalized Parton Distributions and Transversity in Nucleons and NucleiMar 28 2005We present an exploratory study using generalized parton distributions of several observables related to transverse degrees of freedom in hadronic structure -- the nucleon transverse momentum, the transverse radius, or impact parameter, and the momentum ... More

Towards a Direct Measurement of the Quark Orbital Angular Momentum DistributionAug 03 2015We discuss two different definitions of partonic orbital angular momentum given in the literature in terms of the Fourier transform of a Wigner distribution, $F_{14}$, and a twist three generalized parton distribution, $\tilde{E}_{2T}$, respectively. ... More

A Systematic Study of Power Corrections from World Deep Inelastic Scattering MeasurementsSep 03 1998By performing an analysis in moment space using high statistics DIS world data, we extract the values of both the QCD parameter $\Lambda^{(4)}_{\bar{MS}}$ up to NLO and of the power corrections to the proton structure function, $F_2$. At variance with ... More

Exploring Nucleon Structure with the Self-Organizing Maps AlgorithmNov 10 2014We discuss the application of an alternative type of neural network, the Self-Organizing Map to extract parton distribution functions from various hard scattering processes.

$π^o$ Electroproduction and TransversityDec 14 2007Exclusive $\pi^o$ electroproduction and related processes are suggested to investigate the chiral odd transversity distributions of quarks in the transversely polarized nucleon, $h_1(x)$, and its first moment, the tensor charge. The connection between ... More

Generalized Parton Distributions from Hadronic Observables: Non-Zero SkewnessAug 02 2007May 28 2008We propose a physically motivated parametrization for the unpolarized generalized parton distributions, H and E, valid at both zero and non-zero values of the skewness variable, \zeta. Our approach follows a previous detailed study of the \zeta=0 case ... More

Beyond-Standard-Model Tensor Interaction and Hadron PhenomenologyMar 23 2015We evaluate the impact of recent developments in hadron phenomenology on extracting possible fundamental tensor interactions beyond the standard model. We show that a novel class of observables, including the chiral-odd generalized parton distributions, ... More

Observations of Chiral Odd GPDs and their ImplicationsSep 28 2013Our original suggestion to investigate exclusive $\pi^0$ electroproduction as a method for extracting the tensor charge, transversity, and other quantities related to chiral odd generalized parton distributions from cross section and asymmetry data is ... More

Parton Transverse Momentum and Orbital Angular Momentum DistributionsJan 22 2016The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined ... More

Strategies to Extract Generalized Parton Distributions from DataAug 15 2009A number of deeply virtual exclusive experiments will allow us to access the Generalized Parton Distributions which are embedded in the complex amplitudes for such processes. The extraction from experiment is particularly challenging both because of the ... More

Flexible Parametrization of Generalized Parton Distributions from Deeply Virtual Compton Scattering ObservablesDec 16 2010Feb 16 2011We present a physically motivated parametrization of the chiral-even generalized parton distributions in the non-singlet sector obtained from a global analysis using a set of available experimental data. Our analysis is valid in the kinematical region ... More

On a family of KP multi-line solitons associated to rational degenerations of real hyperelliptic curves and to the finite non-periodic Toda hierarchyMay 03 2016Jul 04 2016We classify the soliton data which may be associated to certain rational degenerations of regular hyperelliptic M-curves. Such soliton data correspond to a family of KP multi-line solitons in the totally positive part of the Grassmannian Gr(k,n) which ... More

On a family of KP multi-line solitons associated to rational degenerations of real hyperelliptic curves and to the finite non-periodic Toda hierarchyMay 03 2016Dec 17 2016We classify the soliton data in the totally non--negative part of Gr(k,n) which may be associated to algebraic-geometric data on certain rational degenerations of regular hyperelliptic M-curves. Such degenerate rational curve G is a desingularization ... More

Angular momentum sum rule for spin one hadronic systemsJan 03 2011Mar 05 2012We derive a sum rule for the total quark angular momentum of a spin-one hadronic system within a gauge invariant decomposition of the hadron's spin. We show that the total angular momentum can be measured through deeply virtual Compton scattering experiments ... More

Deeply Virtual Neutrino Production of $π^0$ from Nucleon and Nuclear TargetsNov 02 2009In most experiments aimed at determining the masses and mixing parameters for neutrino oscillations in different energy regimes there are strong backgrounds to neutrino interactions with matter that can confuse the expected small signals. One particular ... More

Flavor dependence of chiral odd generalized parton distributions and the tensor charge from the analysis of combined $π^0$ and $η$ exclusive electroproduction dataJan 02 2014Using a physically motivated parameterization based on the reggeized diquark model we perform a flavor separation of the chiral-odd generalized parton distributions obtained from both $\pi^0$ and $\eta$ exclusive electroproduction. In our approach we ... More

Easy as $π^o$: On the Interpretation of Recent Electroproduction ResultsJan 29 2012Jul 02 2012Exclusive $\pi^o$ electroproduction from nucleons was first suggested by Ahmad, Goldstein and Liuti for extracting from experimental data the tensor charge, transversity and other quantities related to chiral odd combinations of generalized parton distributions. ... More

Generalized Parton Distributions from Hadronic Observables: Zero SkewnessNov 03 2006Aug 31 2007We propose a physically motivated parametrization for the unpolarized generalized parton distributions. At zero value of the skewness variable, $\zeta$, the parametrization is constrained by simultaneously fitting the experimental data on both the nucleon ... More

Reciprocal transformations and local Hamiltonian structures of hydrodynamic type systemsMay 15 2008Feb 26 2009We start from a hyperbolic DN hydrodynamic type system of dimension $n$ which possesses Riemann invariants and we settle the necessary conditions on the conservation laws in the reciprocal transformation so that, after such a transformation of the independent ... More

An Analysis of the Asymptotic Limit of Gluon ShadowingMar 23 2000We examine the gluon distributions in nuclei in the asymptotic region defined by $Q^2 \to \infty$, $x \to 0$. An analysis using the Double Asymptotic Scaling variables of Ball and Forte is proposed. New scaling relations are predicted which can help disentangling ... More

Accidental $ξ$-scaling as a Signature of Nuclear Effects at $x>1$May 02 1995We propose an interpretation of the $\xi$-scaling behavior of nuclear structure functions observed at Bjorken $x>1$ and $Q^2 \lesssim 4 \, {\rm (GeV/c)^2}$. We show that at $\xi \gtrsim 1$, $\xi$-scaling might arise accidentally because of the approximate ... More

Consequences of Nuclear Shadowing for Heavy Quarkonium Production in Hadron-Nucleus InteractionsJul 11 1994We study nuclear shadowing in $J/\psi$ and $\Upsilon$ production in hadron-nucleus interactions and in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider. %We define the regions in $x_f$ where nuclear shadowing ... More

Partonic Picture of Generalized Transverse Momentum DistributionsSep 26 2013We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in ... More

Interpretation of the Flavor Dependence of Nucleon Form Factors in a Generalized Parton Distribution ModelJun 08 2012Sep 26 2013We give an interpretation of the $u$ and $d$ quarks contributions to the nucleon electromagnetic form factors for values of the four-momentum transfer in the multi-GeV region where flavor separated data have been recently made available. The data show, ... More

Identification of Observables for Quark and Gluon Orbital Angular MomentumDec 01 2014A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic ... More

On the Observability of the Quark Orbital Angular Momentum DistributionOct 18 2013Mar 18 2014We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in ... More

Microscopic Description of Deeply Virtual Compton Scattering off Spin-0 NucleiMay 13 2005We evaluate within a microscopic calculation the contributions of both coherent and incoherent deeply virtual Compton scattering from a spin-0 nucleus. The coherent contribution is obtained when the target nucleus recoils as a whole, whereas for incoherent ... More

Using FEMLAB for Gravitational problems: numerical simulations for allSep 26 2005We discuss the possibility to solve Modern Numerical Relativity problems using finite element methods (FEM). Adopting a "user friendly" software for handling totally general systems of nonlinear partial differential equations, FEMLAB, we model and numerically ... More

Modulation of Camassa--Holm equation and reciprocal transformationsJun 15 2005Nov 03 2005We derive the modulation equations or Whitham equations for the Camassa--Holm (CH) equation. We show that the modulation equations are hyperbolic and admit bi-Hamiltonian structure. Furthermore they are connected by a reciprocal transformation to the ... More

Nuclear Medium Modifications of Hadrons from Generalized Parton DistributionsApr 04 2005May 06 2005We study the structure of generalized parton distributions in spin 0 nuclei within a microscopic approach for nuclear dynamics. GPDs can be used on one side as tools to unravel the deep inelastic transverse structure of nuclei in terms of both transverse ... More

Generalized Parton Distributions and Color TransparencyMay 03 2004May 05 2004We study the structure of generalized parton distributions in impact parameter space with the aim of determining the size and role of small transverse separations components in the quarks wave function. We analyze the relation between transverse momentum ... More

Extraction of Generalized Parton Distribution Observables from Deeply Virtual Electron Proton Scattering ExperimentsMar 13 2019We provide the general expression of the cross section for exclusive deeply virtual photon electroproduction from a spin 1/2 target using current parameterizations of the off-forward correlation function in a nucleon for different beam and target polarization ... More

Laboratorio di matematica: una sintesi di contenuti e metodologieNov 09 2012In this paper, our aim is to discuss the outcome of a ten-year experimental workshop activity carried out by the Center `matematita' (http://www.matematita.it/) with classes of pre-university students of any age. We analyse the potential benefits of this ... More

Well-posed forms of the 3+1 conformally-decomposed Einstein equationsApr 19 1999We show that well-posed, conformally-decomposed formulations of the 3+1 Einstein equations can be obtained by densitizing the lapse and by combining the constraints with the evolution equations. We compute the characteristics structure and verify the ... More

KP theory, plane-bipartite networks in the disk and rational degenerations of M-curvesDec 30 2017We associate real and regular algebraic-geometric data to the class of multi-line soliton solutions of Kadomtsev-Petviashvili II (KP) equation whose asymptotic behavior in space-time has been recently classified using the combinatorial structure of the ... More

Central Limit Theorem for Coloured Hard-DimersJun 19 2009Using an averaged generating function for coloured hard-dimers, some random variables of interest are studied. The main result lies in the fact that all their probability distributions obey a central limit theorem.

Periodic billiard orbits on $n$--dimensional ellipsoids with impacts on confocal quadrics and isoperiodic deformationsMar 11 2009Apr 13 2009In our paper we study periodic geodesic motion on multidimensional ellipsoids with elastic impacts along confocal quadrics. We show that the method of isoperiodic deformation is applicable.

A noncommutative enumeration problemApr 10 2010Dec 06 2010In this article we tackle the combinatorics of coloured hard-dimer objects. This is achieved by identifying coloured hard-dimer configurations with a certain class of rooted trees that allow for an algebraic treatment in terms of noncommutative formal ... More

KP theory, plabic networks in the disk and rational degenerations of M--curvesDec 30 2017Mar 28 2019We complete the program of Ref. [3,5] of connecting totally non-negative Grassmannians to the reality problem in KP finite-gap theory via the assignment of real regular divisors on rational degenerations of M-curves for the class of real regular multi-line ... More

Reducible M-curves for Le-networks in the totally-nonnegative Grassmannian and KP-II multiline solitonsMay 15 2018Jul 30 2018We associate real and regular algebraic--geometric data to each multi--line soliton solution of Kadomtsev-Petviashvili II (KP) equation. These solutions are known to be parametrized by points of the totally non--negative part of real Grassmannians $Gr^{TNN}(k,n)$. ... More

Accuracy of the thin-lens approximation in strong lensing by smoothly truncated dark matter haloesMay 19 2011The accuracy of mass estimates by gravitational lensing using the thin-lens approximation applied to Navarro-Frenk-White mass models with a soft truncation mechanism recently proposed by Baltz, Marshall and Oguri is studied. The gravitational lens scenario ... More

Study of errors in strong gravitational lensingNov 30 2007We examine the accuracy of strong gravitational lensing determinations of the mass of galaxy clusters by comparing the conventional approach with the numerical integration of the fully relativistic null geodesic equations in the case of weak gravitational ... More

Closed geodesics and billiards on quadrics related to elliptic KdV solutionsDec 14 2004We consider algebraic geometrical properties of the integrable billiard on a quadric Q with elastic impacts along another quadric confocal to Q. These properties are in sharp contrast with those of the ellipsoidal Birkhoff billiards. Namely, generic complex ... More

Coloured Hard-DimersJun 18 2009An averaged generating function for coloured hard-dimers is being investigated by proving estimates for the latter. Furthermore, two different enumerating problems and their distributions are studied numerically.

A Perturbative QCD Based Study of Polarized Nucleon Structure in the Transition Region and Beyond: "Quarks, Color Neutral Clusters, and Hadrons"Dec 27 2004A large fraction of the world data on both polarized and unpolarized inclusive $ep$ scattering at large Bjorken $x$ lies in the resonance region where a correspondence with the deep inelastic regime, known as Bloom and Gilman's duality, was observed. ... More

GPD phenomenology and DVCS fitting - Entering the high-precision eraFeb 08 2016We review the phenomenological framework for accessing Generalized Parton Distributions (GPDs) using measurements of Deeply Virtual Compton Scattering (DVCS) from a proton target. We describe various GPD models and fitting procedures, emphasizing specific ... More

Quark-Hadron Duality in Structure FunctionsJan 14 2005Quark-hadron duality is studied in a systematic way for both the unpolarized and polarized structure functions, by taking into account all the available data in the resonance region.In both cases, a detailed perturbative QCD based analysis of the structure ... More

Parton-Hadron Duality in Unpolarised and Polarised Structure FunctionsAug 05 2003We study the phenomenon of parton-hadron duality in both polarised and unpolarised electron proton scattering using the HERMES and the Jefferson Lab data, respectively. In both cases we extend a systematic perturbative QCD based analysis to the integrals ... More

Self-Organizing Maps and Parton Distributions FunctionsAug 25 2010We present a new method to extract parton distribution functions from high energy experimental data based on a specific type of neural networks, the Self-Organizing Maps. We illustrate the features of our new procedure that are particularly useful for ... More

Rational degeneration of M-curves, totally positive Grassmannians and KP-solitonsJun 01 2015Jul 21 2015The aim of our paper is to connect two areas of mathematics: -The theory of totally positive Grassmannians; -The rational degenerations of the $M$-curves; using the finite--gap theory for solitons of the Kadomtsev-Petviashvili 2 (KP) equation. We associate ... More

Singularities of wavefronts and lightcones in the context of GR via null foliationsJun 21 2000We describe an approach to the issue of the singularities of null hypersurfaces, due to the focusing of null geodesics, in the context of the recently introduced formulation of GR via null foliations.

A variational principle for time of arrival of null geodesicsOct 20 1998Normally the issue or question of the time of arrival of light rays at an observer coming from a given source is associated with Fermat's Principle of Least Time which yields paths of extremal time. We here investigate a related but different problem. ... More

Rational degeneration of M-curves, totally positive Grassmannians and KP2-solitonsJun 01 2015Mar 19 2018We establish a new connection between the theory of totally positive Grassmannians and the theory of $\mathtt M$-curves using the finite--gap theory for solitons of the KP equation. Here and in the following KP equation denotes the Kadomtsev-Petviashvili ... More

Dynamics of Fermat potentials in non-perturbative gravitational lensingMay 03 2002We present a framework, based on the null-surface formulation of general relativity, for discussing the dynamics of Fermat potentials for gravitational lensing in a generic situation without approximations of any kind. Additionally, we derive two lens ... More

An Exact Universal Gravitational Lensing EquationOct 05 1998We first define what we mean by gravitational lensing equations in a general space-time. A set of exact relations are then derived that can be used as the gravitational lens equations in all physical situations. The caveat is that into these equations ... More

Real soliton lattices of KP-II and desingularization of spectral curves: the Gr^{TP}(2,4) caseMar 29 2018May 03 2018We apply the general construction developed in references [4,5] to the first non-trivial case of Gr^{TP}(2,4). In particular, we construct finite-gap KP-II real quasiperiodic solutions in the form of soliton lattice corresponding to a smooth genus 4 M-curve, ... More

Next steps in understanding the asymptotics of $3d$ quantum gravityDec 10 2014Based on a combinatorial approach and random matrix theory, we show a central limit theorem that gives important insight into causally triangulated $3d$ quantum gravity.

Photon detection efficiency of Geiger-mode avalanche photodiodesJun 16 2010The photon detection efficiencies of multi-pixel Geiger-mode avalanche photodiodes manufactured by different produ cers are estimated. A new fit method of the response spectra to low-intensity light, taking into ac count after-pulse and cross-talk effects ... More

Lorentzian Metrics from Characteristic SurfacesFeb 10 1995Feb 11 1995The following issue is raised and discussed; when do families of foliations by hypersurfaces on a given four dimensional manifold become the null surfaces of some unknown, but to be determined, metric $g_{ab}(x)$? It follows from these results that one ... More

GR via Characteristic SurfacesFeb 11 1995We reformulate the Einstein equations as equations for families of surfaces on a four-manifold. These surfaces eventually become characteristic surfaces for an Einstein metric (with or without sources). In particular they are formulated in terms of two ... More

Tagged EMC Measurements on Light NucleiAug 02 2017We propose to measure tagged deep inelastic scattering from light nuclei (deuterium and $^4$He) by detecting the low energy nuclear spectator recoil (p, $^3$H and $^3$He) in addition to the scattered electron. The proposed experiment will provide stringent ... More

Partonic Structure of Light NucleiAug 02 2017Aug 05 2017We propose to study the partonic structure of $^4$He by measuring the Beam Spin Asymmetry (BSA) in coherent Deeply Virtual Compton Scattering (DVCS) and the differential cross-section of the Deeply Virtual Meson Production (DVMP) of the $\phi$. Despite ... More

Isospin Dependence of Power Corrections in Deep Inelastic ScatteringApr 22 2003We present results of a perturbative QCD analysis of deep inelastic measurements of both the deuteron and proton structure functions. We evaluate the theoretical uncertainty associated to nuclear effects in the deuteron, and we extract simultaneously ... More

Demography of high redshift AGNSep 21 2011High redshift AGN holds the key to understand the early structure formation and to probe the Universe during its infancy. We review the latest searches for high-z AGN in the deepest X-ray field so far, the Chandra Deep Field South (CDFS) 4 Msecond exposure. ... More

Multimodal music information processing and retrieval: survey and future challengesFeb 14 2019Towards improving the performance in various music information processing tasks, recent studies exploit different modalities able to capture diverse aspects of music. Such modalities include audio recordings, symbolic music scores, mid-level representations, ... More

The complete spectrum of the area from recoupling theory in loop quantum gravityAug 16 1996Aug 29 1996We compute the complete spectrum of the area operator in the loop representation of quantum gravity, using recoupling theory. This result extends previous derivations, which did not include the ``degenerate'' sector, and agrees with the recently computed ... More

Differential Geometry from Differential EquationsDec 15 2000May 03 2001We first show how, from the general 3rd order ODE of the form z'''=F(z,z',z'',s), one can construct a natural Lorentzian conformal metric on the four-dimensional space (z,z',z'',s). When the function F(z,z',z'',s) satisfies a special differential condition ... More

Unraveling Violations of Parton-Hadron Duality in ep ScatteringMay 27 2002Recent studies of the Q^2 dependence of ep scattering in the large x region and in the Q^2 range: 1 < Q^2 <leq 30 Gev^2, confirm the validity of the phenomenon of quark-hadron duality - the similarity of the deep inelastic (parton) and resonance (hadron) ... More